Commit 2c07ded0 authored by Brijesh Singh's avatar Brijesh Singh Committed by Paolo Bonzini
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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@linux.ibm.com>
Cc: Tom Lendacky <Thomas.Lendacky@amd.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: John Allen <john.allen@amd.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: linux-crypto@vger.kernel.org
Reviewed-by: default avatarTom Lendacky <thomas.lendacky@amd.com>
Acked-by: default avatarDavid Rientjes <rientjes@google.com>
Tested-by: default avatarJames Bottomley <jejb@linux.ibm.com>
Signed-off-by: default avatarBrijesh Singh <brijesh.singh@amd.com>
Message-Id: <20210104151749.30248-1-brijesh.singh@amd.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent c1d1650f

Documentation/virt/kvm/amd-memory-encryption.rst

+21 −0
Original line number Diff line number Diff line
@@ -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

==========

arch/x86/kvm/svm/sev.c

+71 −0
Original line number Diff line number Diff line
@@ -1041,6 +1041,74 @@ 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(&params, (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, &params, 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;
@@ -1091,6 +1159,9 @@ 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;

drivers/crypto/ccp/sev-dev.c

+1 −0
Original line number Diff line number Diff line
@@ -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;

	}

include/linux/psp-sev.h

+17 −0
Original line number Diff line number Diff line
@@ -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



/**

include/uapi/linux/kvm.h

+8 −0
Original line number Diff line number Diff line
@@ -1593,6 +1593,8 @@ 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,

};
@@ -1645,6 +1647,12 @@ 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)