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git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull hardening updates from Kees Cook:
"As is pretty normal for this tree, there are changes all over the
place, especially for small fixes, selftest improvements, and improved
macro usability.
Some header changes ended up landing via this tree as they depended on
the string header cleanups. Also, a notable set of changes is the work
for the reintroduction of the UBSAN signed integer overflow sanitizer
so that we can continue to make improvements on the compiler side to
make this sanitizer a more viable future security hardening option.
Summary:
- string.h and related header cleanups (Tanzir Hasan, Andy
Shevchenko)
- VMCI memcpy() usage and struct_size() cleanups (Vasiliy Kovalev,
Harshit Mogalapalli)
- selftests/powerpc: Fix load_unaligned_zeropad build failure
(Michael Ellerman)
- hardened Kconfig fragment updates (Marco Elver, Lukas Bulwahn)
- Handle tail call optimization better in LKDTM (Douglas Anderson)
- Use long form types in overflow.h (Andy Shevchenko)
- Add flags param to string_get_size() (Andy Shevchenko)
- Add Coccinelle script for potential struct_size() use (Jacob
Keller)
- Fix objtool corner case under KCFI (Josh Poimboeuf)
- Drop 13 year old backward compat CAP_SYS_ADMIN check (Jingzi Meng)
- Add str_plural() helper (Michal Wajdeczko, Kees Cook)
- Ignore relocations in .notes section
- Add comments to explain how __is_constexpr() works
- Fix m68k stack alignment expectations in stackinit Kunit test
- Convert string selftests to KUnit
- Add KUnit tests for fortified string functions
- Improve reporting during fortified string warnings
- Allow non-type arg to type_max() and type_min()
- Allow strscpy() to be called with only 2 arguments
- Add binary mode to leaking_addresses scanner
- Various small cleanups to leaking_addresses scanner
- Adding wrapping_*() arithmetic helper
- Annotate initial signed integer wrap-around in refcount_t
- Add explicit UBSAN section to MAINTAINERS
- Fix UBSAN self-test warnings
- Simplify UBSAN build via removal of CONFIG_UBSAN_SANITIZE_ALL
- Reintroduce UBSAN's signed overflow sanitizer"
* tag 'hardening-v6.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (51 commits)
selftests/powerpc: Fix load_unaligned_zeropad build failure
string: Convert helpers selftest to KUnit
string: Convert selftest to KUnit
sh: Fix build with CONFIG_UBSAN=y
compiler.h: Explain how __is_constexpr() works
overflow: Allow non-type arg to type_max() and type_min()
VMCI: Fix possible memcpy() run-time warning in vmci_datagram_invoke_guest_handler()
lib/string_helpers: Add flags param to string_get_size()
x86, relocs: Ignore relocations in .notes section
objtool: Fix UNWIND_HINT_{SAVE,RESTORE} across basic blocks
overflow: Use POD in check_shl_overflow()
lib: stackinit: Adjust target string to 8 bytes for m68k
sparc: vdso: Disable UBSAN instrumentation
kernel.h: Move lib/cmdline.c prototypes to string.h
leaking_addresses: Provide mechanism to scan binary files
leaking_addresses: Ignore input device status lines
leaking_addresses: Use File::Temp for /tmp files
MAINTAINERS: Update LEAKING_ADDRESSES details
fortify: Improve buffer overflow reporting
fortify: Add KUnit tests for runtime overflows
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 RFDS mitigation from Dave Hansen:
"RFDS is a CPU vulnerability that may allow a malicious userspace to
infer stale register values from kernel space. Kernel registers can
have all kinds of secrets in them so the mitigation is basically to
wait until the kernel is about to return to userspace and has user
values in the registers. At that point there is little chance of
kernel secrets ending up in the registers and the microarchitectural
state can be cleared.
This leverages some recent robustness fixes for the existing MDS
vulnerability. Both MDS and RFDS use the VERW instruction for
mitigation"
* tag 'rfds-for-linus-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
KVM/x86: Export RFDS_NO and RFDS_CLEAR to guests
x86/rfds: Mitigate Register File Data Sampling (RFDS)
Documentation/hw-vuln: Add documentation for RFDS
x86/mmio: Disable KVM mitigation when X86_FEATURE_CLEAR_CPU_BUF is set
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull core x86 updates from Ingo Molnar:
- The biggest change is the rework of the percpu code, to support the
'Named Address Spaces' GCC feature, by Uros Bizjak:
- This allows C code to access GS and FS segment relative memory
via variables declared with such attributes, which allows the
compiler to better optimize those accesses than the previous
inline assembly code.
- The series also includes a number of micro-optimizations for
various percpu access methods, plus a number of cleanups of %gs
accesses in assembly code.
- These changes have been exposed to linux-next testing for the
last ~5 months, with no known regressions in this area.
- Fix/clean up __switch_to()'s broken but accidentally working handling
of FPU switching - which also generates better code
- Propagate more RIP-relative addressing in assembly code, to generate
slightly better code
- Rework the CPU mitigations Kconfig space to be less idiosyncratic, to
make it easier for distros to follow & maintain these options
- Rework the x86 idle code to cure RCU violations and to clean up the
logic
- Clean up the vDSO Makefile logic
- Misc cleanups and fixes
* tag 'x86-core-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (52 commits)
x86/idle: Select idle routine only once
x86/idle: Let prefer_mwait_c1_over_halt() return bool
x86/idle: Cleanup idle_setup()
x86/idle: Clean up idle selection
x86/idle: Sanitize X86_BUG_AMD_E400 handling
sched/idle: Conditionally handle tick broadcast in default_idle_call()
x86: Increase brk randomness entropy for 64-bit systems
x86/vdso: Move vDSO to mmap region
x86/vdso/kbuild: Group non-standard build attributes and primary object file rules together
x86/vdso: Fix rethunk patching for vdso-image-{32,64}.o
x86/retpoline: Ensure default return thunk isn't used at runtime
x86/vdso: Use CONFIG_COMPAT_32 to specify vdso32
x86/vdso: Use $(addprefix ) instead of $(foreach )
x86/vdso: Simplify obj-y addition
x86/vdso: Consolidate targets and clean-files
x86/bugs: Rename CONFIG_RETHUNK => CONFIG_MITIGATION_RETHUNK
x86/bugs: Rename CONFIG_CPU_SRSO => CONFIG_MITIGATION_SRSO
x86/bugs: Rename CONFIG_CPU_IBRS_ENTRY => CONFIG_MITIGATION_IBRS_ENTRY
x86/bugs: Rename CONFIG_CPU_UNRET_ENTRY => CONFIG_MITIGATION_UNRET_ENTRY
x86/bugs: Rename CONFIG_SLS => CONFIG_MITIGATION_SLS
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 cleanups from Ingo Molnar:
"Misc cleanups, including a large series from Thomas Gleixner to cure
sparse warnings"
* tag 'x86-cleanups-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/nmi: Drop unused declaration of proc_nmi_enabled()
x86/callthunks: Use EXPORT_PER_CPU_SYMBOL_GPL() for per CPU variables
x86/cpu: Provide a declaration for itlb_multihit_kvm_mitigation
x86/cpu: Use EXPORT_PER_CPU_SYMBOL_GPL() for x86_spec_ctrl_current
x86/uaccess: Add missing __force to casts in __access_ok() and valid_user_address()
x86/percpu: Cure per CPU madness on UP
smp: Consolidate smp_prepare_boot_cpu()
x86/msr: Add missing __percpu annotations
x86/msr: Prepare for including <linux/percpu.h> into <asm/msr.h>
perf/x86/amd/uncore: Fix __percpu annotation
x86/nmi: Remove an unnecessary IS_ENABLED(CONFIG_SMP)
x86/apm_32: Remove dead function apm_get_battery_status()
x86/insn-eval: Fix function param name in get_eff_addr_sib()
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 SEV updates from Borislav Petkov:
- Add the x86 part of the SEV-SNP host support.
