[RFC PATCH v2 31/32] kvm: svm: Add support for SEV LAUNCH_MEASURE command

[Brijesh Singh <brijesh.singh@xxxxxxx>]

The command is used to retrieve the measurement of memory encrypted through
the LAUNCH_UPDATE_DATA command. This measurement can be used for attestation
purposes.

Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
---
 arch/x86/kvm/svm.c |   52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 64899ed..13996d6 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -6141,6 +6141,54 @@ static int sev_dbg_encrypt(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	return ret;
 }
 
+static int sev_launch_measure(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+	int ret;
+	void *addr = NULL;
+	struct kvm_sev_launch_measure params;
+	struct sev_data_launch_measure *data;
+
+	if (!sev_guest(kvm))
+		return -ENOTTY;
+
+	if (copy_from_user(&params, (void *)argp->data,
+				sizeof(struct kvm_sev_launch_measure)))
+		return -EFAULT;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	if (params.address && params.length) {
+		ret = -EFAULT;
+		addr = kzalloc(params.length, GFP_KERNEL);
+		if (!addr)
+			goto err_1;
+		data->address = __psp_pa(addr);
+		data->length = params.length;
+	}
+
+	data->handle = sev_get_handle(kvm);
+	ret = sev_issue_cmd(kvm, SEV_CMD_LAUNCH_MEASURE, data, &argp->error);
+
+	/* copy the measurement to userspace */
+	if (addr &&
+		copy_to_user((void *)params.address, addr, params.length)) {
+		ret = -EFAULT;
+		goto err_1;
+	}
+
+	params.length = data->length;
+	if (copy_to_user((void *)argp->data, &params,
+				sizeof(struct kvm_sev_launch_measure)))
+		ret = -EFAULT;
+
+	kfree(addr);
+err_1:
+	kfree(data);
+	return ret;
+}
+
 static int amd_memory_encryption_cmd(struct kvm *kvm, void __user *argp)
 {
 	int r = -ENOTTY;
@@ -6176,6 +6224,10 @@ static int amd_memory_encryption_cmd(struct kvm *kvm, void __user *argp)
 		r = sev_dbg_encrypt(kvm, &sev_cmd);
 		break;
 	}
+	case KVM_SEV_LAUNCH_MEASURE: {
+		r = sev_launch_measure(kvm, &sev_cmd);
+		break;
+	}
 	default:
 		break;
 	}