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authorSean Christopherson <seanjc@google.com>2021-08-03 09:27:46 -0700
committerPaolo Bonzini <pbonzini@redhat.com>2021-08-04 06:02:09 -0400
commit179c6c27bf487273652efc99acd3ba512a23c137 (patch)
tree7b5458bf5538f72413a38387fbd256e7021bd51d /arch
parent85cd39af14f498f791d8aab3fbd64cd175787f1a (diff)
KVM: SVM: Fix off-by-one indexing when nullifying last used SEV VMCB
Use the raw ASID, not ASID-1, when nullifying the last used VMCB when freeing an SEV ASID. The consumer, pre_sev_run(), indexes the array by the raw ASID, thus KVM could get a false negative when checking for a different VMCB if KVM manages to reallocate the same ASID+VMCB combo for a new VM. Note, this cannot cause a functional issue _in the current code_, as pre_sev_run() also checks which pCPU last did VMRUN for the vCPU, and last_vmentry_cpu is initialized to -1 during vCPU creation, i.e. is guaranteed to mismatch on the first VMRUN. However, prior to commit 8a14fe4f0c54 ("kvm: x86: Move last_cpu into kvm_vcpu_arch as last_vmentry_cpu"), SVM tracked pCPU on its own and zero-initialized the last_cpu variable. Thus it's theoretically possible that older versions of KVM could miss a TLB flush if the first VMRUN is on pCPU0 and the ASID and VMCB exactly match those of a prior VM. Fixes: 70cd94e60c73 ("KVM: SVM: VMRUN should use associated ASID when SEV is enabled") Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: Brijesh Singh <brijesh.singh@amd.com> Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/svm/sev.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 6710d9ee2e4b..4d0aba185412 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -189,7 +189,7 @@ static void sev_asid_free(struct kvm_sev_info *sev)
for_each_possible_cpu(cpu) {
sd = per_cpu(svm_data, cpu);
- sd->sev_vmcbs[pos] = NULL;
+ sd->sev_vmcbs[sev->asid] = NULL;
}
mutex_unlock(&sev_bitmap_lock);