This will allow the kernel to be used as a KVM hypervisor capable of
running SNP (Secure Nested Paging) guests. Roughly speaking, SEV-SNP
is the ultimate goal of the AMD confidential computing side,
providing the most comprehensive confidential computing environment
up to date.
This is the x86 part and there is a KVM part which did not get ready
in time for the merge window so latter will be forthcoming in the
next cycle.
- Rework the early code's position-dependent SEV variable references in
order to allow building the kernel with clang and -fPIE/-fPIC and
-mcmodel=kernel
- The usual set of fixes, cleanups and improvements all over the place
* tag 'x86_sev_for_v6.9_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (36 commits)
x86/sev: Disable KMSAN for memory encryption TUs
x86/sev: Dump SEV_STATUS
crypto: ccp - Have it depend on AMD_IOMMU
iommu/amd: Fix failure return from snp_lookup_rmpentry()
x86/sev: Fix position dependent variable references in startup code
crypto: ccp: Make snp_range_list static
x86/Kconfig: Remove CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
Documentation: virt: Fix up pre-formatted text block for SEV ioctls
crypto: ccp: Add the SNP_SET_CONFIG command
crypto: ccp: Add the SNP_COMMIT command
crypto: ccp: Add the SNP_PLATFORM_STATUS command
x86/cpufeatures: Enable/unmask SEV-SNP CPU feature
KVM: SEV: Make AVIC backing, VMSA and VMCB memory allocation SNP safe
crypto: ccp: Add panic notifier for SEV/SNP firmware shutdown on kdump
iommu/amd: Clean up RMP entries for IOMMU pages during SNP shutdown
crypto: ccp: Handle legacy SEV commands when SNP is enabled
crypto: ccp: Handle non-volatile INIT_EX data when SNP is enabled
crypto: ccp: Handle the legacy TMR allocation when SNP is enabled
x86/sev: Introduce an SNP leaked pages list
crypto: ccp: Provide an API to issue SEV and SNP commands
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 FRED support from Thomas Gleixner:
"Support for x86 Fast Return and Event Delivery (FRED).
FRED is a replacement for IDT event delivery on x86 and addresses most
of the technical nightmares which IDT exposes:
1) Exception cause registers like CR2 need to be manually preserved
in nested exception scenarios.
2) Hardware interrupt stack switching is suboptimal for nested
exceptions as the interrupt stack mechanism rewinds the stack on
each entry which requires a massive effort in the low level entry
of #NMI code to handle this.
3) No hardware distinction between entry from kernel or from user
which makes establishing kernel context more complex than it needs
to be especially for unconditionally nestable exceptions like NMI.
4) NMI nesting caused by IRET unconditionally reenabling NMIs, which
is a problem when the perf NMI takes a fault when collecting a
stack trace.
5) Partial restore of ESP when returning to a 16-bit segment
6) Limitation of the vector space which can cause vector exhaustion
on large systems.
7) Inability to differentiate NMI sources
FRED addresses these shortcomings by:
1) An extended exception stack frame which the CPU uses to save
exception cause registers. This ensures that the meta information
for each exception is preserved on stack and avoids the extra
complexity of preserving it in software.
2) Hardware interrupt stack switching is non-rewinding if a nested
exception uses the currently interrupt stack.
3) The entry points for kernel and user context are separate and GS
BASE handling which is required to establish kernel context for
per CPU variable access is done in hardware.
4) NMIs are now nesting protected. They are only reenabled on the
return from NMI.
5) FRED guarantees full restore of ESP
6) FRED does not put a limitation on the vector space by design
because it uses a central entry points for kernel and user space
and the CPUstores the entry type (exception, trap, interrupt,
syscall) on the entry stack along with the vector number. The
entry code has to demultiplex this information, but this removes
the vector space restriction.
The first hardware implementations will still have the current
restricted vector space because lifting this limitation requires
further changes to the local APIC.
7) FRED stores the vector number and meta information on stack which
allows having more than one NMI vector in future hardware when the
required local APIC changes are in place.
The series implements the initial FRED support by:
- Reworking the existing entry and IDT handling infrastructure to
accomodate for the alternative entry mechanism.
- Expanding the stack frame to accomodate for the extra 16 bytes FRED
requires to store context and meta information
- Providing FRED specific C entry points for events which have
information pushed to the extended stack frame, e.g. #PF and #DB.
- Providing FRED specific C entry points for #NMI and #MCE
- Implementing the FRED specific ASM entry points and the C code to
demultiplex the events
- Providing detection and initialization mechanisms and the necessary
tweaks in context switching, GS BASE handling etc.
The FRED integration aims for maximum code reuse vs the existing IDT
implementation to the extent possible and the deviation in hot paths
like context switching are handled with alternatives to minimalize the
impact. The low level entry and exit paths are seperate due to the
extended stack frame and the hardware based GS BASE swichting and
therefore have no impact on IDT based systems.
It has been extensively tested on existing systems and on the FRED
simulation and as of now there are no outstanding problems"
* tag 'x86-fred-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (38 commits)
x86/fred: Fix init_task thread stack pointer initialization
MAINTAINERS: Add a maintainer entry for FRED
x86/fred: Fix a build warning with allmodconfig due to 'inline' failing to inline properly
x86/fred: Invoke FRED initialization code to enable FRED
x86/fred: Add FRED initialization functions
x86/syscall: Split IDT syscall setup code into idt_syscall_init()
KVM: VMX: Call fred_entry_from_kvm() for IRQ/NMI handling
x86/entry: Add fred_entry_from_kvm() for VMX to handle IRQ/NMI
x86/entry/calling: Allow PUSH_AND_CLEAR_REGS being used beyond actual entry code
x86/fred: Fixup fault on ERETU by jumping to fred_entrypoint_user
x86/fred: Let ret_from_fork_asm() jmp to asm_fred_exit_user when FRED is enabled
x86/traps: Add sysvec_install() to install a system interrupt handler
x86/fred: FRED entry/exit and dispatch code
x86/fred: Add a machine check entry stub for FRED
x86/fred: Add a NMI entry stub for FRED
x86/fred: Add a debug fault entry stub for FRED
x86/idtentry: Incorporate definitions/declarations of the FRED entries
x86/fred: Make exc_page_fault() work for FRED
x86/fred: Allow single-step trap and NMI when starting a new task
x86/fred: No ESPFIX needed when FRED is enabled
...
