diff options
| author | Sean Christopherson <seanjc@google.com> | 2021-02-12 16:50:11 -0800 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2021-02-19 03:08:34 -0500 |
| commit | 52f4607940b18337f01d160aaae346eaac388bf7 (patch) | |
| tree | cffeedb01cccf2dc0d701e0c4519233140bee794 /arch | |
| parent | a018eba53870aa30e5e57465771cb209680f20c2 (diff) | |
| download | linux-52f4607940b18337f01d160aaae346eaac388bf7.tar.bz2 | |
KVM: x86: Further clarify the logic and comments for toggling log dirty
Add a sanity check in kvm_mmu_slot_apply_flags to assert that the
LOG_DIRTY_PAGES flag is indeed being toggled, and explicitly rely on
that holding true when zapping collapsible SPTEs. Manipulating the
CPU dirty log (PML) and write-protection also relies on this assertion,
but that's not obvious in the current code.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210213005015.1651772-11-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kvm/x86.c | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index e89fe98a0099..c0d22f19aed0 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -10761,13 +10761,21 @@ static void kvm_mmu_slot_apply_flags(struct kvm *kvm, enum kvm_mr_change change) { /* - * Nothing to do for RO slots or CREATE/MOVE/DELETE of a slot. - * See comments below. + * Nothing to do for RO slots (which can't be dirtied and can't be made + * writable) or CREATE/MOVE/DELETE of a slot. See comments below. */ if ((change != KVM_MR_FLAGS_ONLY) || (new->flags & KVM_MEM_READONLY)) return; /* + * READONLY and non-flags changes were filtered out above, and the only + * other flag is LOG_DIRTY_PAGES, i.e. something is wrong if dirty + * logging isn't being toggled on or off. + */ + if (WARN_ON_ONCE(!((old->flags ^ new->flags) & KVM_MEM_LOG_DIRTY_PAGES))) + return; + + /* * Dirty logging tracks sptes in 4k granularity, meaning that large * sptes have to be split. If live migration is successful, the guest * in the source machine will be destroyed and large sptes will be @@ -10784,8 +10792,7 @@ static void kvm_mmu_slot_apply_flags(struct kvm *kvm, * MOVE/DELETE: The old mappings will already have been cleaned up by * kvm_arch_flush_shadow_memslot() */ - if ((old->flags & KVM_MEM_LOG_DIRTY_PAGES) && - !(new->flags & KVM_MEM_LOG_DIRTY_PAGES)) + if (!(new->flags & KVM_MEM_LOG_DIRTY_PAGES)) kvm_mmu_zap_collapsible_sptes(kvm, new); /* |