kernel/linux.git/arch/x86/include, branch v6.19.11

KVM: x86: Introduce KVM_X86_QUIRK_VMCS12_ALLOW_FREEZE_IN_SMM

2026-03-19T15:15:02+00:00

commit e2ffe85b6d2bb7780174b87aa4468a39be17eb81 upstream. Add KVM_X86_QUIRK_VMCS12_ALLOW_FREEZE_IN_SMM to allow L1 to set FREEZE_IN_SMM in vmcs12's GUEST_IA32_DEBUGCTL field, as permitted prior to commit 6b1dd26544d0 ("KVM: VMX: Preserve host's DEBUGCTLMSR_FREEZE_IN_SMM while running the guest"). Enable the quirk by default for backwards compatibility (like all quirks); userspace can disable it via KVM_CAP_DISABLE_QUIRKS2 for consistency with the constraints on WRMSR(IA32_DEBUGCTL). Note that the quirk only bypasses the consistency check. The vmcs02 bit is still owned by the host, and PMCs are not frozen during virtualized SMM. In particular, if a host administrator decides that PMCs should not be frozen during physical SMM, then L1 has no say in the matter. Fixes: 095686e6fcb4 ("KVM: nVMX: Check vmcs12->guest_ia32_debugctl on nested VM-Enter") Cc: stable@vger.kernel.org Signed-off-by: Jim Mattson Link: https://patch.msgid.link/20260205231537.1278753-1-jmattson@google.com [sean: tag for stable@, clean-up and fix goofs in the comment and docs] Signed-off-by: Sean Christopherson [Rename quirk. - Paolo] Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman

x86/topo: Add topology_num_nodes_per_package()

2026-03-12T11:09:55+00:00

[ Upstream commit ae6730ff42b3a13d94b405edeb5e40108b6d21b6 ] Use the MADT and SRAT table data to compute __num_nodes_per_package. Specifically, SRAT has already been parsed in x86_numa_init(), which is called before acpi_boot_init() which parses MADT. So both are available in topology_init_possible_cpus(). This number is useful to divinate the various Intel CoD/SNC and AMD NPS modes, since the platforms are failing to provide this otherwise. Doing it this way is independent of the number of online CPUs and other such shenanigans. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Ingo Molnar Tested-by: Tony Luck Tested-by: K Prateek Nayak Tested-by: Zhang Rui Tested-by: Chen Yu Tested-by: Kyle Meyer Link: https://patch.msgid.link/20260303110100.004091624@infradead.org Stable-dep-of: 528d89a4707e ("x86/topo: Fix SNC topology mess") Signed-off-by: Sasha Levin

x86/numa: Store extra copy of numa_nodes_parsed

2026-03-12T11:09:55+00:00

[ Upstream commit 48084cc153a5b0fbf0aa98d47670d3be0b9f64d5 ] The topology setup code needs to know the total number of physical nodes enumerated in SRAT; however NUMA_EMU can cause the existing numa_nodes_parsed bitmap to be fictitious. Therefore, keep a copy of the bitmap specifically to retain the physical node count. Suggested-by: K Prateek Nayak Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Ingo Molnar Tested-by: K Prateek Nayak Tested-by: Zhang Rui Tested-by: Chen Yu Tested-by: Kyle Meyer Link: https://patch.msgid.link/20260303110059.889884023@infradead.org Stable-dep-of: 528d89a4707e ("x86/topo: Fix SNC topology mess") Signed-off-by: Sasha Levin

x86/sev: Allow IBPB-on-Entry feature for SNP guests

2026-03-12T11:09:31+00:00

commit 9073428bb204d921ae15326bb7d4558d9d269aab upstream. The SEV-SNP IBPB-on-Entry feature does not require a guest-side implementation. It was added in Zen5 h/w, after the first SNP Zen implementation, and thus was not accounted for when the initial set of SNP features were added to the kernel. In its abundant precaution, commit 8c29f0165405 ("x86/sev: Add SEV-SNP guest feature negotiation support") included SEV_STATUS' IBPB-on-Entry bit as a reserved bit, thereby masking guests from using the feature. Allow guests to make use of IBPB-on-Entry when supported by the hypervisor, as the bit is now architecturally defined and safe to expose. Fixes: 8c29f0165405 ("x86/sev: Add SEV-SNP guest feature negotiation support") Signed-off-by: Kim Phillips Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Nikunj A Dadhania Reviewed-by: Tom Lendacky Cc: stable@kernel.org Link: https://patch.msgid.link/20260203222405.4065706-2-kim.phillips@amd.com Signed-off-by: Greg Kroah-Hartman

