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Date: Mon, 4 Jan 2021 09:17:49 -0600
From: Brijesh Singh <brijesh.singh@....com>
To: kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Brijesh Singh <brijesh.singh@....com>,
James Bottomley <jejb@...ux.ibm.com>,
Tom Lendacky <Thomas.Lendacky@....com>,
David Rientjes <rientjes@...gle.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Sean Christopherson <seanjc@...gle.com>,
Borislav Petkov <bp@...en8.de>,
John Allen <john.allen@....com>,
Herbert Xu <herbert@...dor.apana.org.au>,
linux-crypto@...r.kernel.org
Subject: [PATCH v2] KVM/SVM: add support for SEV attestation command
The SEV FW version >= 0.23 added a new command that can be used to query
the attestation report containing the SHA-256 digest of the guest memory
encrypted through the KVM_SEV_LAUNCH_UPDATE_{DATA, VMSA} commands and
sign the report with the Platform Endorsement Key (PEK).
See the SEV FW API spec section 6.8 for more details.
Note there already exist a command (KVM_SEV_LAUNCH_MEASURE) that can be
used to get the SHA-256 digest. The main difference between the
KVM_SEV_LAUNCH_MEASURE and KVM_SEV_ATTESTATION_REPORT is that the latter
can be called while the guest is running and the measurement value is
signed with PEK.
Cc: James Bottomley <jejb@...ux.ibm.com>
Cc: Tom Lendacky <Thomas.Lendacky@....com>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Sean Christopherson <seanjc@...gle.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: John Allen <john.allen@....com>
Cc: Herbert Xu <herbert@...dor.apana.org.au>
Cc: linux-crypto@...r.kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
Acked-by: David Rientjes <rientjes@...gle.com>
Tested-by: James Bottomley <jejb@...ux.ibm.com>
Signed-off-by: Brijesh Singh <brijesh.singh@....com>
---
v2:
* Fix documentation typo
.../virt/kvm/amd-memory-encryption.rst | 21 ++++++
arch/x86/kvm/svm/sev.c | 71 +++++++++++++++++++
drivers/crypto/ccp/sev-dev.c | 1 +
include/linux/psp-sev.h | 17 +++++
include/uapi/linux/kvm.h | 8 +++
5 files changed, 118 insertions(+)
diff --git a/Documentation/virt/kvm/amd-memory-encryption.rst b/Documentation/virt/kvm/amd-memory-encryption.rst
index 09a8f2a34e39..469a6308765b 100644
--- a/Documentation/virt/kvm/amd-memory-encryption.rst
+++ b/Documentation/virt/kvm/amd-memory-encryption.rst
@@ -263,6 +263,27 @@ Returns: 0 on success, -negative on error
__u32 trans_len;
};
+10. KVM_SEV_GET_ATTESTATION_REPORT
+----------------------------------
+
+The KVM_SEV_GET_ATTESTATION_REPORT command can be used by the hypervisor to query the attestation
+report containing the SHA-256 digest of the guest memory and VMSA passed through the KVM_SEV_LAUNCH
+commands and signed with the PEK. The digest returned by the command should match the digest
+used by the guest owner with the KVM_SEV_LAUNCH_MEASURE.
+
+Parameters (in): struct kvm_sev_attestation
+
+Returns: 0 on success, -negative on error
+
+::
+
+ struct kvm_sev_attestation_report {
+ __u8 mnonce[16]; /* A random mnonce that will be placed in the report */
+
+ __u64 uaddr; /* userspace address where the report should be copied */
+ __u32 len;
+ };
+
References
==========
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 566f4d18185b..c4d3ee6be362 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -927,6 +927,74 @@ static int sev_launch_secret(struct kvm *kvm, struct kvm_sev_cmd *argp)
return ret;
}
+static int sev_get_attestation_report(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+ void __user *report = (void __user *)(uintptr_t)argp->data;
+ struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+ struct sev_data_attestation_report *data;
+ struct kvm_sev_attestation_report params;
+ void __user *p;
+ void *blob = NULL;
+ int ret;
+
+ if (!sev_guest(kvm))
+ return -ENOTTY;
+
+ if (copy_from_user(¶ms, (void __user *)(uintptr_t)argp->data, sizeof(params)))
+ return -EFAULT;
+
+ data = kzalloc(sizeof(*data), GFP_KERNEL_ACCOUNT);
+ if (!data)
+ return -ENOMEM;
+
+ /* User wants to query the blob length */
+ if (!params.len)
+ goto cmd;
+
+ p = (void __user *)(uintptr_t)params.uaddr;
+ if (p) {
+ if (params.len > SEV_FW_BLOB_MAX_SIZE) {
+ ret = -EINVAL;
+ goto e_free;
+ }
+
+ ret = -ENOMEM;
+ blob = kmalloc(params.len, GFP_KERNEL);
+ if (!blob)
+ goto e_free;
+
+ data->address = __psp_pa(blob);
+ data->len = params.len;
+ memcpy(data->mnonce, params.mnonce, sizeof(params.mnonce));
+ }
+cmd:
+ data->handle = sev->handle;
+ ret = sev_issue_cmd(kvm, SEV_CMD_ATTESTATION_REPORT, data, &argp->error);
+ /*
+ * If we query the session length, FW responded with expected data.
