kernel/git/next/linux-next.git/virt, branch master

KVM: pfncache: use a dedicated invalidation sequence for cache refresh

2026-09-04T15:34:07+00:00

The gfn_to_pfn_cache refresh path guards against mmu notifier invalidations which complete while it has dropped gpc->lock for the HVA->PFN lookup: hva_to_pfn_retry() samples kvm->mmu_invalidate_seq and retries if it changed, or if mn_active_invalidate_count is still elevated. That is insufficient for HVA-based caches. mmu_invalidate_seq is only advanced by kvm_mmu_invalidate_end() when the invalidated range overlaps a memslot, and an HVA-based cache (e.g. the Xen shared_info page mapped with KVM_XEN_ATTR_TYPE_SHARED_INFO_HVA) need not be backed by any memslot at all. An invalidation of the cached HVA which starts and ends entirely within the lookup window is thus invisible to the retry check: mn_active_invalidate_count is back to zero and the sequence never moved. The refresh then publishes a mapping of a page which has already been freed, and the next reader dereferences it: BUG: KASAN: use-after-free in kvm_xen_shared_info_init+0x3c6/0x440 Read of size 4 at addr ffff8880599c2900 by task syz.2.383/7257 Since gfn_to_pfn_cache_invalidate_start() deliberately skips caches which are not currently valid (including one whose refresh is in progress, as the refresh clears the valid flag before dropping the lock), the retry check is the only line of defence, and it must fire for *any* invalidation, not just those hitting a memslot. Add a dedicated kvm->gpc_invalidate_seq, incremented by every kvm_mmu_notifier_invalidate_range_end() under mn_invalidate_lock before mn_active_invalidate_count is decremented, and check it in hva_to_pfn_retry() instead of mmu_invalidate_seq. Incrementing in range_end() in the same critical section as the in-progress count also closes the variant where the cache is activated with the contested HVA only after invalidate_range_start() has run. The same bug is also reachable through the per-vCPU vcpu_info cache (KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA), where the stale mapping is then dereferenced by kvm_setup_guest_pvclock() on the next KVM_RUN: BUG: KASAN: use-after-free in kvm_setup_guest_pvclock+0x5bf/0x660 This intentionally makes refresh retry on *unrelated* mmu notifier events; restoring precision (and reworking the GPC locking more generally) is left for a subsequent series. Reproducers: https://david.woodhou.se/xen_shinfo_race.c https://david.woodhou.se/vcpu_info_race.c Suggested-by: Sean Christopherson Reported-by: syzbot+0948c82180d475ad24e2@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/6a0c5f2c.a00a0220.2c7954.0000.GAE@google.com/ Tested-by: syzbot+0948c82180d475ad24e2@syzkaller.appspotmail.com Reported-by: syzbot+fb7c2dd166d3ea63df2a@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/6a426dd2.854d4ab9.360e1d.0008.GAE@google.com/ Fixes: b9220d32799a ("KVM: x86/xen: allow shared_info to be mapped by fixed HVA") Cc: stable@vger.kernel.org Signed-off-by: David Woodhouse Assisted-by: Claude:claude-mythos-5 Reviewed-by: Paul Durrant Link: https://patch.msgid.link/20260831213632.81023-13-dwmw2@infradead.org Signed-off-by: Paolo Bonzini