x86/efi: defer freeing of boot services memory

2026-03-12T11:09:30+00:00

commit a4b0bf6a40f3c107c67a24fbc614510ef5719980 upstream. efi_free_boot_services() frees memory occupied by EFI_BOOT_SERVICES_CODE and EFI_BOOT_SERVICES_DATA using memblock_free_late(). There are two issue with that: memblock_free_late() should be used for memory allocated with memblock_alloc() while the memory reserved with memblock_reserve() should be freed with free_reserved_area(). More acutely, with CONFIG_DEFERRED_STRUCT_PAGE_INIT=y efi_free_boot_services() is called before deferred initialization of the memory map is complete. Benjamin Herrenschmidt reports that this causes a leak of ~140MB of RAM on EC2 t3a.nano instances which only have 512MB or RAM. If the freed memory resides in the areas that memory map for them is still uninitialized, they won't be actually freed because memblock_free_late() calls memblock_free_pages() and the latter skips uninitialized pages. Using free_reserved_area() at this point is also problematic because __free_page() accesses the buddy of the freed page and that again might end up in uninitialized part of the memory map. Delaying the entire efi_free_boot_services() could be problematic because in addition to freeing boot services memory it updates efi.memmap without any synchronization and that's undesirable late in boot when there is concurrency. More robust approach is to only defer freeing of the EFI boot services memory. Split efi_free_boot_services() in two. First efi_unmap_boot_services() collects ranges that should be freed into an array then efi_free_boot_services() later frees them after deferred init is complete. Link: https://lore.kernel.org/all/ec2aaef14783869b3be6e3c253b2dcbf67dbc12a.camel@kernel.crashing.org Fixes: 916f676f8dc0 ("x86, efi: Retain boot service code until after switching to virtual mode") Cc: Signed-off-by: Mike Rapoport (Microsoft) Reviewed-by: Benjamin Herrenschmidt Signed-off-by: Ard Biesheuvel Signed-off-by: Greg Kroah-Hartman