+ */
+ if (!params.len)
+ goto done;
+
+ if (ret)
+ goto e_free_blob;
+
+ if (blob) {
+ if (copy_to_user(p, blob, params.len))
+ ret = -EFAULT;
+ }
+
+done:
+ params.len = data->len;
+ if (copy_to_user(report, ¶ms, sizeof(params)))
+ ret = -EFAULT;
+e_free_blob:
+ kfree(blob);
+e_free:
+ kfree(data);
+ return ret;
+}
+
int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
{
struct kvm_sev_cmd sev_cmd;
@@ -971,6 +1039,9 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
case KVM_SEV_LAUNCH_SECRET:
r = sev_launch_secret(kvm, &sev_cmd);
break;
+ case KVM_SEV_GET_ATTESTATION_REPORT:
+ r = sev_get_attestation_report(kvm, &sev_cmd);
+ break;
default:
r = -EINVAL;
goto out;
diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 476113e12489..cb9b4c4e371e 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -128,6 +128,7 @@ static int sev_cmd_buffer_len(int cmd)
case SEV_CMD_LAUNCH_UPDATE_SECRET: return sizeof(struct sev_data_launch_secret);
case SEV_CMD_DOWNLOAD_FIRMWARE: return sizeof(struct sev_data_download_firmware);
case SEV_CMD_GET_ID: return sizeof(struct sev_data_get_id);
+ case SEV_CMD_ATTESTATION_REPORT: return sizeof(struct sev_data_attestation_report);
default: return 0;
}
diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
index 49d155cd2dfe..b801ead1e2bb 100644
--- a/include/linux/psp-sev.h
+++ b/include/linux/psp-sev.h
@@ -66,6 +66,7 @@ enum sev_cmd {
SEV_CMD_LAUNCH_MEASURE = 0x033,
SEV_CMD_LAUNCH_UPDATE_SECRET = 0x034,
SEV_CMD_LAUNCH_FINISH = 0x035,
+ SEV_CMD_ATTESTATION_REPORT = 0x036,
/* Guest migration commands (outgoing) */
SEV_CMD_SEND_START = 0x040,
@@ -483,6 +484,22 @@ struct sev_data_dbg {
u32 len; /* In */
} __packed;
+/**
+ * struct sev_data_attestation_report - SEV_ATTESTATION_REPORT command parameters
+ *
+ * @handle: handle of the VM
+ * @mnonce: a random nonce that will be included in the report.
+ * @address: physical address where the report will be copied.
+ * @len: length of the physical buffer.
+ */
+struct sev_data_attestation_report {
+ u32 handle; /* In */
+ u32 reserved;
+ u64 address; /* In */
+ u8 mnonce[16]; /* In */
+ u32 len; /* In/Out */
+} __packed;
+
#ifdef CONFIG_CRYPTO_DEV_SP_PSP
/**
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index ca41220b40b8..d3385f7f08a2 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1585,6 +1585,8 @@ enum sev_cmd_id {
KVM_SEV_DBG_ENCRYPT,
/* Guest certificates commands */
KVM_SEV_CERT_EXPORT,
+ /* Attestation report */
+ KVM_SEV_GET_ATTESTATION_REPORT,
KVM_SEV_NR_MAX,
};
@@ -1637,6 +1639,12 @@ struct kvm_sev_dbg {
__u32 len;
};
+struct kvm_sev_attestation_report {
+ __u8 mnonce[16];
+ __u64 uaddr;
+ __u32 len;
+};
+
#define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0)
#define KVM_DEV_ASSIGN_PCI_2_3 (1 << 1)
#define KVM_DEV_ASSIGN_MASK_INTX (1 << 2)
--
2.17.1
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