kernel/linux.git/arch, branch master

Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

2026-05-03T22:25:47+00:00

Pull kvm fixes from Paolo Bonzini: "Three bug fixes for x86: - Check that nEPT/nNPT is enabled in slow flush hypercalls. If it is not, the hypercalls can be processed as usual even while running a nested guest - Fix shadow paging use-after-free due to page tables changing outside execution of the guest. A bug that is 16 years old and stems from an imprecision in the very first KVM series - Scan IRR whenever PID.ON is true, even if PIR is empty, which avoids a somewhat rare WARN" * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: KVM: x86: Fix shadow paging use-after-free due to unexpected GFN KVM: x86: Fix misleading variable names and add more comments for PIR=>IRR flow KVM: x86: Do IRR scan in __kvm_apic_update_irr even if PIR is empty KVM: x86: check for nEPT/nNPT in slow flush hypercalls

KVM: x86: Fix shadow paging use-after-free due to unexpected GFN

2026-05-03T20:32:53+00:00

The shadow MMU computes GFNs for direct shadow pages using sp->gfn plus the SPTE index. This assumption breaks for shadow paging if the guest page tables are modified between VM entries (similar to commit aad885e77496, "KVM: x86/mmu: Drop/zap existing present SPTE even when creating an MMIO SPTE", 2026-03-27). The flow is as follows: - a PDE is installed for a 2MB mapping, and a page in that area is accessed. KVM creates a kvm_mmu_page consisting of 512 4KB pages; the kvm_mmu_page is marked by FNAME(fetch) as direct-mapped because the guest's mapping is a huge page (and thus contiguous). - the PDE mapping is changed from outside the guest. - the guest accesses another page in the same 2MB area. KVM installs a new leaf SPTE and rmap entry; the SPTE uses the "correct" GFN (i.e. based on the new mapping, as changed in the previous step) but that GFN is outside of the [sp->gfn, sp->gfn + 511] range; therefore the rmap entry cannot be found and removed when the kvm_mmu_page is zapped. - the memslot that covers the first 2MB mapping is deleted, and the kvm_mmu_page for the now-invalid GPA is zapped. However, rmap_remove() only looks at the [sp->gfn, sp->gfn + 511] range established in step 1, and fails to find the rmap entry that was recorded by step 3. - any operation that causes an rmap walk for the same page accessed by step 3 then walks a stale rmap and dereferences a freed kvm_mmu_page. This includes dirty logging or MMU notifier invalidations (e.g., from MADV_DONTNEED). The underlying issue is that KVM's walking of shadow PTEs assumes that if a SPTE is present when KVM wants to install a non-leaf SPTE, then the existing kvm_mmu_page must be for the correct gfn. Because the only way for the gfn to be wrong is if KVM messed up and failed to zap a SPTE... which shouldn't happen, but *actually* only happens in response to a guest write. That bug dates back literally forever, as even the first version of KVM assumes that the GFN matches and walks into the "wrong" shadow page. However, that was only an imprecision until 2032a93d66fa ("KVM: MMU: Don't allocate gfns page for direct mmu pages") came along. Fix it by checking for a target gfn mismatch and zapping the existing SPTE. That way the old SP and rmap entries are gone, KVM installs the rmap in the right location, and everyone is happy. Fixes: 2032a93d66fa ("KVM: MMU: Don't allocate gfns page for direct mmu pages") Fixes: 6aa8b732ca01 ("kvm: userspace interface") Reported-by: Alexander Bulekov Reported-by: Fred Griffoul Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson Link: https://patch.msgid.link/20260503201029.106481-1-pbonzini@redhat.com/ Signed-off-by: Paolo Bonzini

KVM: x86: Fix misleading variable names and add more comments for PIR=>IRR flow

2026-05-03T20:32:41+00:00

Rename kvm_apic_update_irr()'s "irr_updated" and vmx_sync_pir_to_irr()'s "got_posted_interrupt" to a more accurate "max_irr_is_from_pir", as neither "irr_updated" nor "got_posted_interrupt" is accurate. __kvm_apic_update_irr() and thus kvm_apic_update_irr() specifically return true if and only if the highest priority IRQ, i.e. max_irr, is a "new" pending IRQ from the PIR. I.e. it's possible for the IRR to be updated, i.e. for a posted IRQ to be "got", *without* the APIs returning true. Expand vmx_sync_pir_to_irr()'s comment to explain why it's necessary to set KVM_REQ_EVENT only if a "new" IRQ was found, and to explain why it's safe to do so only if a new IRQ is also the highest priority pending IRQ. No functional change intended. Signed-off-by: Sean Christopherson Link: https://patch.msgid.link/20260503201703.108231-3-pbonzini@redhat.com/ Signed-off-by: Paolo Bonzini