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Mitigation for RFDS requires RFDS_CLEAR capability which is enumerated
by MSR_IA32_ARCH_CAPABILITIES bit 27. If the host has it set, export it
to guests so that they can deploy the mitigation.
RFDS_NO indicates that the system is not vulnerable to RFDS, export it
to guests so that they don't deploy the mitigation unnecessarily. When
the host is not affected by X86_BUG_RFDS, but has RFDS_NO=0, synthesize
RFDS_NO to the guest.
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
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KVM Xen and pfncache changes for 6.9:
- Rip out the half-baked support for using gfn_to_pfn caches to manage pages
that are "mapped" into guests via physical addresses.
- Add support for using gfn_to_pfn caches with only a host virtual address,
i.e. to bypass the "gfn" stage of the cache. The primary use case is
overlay pages, where the guest may change the gfn used to reference the
overlay page, but the backing hva+pfn remains the same.
- Add an ioctl() to allow mapping Xen's shared_info page using an hva instead
of a gpa, so that userspace doesn't need to reconfigure and invalidate the
cache/mapping if the guest changes the gpa (but userspace keeps the resolved
hva the same).
- When possible, use a single host TSC value when computing the deadline for
Xen timers in order to improve the accuracy of the timer emulation.
- Inject pending upcall events when the vCPU software-enables its APIC to fix
a bug where an upcall can be lost (and to follow Xen's behavior).
- Fall back to the slow path instead of warning if "fast" IRQ delivery of Xen
events fails, e.g. if the guest has aliased xAPIC IDs.
- Extend gfn_to_pfn_cache's mutex to cover (de)activation (in addition to
refresh), and drop a now-redundant acquisition of xen_lock (that was
protecting the shared_info cache) to fix a deadlock due to recursively
acquiring xen_lock.
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KVM x86 PMU changes for 6.9:
- Fix several bugs where KVM speciously prevents the guest from utilizing
fixed counters and architectural event encodings based on whether or not
guest CPUID reports support for the _architectural_ encoding.
- Fix a variety of bugs in KVM's emulation of RDPMC, e.g. for "fast" reads,
priority of VMX interception vs #GP, PMC types in architectural PMUs, etc.
- Add a selftest to verify KVM correctly emulates RDMPC, counter availability,
and a variety of other PMC-related behaviors that depend on guest CPUID,
i.e. are difficult to validate via KVM-Unit-Tests.
- Zero out PMU metadata on AMD if the virtual PMU is disabled to avoid wasting
cycles, e.g. when checking if a PMC event needs to be synthesized when
skipping an instruction.
- Optimize triggering of emulated events, e.g. for "count instructions" events
when skipping an instruction, which yields a ~10% performance improvement in
VM-Exit microbenchmarks when a vPMU is exposed to the guest.
- Tighten the check for "PMI in guest" to reduce false positives if an NMI
arrives in the host while KVM is handling an IRQ VM-Exit.
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KVM VMX changes for 6.9:
- Fix a bug where KVM would report stale/bogus exit qualification information
when exiting to userspace due to an unexpected VM-Exit while the CPU was
vectoring an exception.
- Add a VMX flag in /proc/cpuinfo to report 5-level EPT support.
- Clean up the logic for massaging the passthrough MSR bitmaps when userspace
changes its MSR filter.
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KVM x86 MMU changes for 6.9:
- Clean up code related to unprotecting shadow pages when retrying a guest
instruction after failed #PF-induced emulation.
- Zap TDP MMU roots at 4KiB granularity to minimize the delay in yielding if
a reschedule is needed, e.g. if a high priority task needs to run. Because
KVM doesn't support yielding in the middle of processing a zapped non-leaf
SPTE, zapping at 1GiB granularity can result in multi-millisecond lag when
attempting to schedule in a high priority.
- Rework TDP MMU root unload, free, and alloc to run with mmu_lock held for
read, e.g. to avoid serializing vCPUs when userspace deletes a memslot.
- Allocate write-tracking metadata on-demand to avoid the memory overhead when
running kernels built with KVMGT support (external write-tracking enabled),
but for workloads that don't use nested virtualization (shadow paging) or
KVMGT.
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KVM x86 misc changes for 6.9:
- Explicitly initialize a variety of on-stack variables in the emulator that
triggered KMSAN false positives (though in fairness in KMSAN, it's comically
difficult to see that the uninitialized memory is never truly consumed).
- Fix the deubgregs ABI for 32-bit KVM, and clean up code related to reading
DR6 and DR7.
- Rework the "force immediate exit" code so that vendor code ultimately
decides how and when to force the exit. This allows VMX to further optimize
handling preemption timer exits, and allows SVM to avoid sending a duplicate
IPI (SVM also has a need to force an exit).
- Fix a long-standing bug where kvm_has_noapic_vcpu could be left elevated if
vCPU creation ultimately failed, and add WARN to guard against similar bugs.
- Provide a dedicated arch hook for checking if a different vCPU was in-kernel
(for directed yield), and simplify the logic for checking if the currently
loaded vCPU is in-kernel.
- Misc cleanups and fixes.
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https://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD
KVM/arm64 updates for 6.9
- Infrastructure for building KVM's trap configuration based on the
architectural features (or lack thereof) advertised in the VM's ID
registers
- Support for mapping vfio-pci BARs as Normal-NC (vaguely similar to
x86's WC) at stage-2, improving the performance of interacting with
assigned devices that can tolerate it
- Conversion of KVM's representation of LPIs to an xarray, utilized to
address serialization some of the serialization on the LPI injection
path
- Support for _architectural_ VHE-only systems, advertised through the
absence of FEAT_E2H0 in the CPU's ID register
- Miscellaneous cleanups, fixes, and spelling corrections to KVM and
selftests
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git://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson into HEAD
LoongArch KVM changes for v6.9
* Set reserved bits as zero in CPUCFG.
* Start SW timer only when vcpu is blocking.
* Do not restart SW timer when it is expired.
* Remove unnecessary CSR register saving during enter guest.
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Pull kvm fixes from Paolo Bonzini:
"KVM GUEST_MEMFD fixes for 6.8:
- Make KVM_MEM_GUEST_MEMFD mutually exclusive with KVM_MEM_READONLY
to avoid creating an inconsistent ABI (KVM_MEM_GUEST_MEMFD is not
writable from userspace, so there would be no way to write to a
read-only guest_memfd).