KVM: x86: Add x2APIC "features" to control EOI broadcast suppression

2026-03-12T11:09:27+00:00

[ Upstream commit 6517dfbcc918f970a928d9dc17586904bac06893 ] Add two flags for KVM_CAP_X2APIC_API to allow userspace to control support for Suppress EOI Broadcasts when using a split IRQCHIP (I/O APIC emulated by userspace), which KVM completely mishandles. When x2APIC support was first added, KVM incorrectly advertised and "enabled" Suppress EOI Broadcast, without fully supporting the I/O APIC side of the equation, i.e. without adding directed EOI to KVM's in-kernel I/O APIC. That flaw was carried over to split IRQCHIP support, i.e. KVM advertised support for Suppress EOI Broadcasts irrespective of whether or not the userspace I/O APIC implementation supported directed EOIs. Even worse, KVM didn't actually suppress EOI broadcasts, i.e. userspace VMMs without support for directed EOI came to rely on the "spurious" broadcasts. KVM "fixed" the in-kernel I/O APIC implementation by completely disabling support for Suppress EOI Broadcasts in commit 0bcc3fb95b97 ("KVM: lapic: stop advertising DIRECTED_EOI when in-kernel IOAPIC is in use"), but didn't do anything to remedy userspace I/O APIC implementations. KVM's bogus handling of Suppress EOI Broadcast is problematic when the guest relies on interrupts being masked in the I/O APIC until well after the initial local APIC EOI. E.g. Windows with Credential Guard enabled handles interrupts in the following order: 1. Interrupt for L2 arrives. 2. L1 APIC EOIs the interrupt. 3. L1 resumes L2 and injects the interrupt. 4. L2 EOIs after servicing. 5. L1 performs the I/O APIC EOI. Because KVM EOIs the I/O APIC at step #2, the guest can get an interrupt storm, e.g. if the IRQ line is still asserted and userspace reacts to the EOI by re-injecting the IRQ, because the guest doesn't de-assert the line until step #4, and doesn't expect the interrupt to be re-enabled until step #5. Unfortunately, simply "fixing" the bug isn't an option, as KVM has no way of knowing if the userspace I/O APIC supports directed EOIs, i.e. suppressing EOI broadcasts would result in interrupts being stuck masked in the userspace I/O APIC due to step #5 being ignored by userspace. And fully disabling support for Suppress EOI Broadcast is also undesirable, as picking up the fix would require a guest reboot, *and* more importantly would change the virtual CPU model exposed to the guest without any buy-in from userspace. Add KVM_X2APIC_ENABLE_SUPPRESS_EOI_BROADCAST and KVM_X2APIC_DISABLE_SUPPRESS_EOI_BROADCAST flags to allow userspace to explicitly enable or disable support for Suppress EOI Broadcasts. This gives userspace control over the virtual CPU model exposed to the guest, as KVM should never have enabled support for Suppress EOI Broadcast without userspace opt-in. Not setting either flag will result in legacy quirky behavior for backward compatibility. Disallow fully enabling SUPPRESS_EOI_BROADCAST when using an in-kernel I/O APIC, as KVM's history/support is just as tragic. E.g. it's not clear that commit c806a6ad35bf ("KVM: x86: call irq notifiers with directed EOI") was entirely correct, i.e. it may have simply papered over the lack of Directed EOI emulation in the I/O APIC. Note, Suppress EOI Broadcasts is defined only in Intel's SDM, not in AMD's APM. But the bit is writable on some AMD CPUs, e.g. Turin, and KVM's ABI is to support Directed EOI (KVM's name) irrespective of guest CPU vendor. Fixes: 7543a635aa09 ("KVM: x86: Add KVM exit for IOAPIC EOIs") Closes: https://lore.kernel.org/kvm/7D497EF1-607D-4D37-98E7-DAF95F099342@nutanix.com Cc: stable@vger.kernel.org Suggested-by: David Woodhouse Signed-off-by: Khushit Shah Link: https://patch.msgid.link/20260123125657.3384063-1-khushit.shah@nutanix.com [sean: clean up minor formatting goofs and fix a comment typo] Co-developed-by: Sean Christopherson Signed-off-by: Sean Christopherson Signed-off-by: Sasha Levin

x86/cfi: Fix CFI rewrite for odd alignments

2026-03-12T11:09:11+00:00

[ Upstream commit 24c8147abb39618d74fcc36e325765e8fe7bdd7a ] Rustam reported his clang builds did not boot properly; turns out his .config has: CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_64B=y set. Fix up the FineIBT code to deal with this unusual alignment. Fixes: 931ab63664f0 ("x86/ibt: Implement FineIBT") Reported-by: Rustam Kovhaev Signed-off-by: Peter Zijlstra (Intel) Tested-by: Rustam Kovhaev Signed-off-by: Sasha Levin

x86/bug: Handle __WARN_printf() trap in early_fixup_exception()

2026-03-12T11:09:10+00:00

[ Upstream commit a0cb371b521dde44f32cfe954b6ef6f82b407393 ] The commit 5b472b6e5bd9 ("x86_64/bug: Implement __WARN_printf()") implemented __WARN_printf(), which changed the mechanism to use UD1 instead of UD2. However, it only handles the trap in the runtime IDT handler, while the early booting IDT handler lacks this handling. As a result, the usage of WARN() before the runtime IDT setup can lead to kernel crashes. Since KMSAN is enabled after the runtime IDT setup, it is safe to use handle_bug() directly in early_fixup_exception() to address this issue. Fixes: 5b472b6e5bd9 ("x86_64/bug: Implement __WARN_printf()") Signed-off-by: Hou Wenlong Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/c4fb3645f60d3a78629d9870e8fcc8535281c24f.1768016713.git.houwenlong.hwl@antgroup.com Signed-off-by: Sasha Levin