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

2026-08-25T18:48:04+00:00

Pull kvm updates from Paolo Bonzini: "ARM64: - Add support for 'slot' based PMU events, paired with new UAPI that compels the user to select a specific PMU implementation - Lazy save/restore of vCPU state for pKVM, along with various fixes and cleanups to the management of vCPU state between the untrusted host and pKVM hypervisor - Disable traps of EL1 registers for nested hypervisors when FEAT_NV2p1 is present, guaranteeing that EL2-specific register bits are stateful in the EL1 counterpart - Leverage FEAT_NV3 to avoid unnecessary ERET/TLBI traps when the scope of those instructions remains 'in host' (i.e. L1 kernel/userspace) - Pile of fixes for the management of the VNCR pseudo-TLB, such as under-invalidations and races with concurrent TLBIs on other vCPUs - Consolidate the non-protected and pKVM view of ICH_VTR_EL2 to a runtime-patched constant, allowing the same data to be shared with pKVM prior to dropping host privileges - Considerable pile of LLM-assisted fixes around the shop but mostly in the VGIC, our in-kernel generator of bugs (and sometimes interrupts) LoongArch: - Advertise already-supported capabilities - Some bug fixes about timer and MMIO - Some hardening about interrupt injection - Replace kvm_err() with kvm_pr_unimpl() - Add FPU/LSX/LASX test cases for selftests RISC-V: - Svadu/Zicfiss/Zicfilp FWFT support for Guest - Use try_cmpxchg for IMSIC MRIF RMW - More arch-specific tracepoints in KVM RISC-V - Eager page splitting when enabling dirty logging - Optimize hfence request handling for SMP Guests - Improve dirty log clearing by skipping zero bits in mask - Guard HFENCE range loops against overflow - CPU PM notifiers in KVM RISC-V for non-retentive idle states - Fix kernel-mode vector context save/restore for Guest s390: - Fixes for vfio-ap - Fixes for the gmap rework - Fixes for vsie - AI triggered fixes all over - diag9c tracing - code move preparation for the additional arm64 support - enable CONTEXT_ANALYSIS x86: - Perform spring cleaning on x86.{c,h} and asm/kvm_host.h, by adding regs.c (the kvm_cache_regs.h => regs.h is already applied) and msrs.{c,h}, and moving relevant code out of x86.c - Split kvm_mmu in three parts, respectively to describe the format of page tables, walking the guest page tables and building the page tables. Always use the same page table walker kvm->arch.gva_walk as the entry point to convert a guest's virtual address, where the previous code used two different kvm_mmu structs depending on whether the walk included nested EPT/NPT or not. Make page fault vmexits reuse the permission checking machinery that is used for guest page faults. This is both a cleanup and a baby step towards supporting XS/XU memory permissions - Document some of the "fun" gotchas with the APIC base when creating IRQCHIPs on x86 - Remove a defunct masterclock update from kvm_xen_shared_info_init(). It could result in incorrect kvmclock due to triggering an unnecessary switch to/from masterclock mode - Skip Xen runstate time updates if time has effectively gone backwards, so that the guest doesn't report 100% steal time for a very, very long time - Drop KVM's runtime updates of the Xen PV timing CPUID leaf, as KVM was updating the wrong sub-leaf, and upstream KVM will soon provide all the information needed by userspace to populate the CPUID field itself - Fix a bug where KVM would walk a newly created rmap without holding the rmap lock (or mmu_lock) during aging - Fix a bug where aging TDP MMU SPTEs could clobber FROZEN SPTEs - Fix a variety of #DB priority bugs - Fix a class of races related to enabling Hyper-V emulation on a vCPU after the vCPU is visible to the rest of KVM - Use static calls for nested virtualization ops - Move more KVM-internal code out of x86's kvm_host.h - Enumerate support for a variety of Zhaoxin instructions that don't require explicit virtualization - Fix missing EFER validation bugs, including in the KVM_SET_SREGS* path - Harden kvm_vcpu_map() against double-mapping and thus leaking references - Misc fixes and cleanups, e.g. for largely benign syzkaller splats x86 (Intel): - Zero a vCPU's entry in VMX's Posted Interrupt Descriptor table used for IPI virtualization when the vCPU is freed, to fix a use-after-free where hardware will write to a freed vCPU's PID - Service local TLB flushes on a failed nested VM-Enter to fix a bug where KVM could miss a TLB on a future, successful VM-Enter with the same L2 VPID - Cap the maximum value shoved into the VMX Preemption Timer to workaround an erratum that affects all existing Intel CPUs that support CPUID 0x15 - Fix VPID virtualization bugs where KVM would fail to flush hardware TLBs - Harden the TDX "populate" ioctls against bad input, and to prepare for supporting in-place private<=>shared conversion x86 (AMD): - Forcefully invalidate SNP VMSA pages if their backing