- Update documentation for KVM_SW_PROTECTED_VM to make it abundantly
clear that such VMs are purely for development and testing.
- Limit KVM_SW_PROTECTED_VM guests to the TDP MMU, as the long term
plan is to support confidential VMs with deterministic private
memory (SNP and TDX) only in the TDP MMU.
- Fix a bug in a GUEST_MEMFD dirty logging test that caused false
passes.
x86 fixes:
- Fix missing marking of a guest page as dirty when emulating an
atomic access.
- Check for mmu_notifier invalidation events before faulting in the
pfn, and before acquiring mmu_lock, to avoid unnecessary work and
lock contention with preemptible kernels (including
CONFIG_PREEMPT_DYNAMIC in non-preemptible mode).
- Disable AMD DebugSwap by default, it breaks VMSA signing and will
be re-enabled with a better VM creation API in 6.10.
- Do the cache flush of converted pages in svm_register_enc_region()
before dropping kvm->lock, to avoid a race with unregistering of
the same region and the consequent use-after-free issue"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
SEV: disable SEV-ES DebugSwap by default
KVM: x86/mmu: Retry fault before acquiring mmu_lock if mapping is changing
KVM: SVM: Flush pages under kvm->lock to fix UAF in svm_register_enc_region()
KVM: selftests: Add a testcase to verify GUEST_MEMFD and READONLY are exclusive
KVM: selftests: Create GUEST_MEMFD for relevant invalid flags testcases
KVM: x86/mmu: Restrict KVM_SW_PROTECTED_VM to the TDP MMU
KVM: x86: Update KVM_SW_PROTECTED_VM docs to make it clear they're a WIP
KVM: Make KVM_MEM_GUEST_MEMFD mutually exclusive with KVM_MEM_READONLY
KVM: x86: Mark target gfn of emulated atomic instruction as dirty
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https://github.com/kvm-x86/linux into HEAD
KVM GUEST_MEMFD fixes for 6.8:
- Make KVM_MEM_GUEST_MEMFD mutually exclusive with KVM_MEM_READONLY to
avoid creating ABI that KVM can't sanely support.
- Update documentation for KVM_SW_PROTECTED_VM to make it abundantly
clear that such VMs are purely a development and testing vehicle, and
come with zero guarantees.
- Limit KVM_SW_PROTECTED_VM guests to the TDP MMU, as the long term plan
is to support confidential VMs with deterministic private memory (SNP
and TDX) only in the TDP MMU.
- Fix a bug in a GUEST_MEMFD negative test that resulted in false passes
when verifying that KVM_MEM_GUEST_MEMFD memslots can't be dirty logged.
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The DebugSwap feature of SEV-ES provides a way for confidential guests to use
data breakpoints. However, because the status of the DebugSwap feature is
recorded in the VMSA, enabling it by default invalidates the attestation
signatures. In 6.10 we will introduce a new API to create SEV VMs that
will allow enabling DebugSwap based on what the user tells KVM to do.
Contextually, we will change the legacy KVM_SEV_ES_INIT API to never
enable DebugSwap.
For compatibility with kernels that pre-date the introduction of DebugSwap,
as well as with those where KVM_SEV_ES_INIT will never enable it, do not enable
the feature by default. If anybody wants to use it, for now they can enable
the sev_es_debug_swap_enabled module parameter, but this will result in a
warning.
Fixes: d1f85fbe836e ("KVM: SEV: Enable data breakpoints in SEV-ES")
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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https://github.com/kvm-x86/linux into HEAD
KVM GUEST_MEMFD fixes for 6.8:
- Make KVM_MEM_GUEST_MEMFD mutually exclusive with KVM_MEM_READONLY to
avoid creating ABI that KVM can't sanely support.
- Update documentation for KVM_SW_PROTECTED_VM to make it abundantly
clear that such VMs are purely a development and testing vehicle, and
come with zero guarantees.
- Limit KVM_SW_PROTECTED_VM guests to the TDP MMU, as the long term plan
is to support confidential VMs with deterministic private memory (SNP
and TDX) only in the TDP MMU.
- Fix a bug in a GUEST_MEMFD negative test that resulted in false passes
when verifying that KVM_MEM_GUEST_MEMFD memslots can't be dirty logged.
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KVM x86 fixes for 6.8, round 2:
- When emulating an atomic access, mark the gfn as dirty in the memslot
to fix a bug where KVM could fail to mark the slot as dirty during live
migration, ultimately resulting in guest data corruption due to a dirty
page not being re-copied from the source to the target.
- Check for mmu_notifier invalidation events before faulting in the pfn,
and before acquiring mmu_lock, to avoid unnecessary work and lock
contention. Contending mmu_lock is especially problematic on preemptible
kernels, as KVM may yield mmu_lock in response to the contention, which
severely degrades overall performance due to vCPUs making it difficult
for the task that triggered invalidation to make forward progress.
Note, due to another kernel bug, this fix isn't limited to preemtible
kernels, as any kernel built with CONFIG_PREEMPT_DYNAMIC=y will yield
contended rwlocks and spinlocks.
https://lore.kernel.org/all/20240110214723.695930-1-seanjc@google.com
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They're not used anymore, drop all of them.
Link: https://lkml.kernel.org/r/20240305043750.93762-10-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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pud_large() is always defined as pud_leaf(). Merge their usages. Chose
pud_leaf() because pud_leaf() is a global API, while pud_large() is not.
Link: https://lkml.kernel.org/r/20240305043750.93762-9-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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pmd_large() is always defined as pmd_leaf(). Merge their usages. Chose
pmd_leaf() because pmd_leaf() is a global API, while pmd_large() is not.
Link: https://lkml.kernel.org/r/20240305043750.93762-8-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Commit ee3a5f9e3d9b ("KVM: x86: Do runtime CPUID update before updating
vcpu->arch.cpuid_entries") moved tweaking of the supplied CPUID
data earlier in kvm_set_cpuid() but __kvm_update_cpuid_runtime() actually
uses 'vcpu->arch.kvm_cpuid' (though __kvm_find_kvm_cpuid_features()) which
gets set later in kvm_set_cpuid(). In some cases, e.g. when kvm_set_cpuid()
is called for the first time and 'vcpu->arch.kvm_cpuid' is clear,
__kvm_find_kvm_cpuid_features() fails to find KVM PV feature entry and the
logic which clears KVM_FEATURE_PV_UNHALT after enabling
KVM_X86_DISABLE_EXITS_HLT does not work.
The logic, introduced by the commit ee3a5f9e3d9b ("KVM: x86: Do runtime
CPUID update before updating vcpu->arch.cpuid_entries") must stay: the
supplied CPUID data is tweaked by KVM first (__kvm_update_cpuid_runtime())
and checked later (kvm_check_cpuid()) and the actual data
(vcpu->arch.cpuid_*, vcpu->arch.kvm_cpuid, vcpu->arch.xen.cpuid,..) is only
updated on success.
