diff options
| author | Sean Christopherson <sean.j.christopherson@intel.com> | 2019-02-05 12:54:17 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-03-23 14:35:31 +0100 |
| commit | 89dce6e457a14aa53fc0a83ec8f4206748a5c87a (patch) | |
| tree | 45dd84776ede9aca4804f9e10f2cf32b480119a0 /virt/kvm | |
| parent | 1e6e41f5fcddac8a9334009fec068f4f7ec20723 (diff) | |
KVM: Call kvm_arch_memslots_updated() before updating memslots
commit 152482580a1b0accb60676063a1ac57b2d12daf6 upstream.
kvm_arch_memslots_updated() is at this point in time an x86-specific
hook for handling MMIO generation wraparound. x86 stashes 19 bits of
the memslots generation number in its MMIO sptes in order to avoid
full page fault walks for repeat faults on emulated MMIO addresses.
Because only 19 bits are used, wrapping the MMIO generation number is
possible, if unlikely. kvm_arch_memslots_updated() alerts x86 that
the generation has changed so that it can invalidate all MMIO sptes in
case the effective MMIO generation has wrapped so as to avoid using a
stale spte, e.g. a (very) old spte that was created with generation==0.
Given that the purpose of kvm_arch_memslots_updated() is to prevent
consuming stale entries, it needs to be called before the new generation
is propagated to memslots. Invalidating the MMIO sptes after updating
memslots means that there is a window where a vCPU could dereference
the new memslots generation, e.g. 0, and incorrectly reuse an old MMIO
spte that was created with (pre-wrap) generation==0.
Fixes: e59dbe09f8e6 ("KVM: Introduce kvm_arch_memslots_updated()")
Cc: <stable@vger.kernel.org>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'virt/kvm')
| -rw-r--r-- | virt/kvm/arm/mmu.c | 2 | ||||
| -rw-r--r-- | virt/kvm/kvm_main.c | 7 |
2 files changed, 6 insertions, 3 deletions
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c index ec275b8472a9..225dc671ae31 100644 --- a/virt/kvm/arm/mmu.c +++ b/virt/kvm/arm/mmu.c @@ -1955,7 +1955,7 @@ int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot, return 0; } -void kvm_arch_memslots_updated(struct kvm *kvm, struct kvm_memslots *slots) +void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen) { } diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 9b79818758dc..66cc315efa6d 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -856,6 +856,7 @@ static struct kvm_memslots *install_new_memslots(struct kvm *kvm, int as_id, struct kvm_memslots *slots) { struct kvm_memslots *old_memslots = __kvm_memslots(kvm, as_id); + u64 gen; /* * Set the low bit in the generation, which disables SPTE caching @@ -878,9 +879,11 @@ static struct kvm_memslots *install_new_memslots(struct kvm *kvm, * space 0 will use generations 0, 4, 8, ... while * address space 1 will * use generations 2, 6, 10, 14, ... */ - slots->generation += KVM_ADDRESS_SPACE_NUM * 2 - 1; + gen = slots->generation + KVM_ADDRESS_SPACE_NUM * 2 - 1; - kvm_arch_memslots_updated(kvm, slots); + kvm_arch_memslots_updated(kvm, gen); + + slots->generation = gen; return old_memslots; } |