Adds mutex guard to the VMSA updating code. Also adds a check to skip a vCPU if it has already been LAUNCH_UPDATE_VMSA'd which should allow userspace to retry this ioctl until all the vCPUs can be successfully LAUNCH_UPDATE_VMSA'd. Because this operation cannot be undone we cannot unwind if one vCPU fails.
Fixes: ad73109ae7ec ("KVM: SVM: Provide support to launch and run an SEV-ES guest")
Signed-off-by: Peter Gonda pgonda@google.com Cc: Marc Orr marcorr@google.com Cc: Paolo Bonzini pbonzini@redhat.com Cc: Sean Christopherson seanjc@google.com Cc: Brijesh Singh brijesh.singh@amd.com Cc: kvm@vger.kernel.org Cc: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org --- arch/x86/kvm/svm/sev.c | 24 +++++++++++++++++++----- 1 file changed, 19 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 75e0b21ad07c..9a2ebd0328ca 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -598,22 +598,29 @@ static int sev_es_sync_vmsa(struct vcpu_svm *svm) static int sev_launch_update_vmsa(struct kvm *kvm, struct kvm_sev_cmd *argp) { struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; - struct sev_data_launch_update_vmsa vmsa; + struct sev_data_launch_update_vmsa vmsa = {0}; 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);
+ ret = mutex_lock_killable(&vcpu->mutex); + if (ret) + goto out_unlock; + + /* Skip to the next vCPU if this one has already be updated. */ + ret = sev_es_sync_vmsa(svm); + if (svm->vcpu.arch.guest_state_protected) + goto unlock; + /* Perform some pre-encryption checks against the VMSA */ ret = sev_es_sync_vmsa(svm); if (ret) - return ret; + goto out_unlock;
/* * The LAUNCH_UPDATE_VMSA command will perform in-place @@ -629,12 +636,19 @@ static int sev_launch_update_vmsa(struct kvm *kvm, struct kvm_sev_cmd *argp) ret = sev_issue_cmd(kvm, SEV_CMD_LAUNCH_UPDATE_VMSA, &vmsa, &argp->error); if (ret) - return ret; + goto out_unlock;
svm->vcpu.arch.guest_state_protected = true; + +unlock: + mutex_unlock(&vcpu->mutex); }
return 0; + +out_unlock: + mutex_unlock(&vcpu->mutex); + return ret; }
static int sev_launch_measure(struct kvm *kvm, struct kvm_sev_cmd *argp)