KVM: x86/mmu: Check SPTE writable invariants when setting leaf SPTEs

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Check SPTE writable invariants when setting SPTEs rather than in
spte_can_locklessly_be_made_writable(). By the time KVM checks
spte_can_locklessly_be_made_writable(), the SPTE has long been since
corrupted.

Note that these invariants only apply to shadow-present leaf SPTEs (i.e.
not to MMIO SPTEs, non-leaf SPTEs, etc.). Add a comment explaining the
restriction and only instrument the code paths that set shadow-present
leaf SPTEs.

To account for access tracking, also check the SPTE writable invariants
when marking an SPTE as an access track SPTE. This also lets us remove
a redundant WARN from mark_spte_for_access_track().

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20220125230518.1697048-3-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

...

This commit is contained in:

David Matlack 2022-01-25 23:05:15 +00:00 • committed by Paolo Bonzini

parent 932859a4e0

commit 115111efd9

4 changed files with 6 additions and 9 deletions

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1

arch/x86/kvm/mmu/mmu.c

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9

arch/x86/kvm/mmu/spte.c

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2

arch/x86/kvm/mmu/spte.h

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3

arch/x86/kvm/mmu/tdp_mmu.c

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