Switch to searching for KVM_SIGNATURE in the supplied CPUID data to
discover KVM PV feature entry instead of using stale 'vcpu->arch.kvm_cpuid'.
While on it, drop pointless "&& (best->eax & (1 << KVM_FEATURE_PV_UNHALT)"
check when clearing KVM_FEATURE_PV_UNHALT bit.
Fixes: ee3a5f9e3d9b ("KVM: x86: Do runtime CPUID update before updating vcpu->arch.cpuid_entries")
Reported-and-tested-by: Li RongQing <lirongqing@baidu.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lore.kernel.org/r/20240228101837.93642-3-vkuznets@redhat.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Similar to kvm_find_kvm_cpuid_features()/__kvm_find_kvm_cpuid_features(),
introduce a helper to search for the specific hypervisor signature in any
struct kvm_cpuid_entry2 array, not only in vcpu->arch.cpuid_entries.
No functional change intended.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lore.kernel.org/r/20240228101837.93642-2-vkuznets@redhat.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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The fast-path timer delivery introduced a recursive locking deadlock
when userspace configures a timer which has already expired and is
delivered immediately. The call to kvm_xen_inject_timer_irqs() can
call to kvm_xen_set_evtchn() which may take kvm->arch.xen.xen_lock,
which is already held in kvm_xen_vcpu_get_attr().
============================================
WARNING: possible recursive locking detected
6.8.0-smp--5e10b4d51d77-drs #232 Tainted: G O
--------------------------------------------
xen_shinfo_test/250013 is trying to acquire lock:
ffff938c9930cc30 (&kvm->arch.xen.xen_lock){+.+.}-{3:3}, at: kvm_xen_set_evtchn+0x74/0x170 [kvm]
but task is already holding lock:
ffff938c9930cc30 (&kvm->arch.xen.xen_lock){+.+.}-{3:3}, at: kvm_xen_vcpu_get_attr+0x38/0x250 [kvm]
Now that the gfn_to_pfn_cache has its own self-sufficient locking, its
callers no longer need to ensure serialization, so just stop taking
kvm->arch.xen.xen_lock from kvm_xen_set_evtchn().
Fixes: 77c9b9dea4fb ("KVM: x86/xen: Use fast path for Xen timer delivery")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
Link: https://lore.kernel.org/r/20240227115648.3104-6-dwmw2@infradead.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
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The kvm_xen_inject_vcpu_vector() function has a comment saying "the fast
version will always work for physical unicast", justifying its use of
kvm_irq_delivery_to_apic_fast() and the WARN_ON_ONCE() when that fails.
In fact that assumption isn't true if X2APIC isn't in use by the guest
and there is (8-bit x)APIC ID aliasing. A single "unicast" destination
APIC ID *may* then be delivered to multiple vCPUs. Remove the warning,
and in fact it might as well just call kvm_irq_delivery_to_apic().
Reported-by: Michal Luczaj <mhal@rbox.co>
Fixes: fde0451be8fb3 ("KVM: x86/xen: Support per-vCPU event channel upcall via local APIC")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
Link: https://lore.kernel.org/r/20240227115648.3104-4-dwmw2@infradead.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Linux guests since commit b1c3497e604d ("x86/xen: Add support for
HVMOP_set_evtchn_upcall_vector") in v6.0 onwards will use the per-vCPU
upcall vector when it's advertised in the Xen CPUID leaves.
This upcall is injected through the guest's local APIC as an MSI, unlike
the older system vector which was merely injected by the hypervisor any
time the CPU was able to receive an interrupt and the upcall_pending
flags is set in its vcpu_info.
Effectively, that makes the per-CPU upcall edge triggered instead of
level triggered, which results in the upcall being lost if the MSI is
delivered when the local APIC is *disabled*.
Xen checks the vcpu_info->evtchn_upcall_pending flag when the local APIC
for a vCPU is software enabled (in fact, on any write to the SPIV
register which doesn't disable the APIC). Do the same in KVM since KVM
doesn't provide a way for userspace to intervene and trap accesses to
the SPIV register of a local APIC emulated by KVM.
Fixes: fde0451be8fb3 ("KVM: x86/xen: Support per-vCPU event channel upcall via local APIC")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240227115648.3104-3-dwmw2@infradead.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
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A test program such as http://david.woodhou.se/timerlat.c confirms user
reports that timers are increasingly inaccurate as the lifetime of a
guest increases. Reporting the actual delay observed when asking for
100µs of sleep, it starts off OK on a newly-launched guest but gets
worse over time, giving incorrect sleep times:
root@ip-10-0-193-21:~# ./timerlat -c -n 5
00000000 latency 103243/100000 (3.2430%)
00000001 latency 103243/100000 (3.2430%)
00000002 latency 103242/100000 (3.2420%)
00000003 latency 103245/100000 (3.2450%)
00000004 latency 103245/100000 (3.2450%)
The biggest problem is that get_kvmclock_ns() returns inaccurate values
when the guest TSC is scaled. The guest sees a TSC value scaled from the
host TSC by a mul/shift conversion (hopefully done in hardware). The
guest then converts that guest TSC value into nanoseconds using the
mul/shift conversion given to it by the KVM pvclock information.
But get_kvmclock_ns() performs only a single conversion directly from
host TSC to nanoseconds, giving a different result. A test program at
http://david.woodhou.se/tsdrift.c demonstrates the cumulative error
over a day.
It's non-trivial to fix get_kvmclock_ns(), although I'll come back to
that. The actual guest hv_clock is per-CPU, and *theoretically* each
vCPU could be running at a *different* frequency. But this patch is
needed anyway because...
The other issue with Xen timers was that the code would snapshot the
host CLOCK_MONOTONIC at some point in time, and then... after a few
interrupts may have occurred, some preemption perhaps... would also read
the guest's kvmclock. Then it would proceed under the false assumption
that those two happened at the *same* time. Any time which *actually*
elapsed between reading the two clocks was introduced as inaccuracies
in the time at which the timer fired.
Fix it to use a variant of kvm_get_time_and_clockread(), which reads the
host TSC just *once*, then use the returned TSC value to calculate the
kvmclock (making sure to do that the way the guest would instead of
making the same mistake get_kvmclock_ns() does).
Sadly, hrtimers based on CLOCK_MONOTONIC_RAW are not supported, so Xen
timers still have to use CLOCK_MONOTONIC. In practice the difference
between the two won't matter over the timescales involved, as the
*absolute* values don't matter; just the delta.
This does mean a new variant of kvm_get_time_and_clockread() is needed;
called kvm_get_monotonic_and_clockread() because that's what it does.