x86/fgraph,bpf: Switch kprobe_multi program stack unwind to hw_regs path

2026-02-26T23:00:48+00:00

[ Upstream commit aea251799998aa1b78eacdfb308f18ea114ea5b3 ] Mahe reported missing function from stack trace on top of kprobe multi program. The missing function is the very first one in the stacktrace, the one that the bpf program is attached to. # bpftrace -e 'kprobe:__x64_sys_newuname* { print(kstack)}' Attaching 1 probe... do_syscall_64+134 entry_SYSCALL_64_after_hwframe+118 ('*' is used for kprobe_multi attachment) The reason is that the previous change (the Fixes commit) fixed stack unwind for tracepoint, but removed attached function address from the stack trace on top of kprobe multi programs, which I also overlooked in the related test (check following patch). The tracepoint and kprobe_multi have different stack setup, but use same unwind path. I think it's better to keep the previous change, which fixed tracepoint unwind and instead change the kprobe multi unwind as explained below. The bpf program stack unwind calls perf_callchain_kernel for kernel portion and it follows two unwind paths based on X86_EFLAGS_FIXED bit in pt_regs.flags. When the bit set we unwind from stack represented by pt_regs argument, otherwise we unwind currently executed stack up to 'first_frame' boundary. The 'first_frame' value is taken from regs.rsp value, but ftrace_caller and ftrace_regs_caller (ftrace trampoline) functions set the regs.rsp to the previous stack frame, so we skip the attached function entry. If we switch kprobe_multi unwind to use the X86_EFLAGS_FIXED bit, we set the start of the unwind to the attached function address. As another benefit we also cut extra unwind cycles needed to reach the 'first_frame' boundary. The speedup can be measured with trigger bench for kprobe_multi program and stacktrace support. - trigger bench with stacktrace on current code: kprobe-multi : 0.810 ± 0.001M/s kretprobe-multi: 0.808 ± 0.001M/s - and with the fix: kprobe-multi : 1.264 ± 0.001M/s kretprobe-multi: 1.401 ± 0.002M/s With the fix, the entry probe stacktrace: # bpftrace -e 'kprobe:__x64_sys_newuname* { print(kstack)}' Attaching 1 probe... __x64_sys_newuname+9 do_syscall_64+134 entry_SYSCALL_64_after_hwframe+118 The return probe skips the attached function, because it's no longer on the stack at the point of the unwind and this way is the same how standard kretprobe works. # bpftrace -e 'kretprobe:__x64_sys_newuname* { print(kstack)}' Attaching 1 probe... do_syscall_64+134 entry_SYSCALL_64_after_hwframe+118 Fixes: 6d08340d1e35 ("Revert "perf/x86: Always store regs->ip in perf_callchain_kernel()"") Reported-by: Mahe Tardy Signed-off-by: Jiri Olsa Signed-off-by: Andrii Nakryiko Acked-by: Steven Rostedt (Google) Link: https://lore.kernel.org/bpf/20260126211837.472802-3-jolsa@kernel.org Signed-off-by: Sasha Levin

x86/vmware: Fix hypercall clobbers

2026-02-06T22:51:03+00:00

Fedora QA reported the following panic: BUG: unable to handle page fault for address: 0000000040003e54 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS edk2-20251119-3.fc43 11/19/2025 RIP: 0010:vmware_hypercall4.constprop.0+0x52/0x90 .. Call Trace: vmmouse_report_events+0x13e/0x1b0 psmouse_handle_byte+0x15/0x60 ps2_interrupt+0x8a/0xd0 ... because the QEMU VMware mouse emulation is buggy, and clears the top 32 bits of %rdi that the kernel kept a pointer in. The QEMU vmmouse driver saves and restores the register state in a "uint32_t data[6];" and as a result restores the state with the high bits all cleared. RDI originally contained the value of a valid kernel stack address (0xff5eeb3240003e54). After the vmware hypercall it now contains 0x40003e54, and we get a page fault as a result when it is dereferenced. The proper fix would be in QEMU, but this works around the issue in the kernel to keep old setups working, when old kernels had not happened to keep any state in %rdi over the hypercall. In theory this same issue exists for all the hypercalls in the vmmouse driver; in practice it has only been seen with vmware_hypercall3() and vmware_hypercall4(). For now, just mark RDI/RSI as clobbered for those two calls. This should have a minimal effect on code generation overall as it should be rare for the compiler to want to make RDI/RSI live across hypercalls. Reported-by: Justin Forbes Link: https://lore.kernel.org/all/99a9c69a-fc1a-43b7-8d1e-c42d6493b41f@broadcom.com/ Signed-off-by: Josh Poimboeuf Cc: stable@kernel.org Signed-off-by: Linus Torvalds