Commit 58298b06 authored Feb 26, 2022 by Sean Christopherson Committed by Paolo Bonzini Mar 08, 2022

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



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>

parent efd995da

arch/x86/kvm/mmu/tdp_mmu.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -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;
		}