KVM: x86: Do IRR scan in __kvm_apic_update_irr even if PIR is empty

2026-05-03T20:18:15+00:00

Fall back to apic_find_highest_vector() when PID.ON is set but PIR turns out to be empty, to correctly report the highest pending interrupt from the existing IRR. In a nested VM stress test, the following WARNING fires in vmx_check_nested_events() when kvm_cpu_has_interrupt() reports a pending interrupt but the subsequent kvm_apic_has_interrupt() (which invokes vmx_sync_pir_to_irr() again) returns -1: WARNING: CPU: 99 PID: 57767 at arch/x86/kvm/vmx/nested.c:4449 vmx_check_nested_events+0x6bf/0x6e0 [kvm_intel] Call Trace: kvm_check_and_inject_events vcpu_enter_guest.constprop.0 vcpu_run kvm_arch_vcpu_ioctl_run kvm_vcpu_ioctl __x64_sys_ioctl do_syscall_64 entry_SYSCALL_64_after_hwframe The root cause is a race between vmx_sync_pir_to_irr() on the target vCPU and __vmx_deliver_posted_interrupt() on a sender vCPU. The sender performs two individually-atomic operations that are not a single transaction: 1. pi_test_and_set_pir(vector) -- sets the PIR bit 2. pi_test_and_set_on() -- sets PID.ON The following interleaving triggers the bug: Sender vCPU (IPI): Target vCPU (1st sync_pir_to_irr): B1: set PIR[vector] A1: pi_clear_on() A2: pi_harvest_pir() -> sees B1 bit A3: xchg() -> consumes bit, PIR=0 (1st sync returns correct max_irr) B2: set PID.ON = 1 Target vCPU (2nd sync_pir_to_irr): C1: pi_test_on() -> TRUE (from B2) C2: pi_clear_on() -> ON=0 C3: pi_harvest_pir() -> PIR empty C4: *max_irr = -1, early return IRR NOT SCANNED The interrupt is not lost (it resides in the IRR from the first sync and is recovered on the next vcpu_enter_guest() iteration), but the incorrect max_irr causes a spurious WARNING and a wasted L2 VM-Enter/VM-Exit cycle. Fixes: b41f8638b9d3 ("KVM: VMX: Isolate pure loads from atomic XCHG when processing PIR") Reported-by: Farrah Chen Analyzed-by: Chenyi Qiang Cc: stable@vger.kernel.org Reviewed-by: Sean Christopherson Link: https://lore.kernel.org/kvm/20260428070349.1633238-1-chenyi.qiang@intel.com/T/ Link: https://patch.msgid.link/20260503201703.108231-2-pbonzini@redhat.com/ Signed-off-by: Paolo Bonzini

KVM: x86: check for nEPT/nNPT in slow flush hypercalls

2026-05-03T20:17:30+00:00

Checking is_guest_mode(vcpu) is incorrect, because translate_nested_gpa() is only valid if an L2 guest is running *with nested EPT/NPT enabled*. Instead use the same condition as translate_nested_gpa() itself. Cc: stable@vger.kernel.org Reviewed-by: Sean Christopherson Fixes: aee738236dca ("KVM: x86: Prepare kvm_hv_flush_tlb() to handle L2's GPAs", 2022-11-18) Link: https://patch.msgid.link/20260503200905.106077-1-pbonzini@redhat.com/ Signed-off-by: Paolo Bonzini

Merge tag 'sh-for-v7.1-tag2' of git://git.kernel.org/pub/scm/linux/kernel/git/glaubitz/sh-linux

