KVM: x86/mmu: Document and enforce MMU-writable and Host-writable invariants

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SPTEs are tagged with software-only bits to indicate if it is
"MMU-writable" and "Host-writable". These bits are used to determine why
KVM has marked an SPTE as read-only.

Document these bits and their invariants, and enforce the invariants
with new WARNs in spte_can_locklessly_be_made_writable() to ensure they
are not accidentally violated in the future.

Opportunistically move DEFAULT_SPTE_{MMU,HOST}_WRITABLE next to
EPT_SPTE_{MMU,HOST}_WRITABLE since the new documentation applies to
both.

No functional change intended.

Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20220113233020.3986005-4-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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David Matlack 2022-01-13 23:30:19 +00:00 • committed by Paolo Bonzini

parent f082d86ea6

commit 5f16bcac6e

1 changed files with 36 additions and 6 deletions

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arch/x86/kvm/mmu/spte.h

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