diff options
| author | Sean Christopherson <seanjc@google.com> | 2024-10-09 21:23:44 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2024-10-20 13:31:05 +0200 |
| commit | 28cf4978810791bf30288e59f1b9dc31eeeb68e6 (patch) | |
| tree | 0fe47886db570be6d0822a25958ffaa62aec681e /arch/x86 | |
| parent | KVM: x86/mmu: Zap only SPs that shadow gPTEs when deleting memslot (diff) | |
| download | linux-28cf4978810791bf30288e59f1b9dc31eeeb68e6.tar.xz linux-28cf4978810791bf30288e59f1b9dc31eeeb68e6.zip | |
KVM: x86/mmu: Add lockdep assert to enforce safe usage of kvm_unmap_gfn_range()
Add a lockdep assertion in kvm_unmap_gfn_range() to ensure that either
mmu_invalidate_in_progress is elevated, or that the range is being zapped
due to memslot removal (loosely detected by slots_lock being held).
Zapping SPTEs without mmu_invalidate_{in_progress,seq} protection is unsafe
as KVM's page fault path snapshots state before acquiring mmu_lock, and
thus can create SPTEs with stale information if vCPUs aren't forced to
retry faults (due to seeing an in-progress or past MMU invalidation).
Memslot removal is a special case, as the memslot is retrieved outside of
mmu_invalidate_seq, i.e. doesn't use the "standard" protections, and
instead relies on SRCU synchronization to ensure any in-flight page faults
are fully resolved before zapping SPTEs.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20241009192345.1148353-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kvm/mmu/mmu.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 09494d01c38e..8e853a5fc867 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -1556,6 +1556,17 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range) { bool flush = false; + /* + * To prevent races with vCPUs faulting in a gfn using stale data, + * zapping a gfn range must be protected by mmu_invalidate_in_progress + * (and mmu_invalidate_seq). The only exception is memslot deletion; + * in that case, SRCU synchronization ensures that SPTEs are zapped + * after all vCPUs have unlocked SRCU, guaranteeing that vCPUs see the + * invalid slot. + */ + lockdep_assert_once(kvm->mmu_invalidate_in_progress || + lockdep_is_held(&kvm->slots_lock)); + if (kvm_memslots_have_rmaps(kvm)) flush = __kvm_rmap_zap_gfn_range(kvm, range->slot, range->start, range->end, |