path: root/virt
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authorSean Christopherson <sean.j.christopherson@intel.com>2019-02-05 13:01:13 -0800
committerPaolo Bonzini <pbonzini@redhat.com>2019-02-20 22:48:33 +0100
commitddfd1730fd829743e41213e32ccc8b4aa6dc8325 (patch)
tree273f1b9ca1d94ceae872b29811359a0c0253e7e1 /virt
parente1359e2beb8b0a1188abc997273acbaedc8ee791 (diff)
KVM: x86/mmu: Do not cache MMIO accesses while memslots are in flux
When installing new memslots, KVM sets bit 0 of the generation number to indicate that an update is in-progress. Until the update is complete, there are no guarantees as to whether a vCPU will see the old or the new memslots. Explicity prevent caching MMIO accesses so as to avoid using an access cached from the old memslots after the new memslots have been installed. Note that it is unclear whether or not disabling caching during the update window is strictly necessary as there is no definitive documentation as to what ordering guarantees KVM provides with respect to updating memslots. That being said, the MMIO spte code does not allow reusing sptes created while an update is in-progress, and the associated documentation explicitly states: We do not want to use an MMIO sptes created with an odd generation number, ... If KVM is unlucky and creates an MMIO spte while the low bit is 1, the next access to the spte will always be a cache miss. At the very least, disabling the per-vCPU MMIO cache during updates will make its behavior consistent with the MMIO spte behavior and documentation. Fixes: 56f17dd3fbc4 ("kvm: x86: fix stale mmio cache bug") Cc: <stable@vger.kernel.org> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'virt')
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