guest_memfd page is zapped/invalidated, e.g. due to a PUNCH_HOLE in response to a Page-State Change request - Remove a dying VM from the GA Log notifier list before the VM is actually destroyed, to fix a potential use-after-free - While FOLL_WRITE was needed in the past to trigger CoW unsharing, nowadays FOLL_LONGTERM does that already even without FOLL_WRITE, and in fact, get_user_pages() actually disallows FOLL_WRITE together with FOLL_LONGTERM. So don't pass FOLL_WRITE when registering encrypted memory regions, i.e. when pinning SEV/SEV-ES guest memory, to fix a regression with file-backed memory introduced by KVM's (correct) usage of long-term pins (This was reviewed by mm maintainers; for more information, see commit ee1a586dd1fa "KVM: SEV: Drop FOLL_WRITE for encrypted region registration") - Allocate full pages for SEV/SEV-ES {DE,EN}CRYPT ops on SNP-enabled hosts to fix a data corruption issue due to the PSP driver assigning to-be-written pages to firmware (as required by the SNP specs) - Unconditionally intercept ICBEP so that KVM generates the correct guest RIP when handling an ICEBP-induced TASK_SWITCH #VMEXIT - Harden the SNP "populate" ioctls against bad input, and to prepare for supporting in-place private<=>shared conversion Generic: - Remove kvm_debugfs_dir if kvm_init() fails after creating KVM's debugfs - Add a per-VM bitmap to track which vCPU IDs have been "claimed" but for which the vCPU isn't yet online, and use the bitmap to reject duplicate IDs before calling into arch code. This allows arch code to consume vcpu_id without having to worry about cross-vCPU clobbering (at least s390 and x86 have had related bugs) - Rework the so called "prepare" and "invalidate" guest_memfd hooks to prepare for in-place private<=>shared conversion, and clean up a few warts along the way Selftests: - Automatically allocate a full page for L2 guest stacks on x86 instead of requiring test-specific L1 guest code to carve out a portion of the L1 stack for L2 usage, and to ensure the L2 stack also adheres to the x86-64 calling convention ABI - Add a selftest to verify {Guest,Host}-Only behavior in x86's mediated PMU - Clean up nested SVM's handling of GPRs on L2<=>L1 transitions, reuse the functionality for nested VMX, and drop the ucall hack that was fudging around the lack of GPR switching on nVMX - Add a stress test to verify KVM doesn't clobber/drop #PF state, e.g. CR2, across save/restore, including when L2 is active - Add a test to verify KVM_CREATE_VM accepts exactly what is reported by KVM_CAP_VM_TYPES - Misc selftests fixes and cleanups - Fix several issues with seeding the pRNG, and rework the pRNG APIs to that the pRNG can be sanely used in host code, not just guest code - Add an IRQ test to validate virtual IRQ deliverty for IRQs wired up via KVM_IRQFD + KVM_SET_GSI_ROUTING, with optional support for triggering IRQs via writes to an assigned VFIO device - Add syscall wrappers to assert success on a variety of pthreads and CPU affinity APIs - Set vCPU pthread affinity as early as possible to reduce contention issues that were surfaced by PREEMPT_LAZY, which result in runtimes of over a minute on large hosts, versus the expected ~5 seconds - Rework the PMU counters test to run each testcase using a single VM with many vCPUs for each sub-testcase, instead of using a unique VM for each sub-testcase. This cuts the runtime by ~20x Miscellaneous: - MAINTAINERS updates for vfio-ap, guest_memfd, kvm-x86. Mostly representing the status quo more accurately, but also... welcome David Hildenbrand as guest_memfd reviewer!" * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (413 commits) KVM: arm64: Validate GICv5 timer PPIs before claiming ownership KVM: arm64: vgic: Reject out-of-range GICv5 PPI IDs KVM: arm64: vgic: Prevent speculative SPI array underflow KVM: arm64: vgic: Free gic_kvm_info on initialization failure KVM: arm64: Avoid mismatched accesses to 'struct kvm_nvhe_init_params' s390/vfio-ap: Fix NULL deref in status_show() during queue probe s390/vfio-ap: Fix hot-unplug skipped when last AP adapter or domain removed s390/vfio-ap: fix potential use of uninitialized apm_filtered bitmap s390/vfio-ap: Fix control domain removal in vfio_ap_mdev_cfg_remove s390/vfio-ap: Fix required lock not held during update of ap_matrix_mdev object s390/vfio-ap: Fix missing lock required to access list of ap_matrix_mdev objects s390/vfio-ap: Fix dereference matrix_mdev->kvm without checking for NULL s390/vfio-ap: Fix stale do_remove flag across iterations in vfio_ap_mdev_cfg_remove RISC-V: KVM: fix vcpu vector context handling for kernel-mode vector riscv: vector: allow non-preemptible kernel-mode vector with IRQs off riscv: vector: refactor riscv_v_start_kernel_context KVM: s390: gmap: Make prefix handling optional KVM: s390: gmap: Make CMMA optional KVM: s390: gmap: Make storage keys optional KVM: s390: Prepare gmap for a second KVM implementation ...