Fixes: 536395260582 ("KVM: x86/xen: handle PV timers oneshot mode")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
Link: https://lore.kernel.org/r/20240227115648.3104-2-dwmw2@infradead.org
[sean: massage moved comment, tweak if statement formatting]
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Sparse complains rightfully about the missing declaration which has been
placed sloppily into the usage site:
bugs.c:2223:6: sparse: warning: symbol 'itlb_multihit_kvm_mitigation' was not declared. Should it be static?
Add it to <asm/spec-ctrl.h> where it belongs and remove the one in the KVM code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20240304005104.787173239@linutronix.de
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Combine possible_passthrough_msr_slot() and is_valid_passthrough_msr()
into a single function, vmx_get_passthrough_msr_slot(), and have the
combined helper return the slot on success, using a negative value to
indicate "failure".
Combining the operations avoids iterating over the array of passthrough
MSRs twice for relevant MSRs.
Suggested-by: Dongli Zhang <dongli.zhang@oracle.com>
Reviewed-by: Dongli Zhang <dongli.zhang@oracle.com>
Link: https://lore.kernel.org/r/20240223202104.3330974-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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The write-track is used externally only by the gpu/drm/i915 driver.
Currently, it is always enabled, if a kernel has been compiled with this
driver.
Enabling the write-track mechanism adds a two-byte overhead per page across
all memory slots. It isn't significant for regular VMs. However in gVisor,
where the entire process virtual address space is mapped into the VM, even
with a 39-bit address space, the overhead amounts to 256MB.
Rework the write-tracking mechanism to enable it on-demand in
kvm_page_track_register_notifier.
Here is Sean's comment about the locking scheme:
The only potential hiccup would be if taking slots_arch_lock would
deadlock, but it should be impossible for slots_arch_lock to be taken in
any other path that involves VFIO and/or KVMGT *and* can be coincident.
Except for kvm_arch_destroy_vm() (which deletes KVM's internal
memslots), slots_arch_lock is taken only through KVM ioctls(), and the
caller of kvm_page_track_register_notifier() *must* hold a reference to
the VM.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Andrei Vagin <avagin@google.com>
Link: https://lore.kernel.org/r/20240213192340.2023366-1-avagin@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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The vmx_msr_filter_changed() may directly/indirectly calls only
vmx_enable_intercept_for_msr() or vmx_disable_intercept_for_msr(). Those
two functions may exit immediately if !cpu_has_vmx_msr_bitmap().
vmx_msr_filter_changed()
-> vmx_disable_intercept_for_msr()
-> pt_update_intercept_for_msr()
-> vmx_set_intercept_for_msr()
-> vmx_enable_intercept_for_msr()
-> vmx_disable_intercept_for_msr()
Therefore, we exit early if !cpu_has_vmx_msr_bitmap().
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Link: https://lore.kernel.org/r/20240223202104.3330974-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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According to the is_valid_passthrough_msr(), the LBR MSRs are also
passthrough MSRs, since the commit 1b5ac3226a1a ("KVM: vmx/pmu:
Pass-through LBR msrs when the guest LBR event is ACTIVE").
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Link: https://lore.kernel.org/r/20240223202104.3330974-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Explicitly check that the source of external interrupt is indeed an NMI
in kvm_arch_pmi_in_guest(), which reduces perf-kvm false positive samples
(host samples labelled as guest samples) generated by perf/core NMI mode
if an NMI arrives after VM-Exit, but before kvm_after_interrupt():
# test: perf-record + cpu-cycles:HP (which collects host-only precise samples)
# Symbol Overhead sys usr guest sys guest usr
# ....................................... ........ ........ ........ ......... .........
#
# Before:
[g] entry_SYSCALL_64 24.63% 0.00% 0.00% 24.63% 0.00%
[g] syscall_return_via_sysret 23.23% 0.00% 0.00% 23.23% 0.00%
[g] files_lookup_fd_raw 6.35% 0.00% 0.00% 6.35% 0.00%
# After:
[k] perf_adjust_freq_unthr_context 57.23% 57.23% 0.00% 0.00% 0.00%
[k] __vmx_vcpu_run 4.09% 4.09% 0.00% 0.00% 0.00%
[k] vmx_update_host_rsp 3.17% 3.17% 0.00% 0.00% 0.00%
In the above case, perf records the samples labelled '[g]', the RIPs behind
the weird samples are actually being queried by perf_instruction_pointer()
after determining whether it's in GUEST state or not, and here's the issue:
If VM-Exit is caused by a non-NMI interrupt (such as hrtimer_interrupt) and
at least one PMU counter is enabled on host, the kvm_arch_pmi_in_guest()
will remain true (KVM_HANDLING_IRQ is set) until kvm_before_interrupt().
During this window, if a PMI occurs on host (since the KVM instructions on
host are being executed), the control flow, with the help of the host NMI
context, will be transferred to perf/core to generate performance samples,
thus perf_instruction_pointer() and perf_guest_get_ip() is called.
Since kvm_arch_pmi_in_guest() only checks if there is an interrupt, it may
cause perf/core to mistakenly assume that the source RIP of the host NMI
belongs to the guest world and use perf_guest_get_ip() to get the RIP of
a vCPU that has already exited by a non-NMI interrupt.
Error samples are recorded and presented to the end-user via perf-report.
Such false positive samples could be eliminated by explicitly determining
if the exit reason is KVM_HANDLING_NMI.
Note that when VM-exit is indeed triggered by PMI and before HANDLING_NMI
is cleared, it's also still possible that another PMI is generated on host.
Also for perf/core timer mode, the false positives are still possible since
those non-NMI sources of interrupts are not always being used by perf/core.
For events that are host-only, perf/core can and should eliminate false
positives by checking event->attr.exclude_guest, i.e. events that are
configured to exclude KVM guests should never fire in the guest.
Events that are configured to count host and guest are trickier, perhaps
impossible to handle with 100% accuracy? And regardless of what accuracy
is provided by perf/core, improving KVM's accuracy is cheap and easy, with
no real downsides.
Fixes: dd60d217062f ("KVM: x86: Fix perf timer mode IP reporting")
Signed-off-by: Like Xu <likexu@tencent.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20231206032054.55070-1-likexu@tencent.com
[sean: massage changelog, squash !!in_nmi() fixup from Like]
Signed-off-by: Sean Christopherson <seanjc@google.com>
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The general expectation with debugfs is that any initialization failure
is nonfatal. Nevertheless, kvm_arch_create_vm_debugfs() allows
implementations to return an error and kvm_create_vm_debugfs() allows
that to fail VM creation.
Change to a void return to discourage architectures from making debugfs
failures fatal for the VM. Seems like everyone already had the right
idea, as all implementations already return 0 unconditionally.
