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KVM: x86/mmu: Check for a REMOVED leaf SPTE before making the SPTE

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Explicitly check for a REMOVED leaf SPTE prior to attempting to map
the final SPTE when handling a TDP MMU fault.  Functionally, this is a
nop as tdp_mmu_set_spte_atomic() will eventually detect the frozen SPTE.
Pre-checking for a REMOVED SPTE is a minor optmization, but the real goal
is to allow tdp_mmu_set_spte_atomic() to have an invariant that the "old"
SPTE is never a REMOVED SPTE.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Ben Gardon <bgardon@google.com>
Message-Id: <20220226001546.360188-24-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2022-02-26 00:15:41 +00:00 committed by Paolo Bonzini
parent efd995dae5
commit 58298b0681
1 changed files with 5 additions and 1 deletions
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6
arch/x86/kvm/mmu/tdp_mmu.c
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@ -1193,7 +1193,11 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
}
}
if (iter.level != fault->goal_level) {
/*
* Force the guest to retry the access if the upper level SPTEs aren't
* in place, or if the target leaf SPTE is frozen by another CPU.
*/
if (iter.level != fault->goal_level || is_removed_spte(iter.old_spte)) {
rcu_read_unlock();
return RET_PF_RETRY;
}