Re: [PATCH Part2 v6 47/49] *fix for stale per-cpu pointer due to cond_resched during ghcb mapping
From: Peter Gonda <hidden>
Date: 2022-06-24 16:36:17
Also in:
kvm, linux-crypto, linux-mm, lkml
On Mon, Jun 20, 2022 at 5:15 PM Ashish Kalra [off-list ref] wrote:
From: Michael Roth <redacted> Signed-off-by: Michael Roth <redacted>
Can you add a commit description here? Is this a fix for existing SEV-ES support or should this be incorporated into a patch in this series which adds this issue?
quoted hunk ↗ jump to hunk
--- arch/x86/kvm/svm/svm.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index fced6ea423ad..f78e3b1bde0e 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c@@ -1352,7 +1352,7 @@ static void svm_vcpu_free(struct kvm_vcpu *vcpu) static void svm_prepare_switch_to_guest(struct kvm_vcpu *vcpu) { struct vcpu_svm *svm = to_svm(vcpu); - struct svm_cpu_data *sd = per_cpu(svm_data, vcpu->cpu); + struct svm_cpu_data *sd; if (sev_es_guest(vcpu->kvm)) sev_es_unmap_ghcb(svm);@@ -1360,6 +1360,10 @@ static void svm_prepare_switch_to_guest(struct kvm_vcpu *vcpu) if (svm->guest_state_loaded) return; + /* sev_es_unmap_ghcb() can resched, so grab per-cpu pointer afterward. */ + barrier(); + sd = per_cpu(svm_data, vcpu->cpu); + /* * Save additional host state that will be restored on VMEXIT (sev-es) * or subsequent vmload of host save area. --2.25.1