Acked-by: Marc Zyngier <maz@kernel.org>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20240216155941.2029458-1-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
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Retry page faults without acquiring mmu_lock, and without even faulting
the page into the primary MMU, if the resolved gfn is covered by an active
invalidation. Contending for mmu_lock is especially problematic on
preemptible kernels as the mmu_notifier invalidation task will yield
mmu_lock (see rwlock_needbreak()), delay the in-progress invalidation, and
ultimately increase the latency of resolving the page fault. And in the
worst case scenario, yielding will be accompanied by a remote TLB flush,
e.g. if the invalidation covers a large range of memory and vCPUs are
accessing addresses that were already zapped.
Faulting the page into the primary MMU is similarly problematic, as doing
so may acquire locks that need to be taken for the invalidation to
complete (the primary MMU has finer grained locks than KVM's MMU), and/or
may cause unnecessary churn (getting/putting pages, marking them accessed,
etc).
Alternatively, the yielding issue could be mitigated by teaching KVM's MMU
iterators to perform more work before yielding, but that wouldn't solve
the lock contention and would negatively affect scenarios where a vCPU is
trying to fault in an address that is NOT covered by the in-progress
invalidation.
Add a dedicated lockess version of the range-based retry check to avoid
false positives on the sanity check on start+end WARN, and so that it's
super obvious that checking for a racing invalidation without holding
mmu_lock is unsafe (though obviously useful).
Wrap mmu_invalidate_in_progress in READ_ONCE() to ensure that pre-checking
invalidation in a loop won't put KVM into an infinite loop, e.g. due to
caching the in-progress flag and never seeing it go to '0'.
Force a load of mmu_invalidate_seq as well, even though it isn't strictly
necessary to avoid an infinite loop, as doing so improves the probability
that KVM will detect an invalidation that already completed before
acquiring mmu_lock and bailing anyways.
Do the pre-check even for non-preemptible kernels, as waiting to detect
the invalidation until mmu_lock is held guarantees the vCPU will observe
the worst case latency in terms of handling the fault, and can generate
even more mmu_lock contention. E.g. the vCPU will acquire mmu_lock,
detect retry, drop mmu_lock, re-enter the guest, retake the fault, and
eventually re-acquire mmu_lock. This behavior is also why there are no
new starvation issues due to losing the fairness guarantees provided by
rwlocks: if the vCPU needs to retry, it _must_ drop mmu_lock, i.e. waiting
on mmu_lock doesn't guarantee forward progress in the face of _another_
mmu_notifier invalidation event.
Note, adding READ_ONCE() isn't entirely free, e.g. on x86, the READ_ONCE()
may generate a load into a register instead of doing a direct comparison
(MOV+TEST+Jcc instead of CMP+Jcc), but practically speaking the added cost
is a few bytes of code and maaaaybe a cycle or three.
Reported-by: Yan Zhao <yan.y.zhao@intel.com>
Closes: https://lore.kernel.org/all/ZNnPF4W26ZbAyGto@yzhao56-desk.sh.intel.com
Reported-by: Friedrich Weber <f.weber@proxmox.com>
Cc: Kai Huang <kai.huang@intel.com>
Cc: Yan Zhao <yan.y.zhao@intel.com>
Cc: Yuan Yao <yuan.yao@linux.intel.com>
Cc: Xu Yilun <yilun.xu@linux.intel.com>
Acked-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Yan Zhao <yan.y.zhao@intel.com>
Link: https://lore.kernel.org/r/20240222012640.2820927-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Commit 54b8ae66ae1a ("kbuild: change *FLAGS_<basetarget>.o to take the
path relative to $(obj)") changed the syntax of per-file compiler flags.
The situation is the same for the following variables:
OBJECT_FILES_NON_STANDARD_<basetarget>.o
GCOV_PROFILE_<basetarget>.o
KASAN_SANITIZE_<basetarget>.o
KMSAN_SANITIZE_<basetarget>.o
KMSAN_ENABLE_CHECKS_<basetarget>.o
UBSAN_SANITIZE_<basetarget>.o
KCOV_INSTRUMENT_<basetarget>.o
KCSAN_SANITIZE_<basetarget>.o
KCSAN_INSTRUMENT_BARRIERS_<basetarget>.o
The <basetarget> is the filename of the target with its directory and
suffix stripped.
This syntax comes into a trouble when two files with the same basename
appear in one Makefile, for example:
obj-y += dir1/foo.o
obj-y += dir2/foo.o
OBJECT_FILES_NON_STANDARD_foo.o := y
OBJECT_FILES_NON_STANDARD_foo.o is applied to both dir1/foo.o and
dir2/foo.o. This syntax is not flexbile enough to handle cases where
one of them is a standard object, but the other is not.
It is more sensible to use the relative path to the Makefile, like this:
obj-y += dir1/foo.o
OBJECT_FILES_NON_STANDARD_dir1/foo.o := y
obj-y += dir2/foo.o
OBJECT_FILES_NON_STANDARD_dir2/foo.o := y
To maintain the current behavior, I made adjustments to the following two
Makefiles:
- arch/x86/entry/vdso/Makefile, which compiles vclock_gettime.o, vgetcpu.o,
and their vdso32 variants.
- arch/x86/kvm/Makefile, which compiles vmx/vmenter.o and svm/vmenter.o
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Acked-by: Sean Christopherson <seanjc@google.com>
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Do the cache flush of converted pages in svm_register_enc_region() before
dropping kvm->lock to fix use-after-free issues where region and/or its
array of pages could be freed by a different task, e.g. if userspace has
__unregister_enc_region_locked() already queued up for the region.
Note, the "obvious" alternative of using local variables doesn't fully
resolve the bug, as region->pages is also dynamically allocated. I.e. the
region structure itself would be fine, but region->pages could be freed.
Flushing multiple pages under kvm->lock is unfortunate, but the entire
flow is a rare slow path, and the manual flush is only needed on CPUs that
lack coherency for encrypted memory.
Fixes: 19a23da53932 ("Fix unsynchronized access to sev members through svm_register_enc_region")
Reported-by: Gabe Kirkpatrick <gkirkpatrick@google.com>
Cc: Josh Eads <josheads@google.com>
Cc: Peter Gonda <pgonda@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20240217013430.2079561-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Advertise and support software-protected VMs if and only if the TDP MMU is
enabled, i.e. disallow KVM_SW_PROTECTED_VM if TDP is enabled for KVM's
legacy/shadow MMU. TDP support for the shadow MMU is maintenance-only,
e.g. support for TDX and SNP will also be restricted to the TDP MMU.
Fixes: 89ea60c2c7b5 ("KVM: x86: Add support for "protected VMs" that can utilize private memory")
Link: https://lore.kernel.org/r/20240222190612.2942589-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Rewrite the help message for KVM_SW_PROTECTED_VM to make it clear that
software-protected VMs are a development and testing vehicle for
guest_memfd(), and that attempting to use KVM_SW_PROTECTED_VM for anything
remotely resembling a "real" VM will fail. E.g. any memory accesses from
KVM will incorrectly access shared memory, nested TDP is wildly broken,
and so on and so forth.
