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KVM: x86/mmu: Reword a misleading comment about checking gpte_changed()

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Rewrite the comment in FNAME(fetch) to explain why KVM needs to check that
the gPTE is still fresh before continuing the shadow page walk, even if
KVM already has a linked shadow page for the gPTE in question.

No functional change intended.

Link: https://lore.kernel.org/r/20240802203900.348808-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson
2024-08-02 13:39:00 -07:00
parent 7d67b03e6f
commit 1dc9cc1c4c
1 changed files with 8 additions and 2 deletions
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10
arch/x86/kvm/mmu/paging_tmpl.h
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@@ -695,8 +695,14 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
return RET_PF_RETRY;
/*
* Verify that the gpte in the page we've just write
* protected is still there.
* Verify that the gpte in the page, which is now either
* write-protected or unsync, wasn't modified between the fault
* and acquiring mmu_lock. This needs to be done even when
* reusing an existing shadow page to ensure the information
* gathered by the walker matches the information stored in the
* shadow page (which could have been modified by a different
* vCPU even if the page was already linked). Holding mmu_lock
* prevents the shadow page from changing after this point.
*/
if (FNAME(gpte_changed)(vcpu, gw, it.level - 1))
return RET_PF_RETRY;