Messages in this thread | | | Date | Thu, 28 Jul 2022 22:17:31 +0200 | Subject | Re: [PATCH v2 0/6] KVM: x86: Apply NX mitigation more precisely | From | Paolo Bonzini <> |
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On 7/23/22 03:23, Sean Christopherson wrote: > Patch 6 from Mingwei is the end goal of the series. KVM incorrectly > assumes that the NX huge page mitigation is the only scenario where KVM > will create a non-leaf page instead of a huge page. Precisely track > (via kvm_mmu_page) if a non-huge page is being forced and use that info > to avoid unnecessarily forcing smaller page sizes in > disallowed_hugepage_adjust(). > > v2: Rebase, tweak a changelog accordingly. > > v1:https://lore.kernel.org/all/20220409003847.819686-1-seanjc@google.com > > Mingwei Zhang (1): > KVM: x86/mmu: explicitly check nx_hugepage in > disallowed_hugepage_adjust() > > Sean Christopherson (5): > KVM: x86/mmu: Tag disallowed NX huge pages even if they're not tracked > KVM: x86/mmu: Properly account NX huge page workaround for nonpaging > MMUs > KVM: x86/mmu: Set disallowed_nx_huge_page in TDP MMU before setting > SPTE > KVM: x86/mmu: Track the number of TDP MMU pages, but not the actual > pages > KVM: x86/mmu: Add helper to convert SPTE value to its shadow page
Some of the benefits are cool, such as not having to track the pages for the TDP MMU, and patch 2 is a borderline bugfix, but there's quite a lot of new non-obvious complexity here.
So the obligatory question is: is it worth a hundred lines of new code?
Paolo
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