Update KVM's API documentation with similar warnings to discourage anyone
from attempting to run anything but selftests with KVM_X86_SW_PROTECTED_VM.
Fixes: 89ea60c2c7b5 ("KVM: x86: Add support for "protected VMs" that can utilize private memory")
Link: https://lore.kernel.org/r/20240222190612.2942589-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Free TDP MMU roots from vCPU context while holding mmu_lock for read, it
is completely legal to invoke kvm_tdp_mmu_put_root() as a reader. This
eliminates the last mmu_lock writer in the TDP MMU's "fast zap" path
after requesting vCPUs to reload roots, i.e. allows KVM to zap invalidated
roots, free obsolete roots, and allocate new roots in parallel.
On large VMs, e.g. 100+ vCPUs, allowing the bulk of the "fast zap"
operation to run in parallel with freeing and allocating roots reduces the
worst case latency for a vCPU to reload a root from 2-3ms to <100us.
Link: https://lore.kernel.org/r/20240111020048.844847-9-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Allocate TDP MMU roots while holding mmu_lock for read, and instead use
tdp_mmu_pages_lock to guard against duplicate roots. This allows KVM to
create new roots without forcing kvm_tdp_mmu_zap_invalidated_roots() to
yield, e.g. allows vCPUs to load new roots after memslot deletion without
forcing the zap thread to detect contention and yield (or complete if the
kernel isn't preemptible).
Note, creating a new TDP MMU root as an mmu_lock reader is safe for two
reasons: (1) paths that must guarantee all roots/SPTEs are *visited* take
mmu_lock for write and so are still mutually exclusive, e.g. mmu_notifier
invalidations, and (2) paths that require all roots/SPTEs to *observe*
some given state without holding mmu_lock for write must ensure freshness
through some other means, e.g. toggling dirty logging must first wait for
SRCU readers to recognize the memslot flags change before processing
existing roots/SPTEs.
Link: https://lore.kernel.org/r/20240111020048.844847-8-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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When allocating a new TDP MMU root, check for a usable root while holding
mmu_lock for read and only acquire mmu_lock for write if a new root needs
to be created. There is no need to serialize other MMU operations if a
vCPU is simply grabbing a reference to an existing root, holding mmu_lock
for write is "necessary" (spoiler alert, it's not strictly necessary) only
to ensure KVM doesn't end up with duplicate roots.
Allowing vCPUs to get "new" roots in parallel is beneficial to VM boot and
to setups that frequently delete memslots, i.e. which force all vCPUs to
reload all roots.
Link: https://lore.kernel.org/r/20240111020048.844847-7-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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When write-protecting SPTEs, don't process invalid roots as invalid roots
are unreachable, i.e. can't be used to access guest memory and thus don't
need to be write-protected.
Note, this is *almost* a nop for kvm_tdp_mmu_clear_dirty_pt_masked(),
which is called under slots_lock, i.e. is mutually exclusive with
kvm_mmu_zap_all_fast(). But it's possible for something other than the
"fast zap" thread to grab a reference to an invalid root and thus keep a
root alive (but completely empty) after kvm_mmu_zap_all_fast() completes.
The kvm_tdp_mmu_write_protect_gfn() case is more interesting as KVM write-
protects SPTEs for reasons other than dirty logging, e.g. if a KVM creates
a SPTE for a nested VM while a fast zap is in-progress.
Add another TDP MMU iterator to visit only valid roots, and
opportunistically convert kvm_tdp_mmu_get_vcpu_root_hpa() to said iterator.
Link: https://lore.kernel.org/r/20240111020048.844847-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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When zapping a GFN in response to an APICv or MTRR change, don't zap SPTEs
for invalid roots as KVM only needs to ensure the guest can't use stale
mappings for the GFN. Unlike kvm_tdp_mmu_unmap_gfn_range(), which must
zap "unreachable" SPTEs to ensure KVM doesn't mark a page accessed/dirty,
kvm_tdp_mmu_zap_leafs() isn't used (and isn't intended to be used) to
handle freeing of host memory.
Link: https://lore.kernel.org/r/20240111020048.844847-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Modify for_each_tdp_mmu_root() and __for_each_tdp_mmu_root_yield_safe() to
accept -1 for _as_id to mean "process all memslot address spaces". That
way code that wants to process both SMM and !SMM doesn't need to iterate
over roots twice (and likely copy+paste code in the process).
Deliberately don't cast _as_id to an "int", just in case not casting helps
the compiler elide the "_as_id >=0" check when being passed an unsigned
value, e.g. from a memslot.
No functional change intended.
Link: https://lore.kernel.org/r/20240111020048.844847-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Don't force a TLB flush when zapping SPTEs in invalid roots as vCPUs
can't be actively using invalid roots (zapping SPTEs in invalid roots is
necessary only to ensure KVM doesn't mark a page accessed/dirty after it
is freed by the primary MMU).
Link: https://lore.kernel.org/r/20240111020048.844847-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Zap invalidated TDP MMU roots at maximum granularity, i.e. with more
frequent conditional resched checkpoints, in order to avoid running for an
extended duration (milliseconds, or worse) without honoring a reschedule
request. And for kernels running with full or real-time preempt models,
zapping at 4KiB granularity also provides significantly reduced latency
for other tasks that are contending for mmu_lock (which isn't necessarily
an overall win for KVM, but KVM should do its best to honor the kernel's
preemption model).
To keep KVM's assertion that zapping at 1GiB granularity is functionally
ok, which is the main reason 1GiB was selected in the past, skip straight
to zapping at 1GiB if KVM is configured to prove the MMU. Zapping roots
is far more common than a vCPU replacing a 1GiB page table with a hugepage,
e.g. generally happens multiple times during boot, and so keeping the test
coverage provided by root zaps is desirable, just not for production.
Cc: David Matlack <dmatlack@google.com>
Cc: Pattara Teerapong <pteerapong@google.com>
Link: https://lore.kernel.org/r/20240111020048.844847-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Directly return the boolean result of whether or not a vCPU has a pending
interrupt instead of effectively doing:
if (true)
return true;
return false;
Reviewed-by: Yuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20240110003938.490206-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Snapshot preempted_in_kernel using kvm_arch_vcpu_in_kernel() so that the
flag is "accurate" (or rather, consistent and deterministic within KVM)
for guests with protected state, and explicitly use preempted_in_kernel
when checking if a vCPU was preempted in kernel mode instead of bouncing
through kvm_arch_vcpu_in_kernel().
Drop the gnarly logic in kvm_arch_vcpu_in_kernel() that redirects to
preempted_in_kernel if the target vCPU is not the "running", i.e. loaded,
vCPU, as the only reason that code existed was for the directed yield case
where KVM wants to check the CPL of a vCPU that may or may not be loaded
on the current pCPU.
Cc: Like Xu <like.xu.linux@gmail.com>
Reviewed-by: Yuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20240110003938.490206-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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