Merge tag 'kvm-x86-misc-7.3' of https://github.com/kvm-x86/linux into HEAD

2026-08-18T11:41:51+00:00

KVM x86 misc changes for 7.3 - Fix VPID virtualization bugs where KVM would fail to flush hardware TLBs. - Harden the SNP and TDX "populate" ioctls against bad input, and to prepare for supporting in-place private<=>shared conversion. - Fix a variety of #DB priority bugs. - Fix a class of races related to enabling Hyper-V emulation on a vCPU after the vCPU is visible to the rest of KVM. - Use static calls for nested virtualization ops. - Move more KVM-internal code out of x86's kvm_host.h. - Enumerate support for a variety of Zhaoxin instructions that don't require explicit virtualization. - Fix missing EFER validation bugs, including in the KVM_SET_SREGS* path. - Harden kvm_vcpu_map() against double-mapping and thus leaking references. - Misc fixes and cleanups, e.g. for largely benign syzkaller splats.

Merge tag 'kvm-x86-coco-7.3' of https://github.com/kvm-x86/linux into HEAD

2026-08-18T11:25:39+00:00

KVM guest_memfd and x86 CoCo changes for 7.3 - Forcefully invalidate SNP VMSA pages if their backing guest_memfd page is zapped/invalidated, e.g. due to a PUNCH_HOLE in response to a Page-State Change request. - Rework the so called "prepare" and "invalidate" guest_memfd hooks to prepare for in-place private<=>shared conversion, and clean up a few warts along the way.

Merge tag 'kvm-x86-generic-7.3' of https://github.com/kvm-x86/linux into HEAD

2026-08-18T11:13:25+00:00

KVM arch-neutral and documentation changes for 7.3 - Remove kvm_debugfs_dir if kvm_init() fails after creating KVM's debugfs. - Document some of the "fun" gotchas with the APIC base when creating IRQCHIPs on x86. - Add a per-VM bitmap to track which vCPU IDs have been "claimed" but for which the vCPU isn't yet online, and use the bitmap to reject duplicate IDs before calling into arch code. This allows arch code to consume vcpu_id without having to worry about cross-vCPU clobbering (at least s390 and x86 have had related bugs). - Zero a vCPU's entry in VMX's Posted Interrupt Descriptor table used for IPI virtualization when the vCPU is freed to fix a use-after-free where hardware will write to a freed vCPU's PID.

Merge tag 'kvm-x86-maintainers-7.3' of https://github.com/kvm-x86/linux into HEAD

2026-08-18T11:10:26+00:00

KVM MAINTAINERS changes for 7.3 - Add the kvm-x86 tree to KVM x86 entries so that humans and robots alike can more easily find in-flight x86 changes. - Add a dedicated entry for guest_memfd, with the usual suspects as Maintainers, and David Hildenbrand as a Reviewer. - Add Sean as a Reviewer for overall KVM.