2026-05-03T15:58:42+00:00

Pull sh fix from John Paul Adrian Glaubitz: "The ZERO_PAGE consolidation in v7.1, introduced a regression on sh which made these systems unbootable. The problem was that on sh, the initial boot parameters were previously referenced as an array and after 6215d9f4470f ("arch, mm: consolidate empty_zero_page"), they were referenced as a pointer which caused wrong code generation and boot hang. This changes the declaration back to being an array which fixes the boot hang" * tag 'sh-for-v7.1-tag2' of git://git.kernel.org/pub/scm/linux/kernel/git/glaubitz/sh-linux: sh: Fix fallout from ZERO_PAGE consolidation

sh: Fix fallout from ZERO_PAGE consolidation

2026-05-03T14:35:40+00:00

Consolidation of empty_zero_page declarations broke boot on sh. sh stores its initial boot parameters in a page reserved in arch/sh/kernel/head_32.S. Before commit 6215d9f4470f ("arch, mm: consolidate empty_zero_page") this page was referenced in C code as an array and after that commit it is referenced as a pointer. This causes wrong code generation and boot hang. Declare boot_params_page as an array to fix the issue. Reported-by: Thomas Weißschuh Tested-by: Thomas Weißschuh Fixes: 6215d9f4470f ("arch, mm: consolidate empty_zero_page") Signed-off-by: Mike Rapoport (Microsoft) Reviewed-by: John Paul Adrian Glaubitz Tested-by: Geert Uytterhoeven Tested-by: Artur Rojek Signed-off-by: John Paul Adrian Glaubitz

Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

2026-05-01T23:32:42+00:00

Pull arm64 fixes from Catalin Marinas: - Avoid writing an uninitialised stack variable to POR_EL0 on sigreturn if the poe_context record is absent - Reserve one more page for the early 4K-page kernel mapping to cover the extra [_text, _stext) split introduced by the non-executable read-only mapping - Force the arch_local_irq_*() wrappers to be __always_inline so that noinstr entry and idle paths cannot call out-of-line, instrumentable copies - Fix potential sign extension in the arm64 SCS unwinder's DWARF advance_loc4 decoding - Tolerate arm64 ACPI platforms with only WFI and no deeper PSCI idle states, restoring cpuidle registration on such systems - Include the UAPI header in the arm64 GCS libc test rather than carrying a duplicate struct user_gcs definition (the original #ifdef NT_ARM_GCS was wrong to cover the structure definition as it would be masked out if the toolchain defined it) * tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: arm64: signal: Preserve POR_EL0 if poe_context is missing arm64: Reserve an extra page for early kernel mapping kselftest/arm64: Include for user_gcs definition ACPI: arm64: cpuidle: Tolerate platforms with no deep PSCI idle states arm64/irqflags: __always_inline the arch_local_irq_*() helpers arm64/scs: Fix potential sign extension issue of advance_loc4

Merge tag 's390-7.1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

2026-05-01T19:58:02+00:00

Pull s390 fixes from Alexander Gordeev: - Reject zero-length writes from userspace that corrupt Debug Facility buffers - Replace one s390 PCI maintainer - Remove SCLP_OFB Kconfig option and enable the guarded code unconditionally - Replace incorrect use of phys_to_folio() to virt_to_folio() in do_secure_storage_access() * tag 's390-7.1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: s390/mm: Fix phys_to_folio() usage in do_secure_storage_access() s390/sclp: Remove SCLP_OFB Kconfig option MAINTAINERS: Replace one of the maintainers for s390/pci s390/debug: Reject zero-length input in debug_input_flush_fn() s390/debug: Reject zero-length input before trimming a newline

arm64: signal: Preserve POR_EL0 if poe_context is missing

2026-05-01T16:44:25+00:00

Commit 2e8a1acea859 ("arm64: signal: Improve POR_EL0 handling to avoid uaccess failures") delayed the write to POR_EL0 in rt_sigreturn to avoid spurious uaccess failures. This change however relies on the poe_context frame record being present: on a system supporting POE, calling sigreturn without a poe_context record now results in writing arbitrary data from the kernel stack into POR_EL0. Fix this by adding a __valid_fields member to struct user_access_state, and zeroing the struct on allocation. restore_poe_context() then indicates that the por_el0 field is valid by setting the corresponding bit in __valid_fields, and restore_user_access_state() only touches POR_EL0 if there is a valid value to set it to. This is in line with how POR_EL0 was originally handled; all frame records are currently optional, except fpsimd_context. To ensure that __valid_fields is kept in sync, fields (currently just por_el0) are now accessed via accessors and prefixed with __ to discourage direct access. Fixes: 2e8a1acea859 ("arm64: signal: Improve POR_EL0 handling to avoid uaccess failures") Cc: Reported-by: Will Deacon Signed-off-by: Kevin Brodsky Signed-off-by: Catalin Marinas