Messages in this thread | | | Date | Wed, 13 Mar 2024 16:55:04 +0800 | From | Yan Zhao <> | Subject | Re: [PATCH 5/5] KVM: VMX: Always honor guest PAT on CPUs that support self-snoop |
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> We'll certain fix the security hole on CPUs w/ self-snoop. In this case > CPU accesses are guaranteed to be coherent and the vulnerability can > only be exposed via non-coherent DMA which is supposed to be fixed > by your coming series. > > But for old CPUs w/o self-snoop the hole can be exploited using either CPU > or non-coherent DMA once the guest PAT is honored. As long as nobody > is willing to actually fix the CPU path (is it possible?) I'm kind of convinced We can cook a patch to check CPU self-snoop and force WB in EPT even for non-coherent DMA if no self-snoop. Then back porting such a patch together with the IOMMU side mitigation for non-coherent DMA.
Otherwise, IOMMU side mitigation alone is meaningless for platforms of CPU of no self-snoop.
> by Sean that sustaining the old behavior is probably the best option... Yes, as long as we think exposing secuirty hole on those platforms is acceptable.
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