Re: [PATCH v2 0/6] KVM: x86: Apply NX mitigation more precisely

Mingwei Zhang
2022-07-26T05:37:29Z

On Sat, Jul 23, 2022, 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.

hmm, I applied this patch set (v2) on top of kvm/queue (HEAD:
1a4d88a361af) and it seems kvm-unit-tests/vmx failed on both ept=1 and
ept=0. And it did not work on our internel kernel either (kernel
crashed).

Maybe there is still minor issues?

>
> 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
>
> arch/x86/include/asm/kvm_host.h | 17 ++---
> arch/x86/kvm/mmu/mmu.c | 107 ++++++++++++++++++++++----------
> arch/x86/kvm/mmu/mmu_internal.h | 41 +++++++-----
> arch/x86/kvm/mmu/paging_tmpl.h | 6 +-
> arch/x86/kvm/mmu/spte.c | 11 ++++
> arch/x86/kvm/mmu/spte.h | 17 +++++
> arch/x86/kvm/mmu/tdp_mmu.c | 49 +++++++++------
> arch/x86/kvm/mmu/tdp_mmu.h | 2 +
> 8 files changed, 167 insertions(+), 83 deletions(-)
>
>
> base-commit: 1a4d88a361af4f2e91861d632c6a1fe87a9665c2
> --
> 2.37.1.359.gd136c6c3e2-goog
>