KVM: guest_memfd: Move gmem function declarations to dedicated guest_memfd.h

2026-08-05T17:00:53+00:00

Extract the gmem function declarations out of kvm_mm.h and into a dedicated header, guest_memfd.h. This will allow creating a MAINTAINERS entry for guest_memfd without having to rely on content pattern matching. Reviewed-by: Ackerley Tng Acked-by: David Hildenbrand (Arm) Link: https://patch.msgid.link/20260731173842.2649391-3-seanjc@google.com Signed-off-by: Sean Christopherson

mm: use linear_page_[index, delta]() consistently

2026-08-05T02:19:01+00:00

There are a number of places where we open code what linear_page_index() and linear_page_delta() calculate. Replace this code with the appropriate functions for consistency. No functional change intended. Link: https://lore.kernel.org/20260710-b4-pre-scalable-cow-v2-21-2a5aa403d977@kernel.org Signed-off-by: Lorenzo Stoakes Reviewed-by: Thomas Zimmermann [DRM] Acked-by: Kai Huang # for sgx Reviewed-by: Gregory Price Reviewed-by: Pedro Falcato # for mm Reviewed-by: Ackerley Tng [guest_memfd] Reviewed-by: Vlastimil Babka (SUSE) Cc: David Hildenbrand (Arm) Cc: Marek Szyprowski Cc: SJ Park Cc: Liam R. Howlett (Oracle) Cc: Zi Yan Signed-off-by: Andrew Morton

KVM: Check for duplicate vcpu_id as early as possible

2026-07-31T22:13:30+00:00

If userspace tries to create a vCPU with the same vcpu_id as an existing one, kvm_vm_ioctl_create_vcpu() checks for that and fails with -EEXIST only after it already created the vCPU via kvm_arch_vcpu_create(). As a result, even though this newly created vCPU is destroyed in the failure path, the fact that it is temporarily created with an invalid vcpu_id and that there are temporarily two vCPUs with the same vcpu_id is a potential source of subtle issues. In particular, this prevents fixing an VMX IPIv issue where a stale entry left in the VM's PI descriptor table after the vCPU is destroyed in the failure path. The right way to fix that issue is to clear that entry when destroying the vCPU, however right now that would have a nasty side effect: since the same entry is used for the other, previously created vCPU with same vcpu_id, clearing it would mean effectively disabling IPIv for that existing good vCPU. So to avoid this and similar problems, check for duplicate vcpu_id as early in the vCPU creation path as possible, before kvm_arch_vcpu_create() and even before kvm_arch_vcpu_precreate(). Simply moving the existing kvm_get_vcpu_by_id() check earlier doesn't work, as kvm->lock is dropped and reacquired, i.e. moving kvm_get_vcpu_by_id() would introduce a race: 1. vCPU A is being created but not installed in kvm->vcpu_array yet. 2. vCPU B with the same vcpu_id is being created. It passes the duplicated vcpu_id check, since the check doesn't find vCPU A in kvm->vcpu_array. 3. vCPU A is installed in kvm->vcpu_array, vCPU creation succeeds. 4. vCPU B with the same vcpu_id is installed in kvm->vcpu_array, vCPU creation succeeds. So introduce the bitmap of vcpu_ids used by the VM, in order to safely check if the given vcpu_id is used and mark is as used before releasing kvm->lock first time. Alternatively, KVM could use another Xarray[*] for roughly the same code complexity, which would minimize KVM's steady state memory footprint at the cost of higher runtime latency (to allocate and free entries). Given that the worst case scenario is 256 bytes per-VM (on x86, which allows up to 16KiB vCPU IDs), go with the slightly simpler approach until there's a need to save memory. Suggested-by: Sean Christopherson Link: https://lore.kernel.org/kvm/al6eg7C-2sDBEAFD@google.com [*] Signed-off-by: Dmytro Maluka Reviewed-by: Kai Huang Link: https://patch.msgid.link/20260729170621.308809-2-dmaluka@chromium.org [sean: massage changelog] Signed-off-by: Sean Christopherson

KVM: Harden kvm_vcpu_map() against double-mapping and thus leaking references

2026-07-28T20:48:46+00:00

Now that all on-stack maps use CLASS(kvm_vcpu_map_local), i.e. now that all maps are zero-allocated, explicitly put any existing mappings/references when establishing a new mapping to harden against KVM bugs leaking memory, but yell loudly as the owner of the map is still ultimately responsible for the lifecycle of the mapping. Suggested-by: Yosry Ahmed Link: https://patch.msgid.link/20260724004757.131420-7-seanjc@google.com Signed-off-by: Sean Christopherson