Messages in this thread Patch in this message | | | From | Paolo Bonzini <> | Subject | [PATCH v4 25/30] KVM: x86/mmu: Check for a REMOVED leaf SPTE before making the SPTE | Date | Thu, 3 Mar 2022 14:38:37 -0500 |
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From: Sean Christopherson <seanjc@google.com>
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> --- arch/x86/kvm/mmu/tdp_mmu.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 2456f880508d..89e6eb6640fe 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -1202,7 +1202,11 @@ 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; } -- 2.31.1
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