Re: [PATCH V2] KVM: SEV: Acquire vcpu mutex when updating VMSA

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On 15/09/21 19:17, Peter Gonda wrote:
Adds vcpu mutex guard to the VMSA updating code. Refactors out
__sev_launch_update_vmsa() function to deal with per vCPU parts
of sev_launch_update_vmsa().

Fixes: ad73109ae7ec ("KVM: SVM: Provide support to launch and run an SEV-ES guest")

Signed-off-by: Peter Gonda <pgonda@xxxxxxxxxx>
Cc: Marc Orr <marcorr@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
Cc: Brijesh Singh <brijesh.singh@xxxxxxx>
Cc: kvm@xxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---

V2
  * Refactor per vcpu work to separate function.
  * Remove check to skip already initialized VMSAs.
  * Removed vmsa struct zeroing.

---
  arch/x86/kvm/svm/sev.c | 53 ++++++++++++++++++++++++------------------
  1 file changed, 30 insertions(+), 23 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 75e0b21ad07c..766510fe3abb 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -595,43 +595,50 @@ static int sev_es_sync_vmsa(struct vcpu_svm *svm)
  	return 0;
  }
-static int sev_launch_update_vmsa(struct kvm *kvm, struct kvm_sev_cmd *argp)
+static int __sev_launch_update_vmsa(struct kvm *kvm, struct kvm_vcpu *vcpu,
+				    int *error)
  {
-	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
  	struct sev_data_launch_update_vmsa vmsa;
+	struct vcpu_svm *svm = to_svm(vcpu);
+	int ret;
+
+	/* Perform some pre-encryption checks against the VMSA */
+	ret = sev_es_sync_vmsa(svm);
+	if (ret)
+		return ret;
+
+	/*
+	 * The LAUNCH_UPDATE_VMSA command will perform in-place encryption of
+	 * the VMSA memory content (i.e it will write the same memory region
+	 * with the guest's key), so invalidate it first.
+	 */
+	clflush_cache_range(svm->vmsa, PAGE_SIZE);
+
+	vmsa.reserved = 0;
+	vmsa.handle = to_kvm_svm(kvm)->sev_info.handle;
+	vmsa.address = __sme_pa(svm->vmsa);
+	vmsa.len = PAGE_SIZE;
+	return sev_issue_cmd(kvm, SEV_CMD_LAUNCH_UPDATE_VMSA, &vmsa, error);
+}
+
+static int sev_launch_update_vmsa(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
  	struct kvm_vcpu *vcpu;
  	int i, ret;
if (!sev_es_guest(kvm))
  		return -ENOTTY;
- vmsa.reserved = 0;
-
-	kvm_for_each_vcpu(i, vcpu, kvm) {
-		struct vcpu_svm *svm = to_svm(vcpu);
-
-		/* Perform some pre-encryption checks against the VMSA */
-		ret = sev_es_sync_vmsa(svm);
+	kvm_for_each_vcpu(i, vcpu, kvm) {
+		ret = mutex_lock_killable(&vcpu->mutex);
  		if (ret)
  			return ret;
- /*
-		 * The LAUNCH_UPDATE_VMSA command will perform in-place
-		 * encryption of the VMSA memory content (i.e it will write
-		 * the same memory region with the guest's key), so invalidate
-		 * it first.
-		 */
-		clflush_cache_range(svm->vmsa, PAGE_SIZE);
+		ret = __sev_launch_update_vmsa(kvm, vcpu, &argp->error);
- vmsa.handle = sev->handle;
-		vmsa.address = __sme_pa(svm->vmsa);
-		vmsa.len = PAGE_SIZE;
-		ret = sev_issue_cmd(kvm, SEV_CMD_LAUNCH_UPDATE_VMSA, &vmsa,
-				    &argp->error);
+		mutex_unlock(&vcpu->mutex);
  		if (ret)
  			return ret;
-
-		svm->vcpu.arch.guest_state_protected = true;
  	}
return 0;


Queued, thanks.

Paolo




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