KVM: x86/mmu: Set disallowed_nx_huge_page in TDP MMU before setting SPTE

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Set nx_huge_page_disallowed in TDP MMU shadow pages before making the SP
visible to other readers, i.e. before setting its SPTE.  This will allow
KVM to query the flag when determining if a shadow page can be replaced
by a NX huge page without violating the rules of the mitigation.

Note, the shadow/legacy MMU holds mmu_lock for write, so it's impossible
for another CPU to see a shadow page without an up-to-date
nx_huge_page_disallowed, i.e. only the TDP MMU needs the complicated
dance.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: David Matlack <dmatlack@google.com>
Reviewed-by: Yan Zhao <yan.y.zhao@intel.com>
Message-Id: <20221019165618.927057-5-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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Sean Christopherson 2022-10-19 16:56:14 +00:00 • committed by Paolo Bonzini

parent b5b0977f4a

commit 61f9447854

3 changed files with 39 additions and 25 deletions

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28

arch/x86/kvm/mmu/mmu.c

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5

arch/x86/kvm/mmu/mmu_internal.h

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31

arch/x86/kvm/mmu/tdp_mmu.c

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