virt: sevguest: Add support to get extended report (d80b494f) · Commits · github.com / kvm-riscv / linux

Documentation/virt/coco/sevguest.rst

+23 −0

Original line number	Diff line number	Diff line
		@@ -95,6 +95,29 @@ on the various fields passed in the key derivation request.
		On success, the snp_derived_key_resp.data contains the derived key value. See
		the SEV-SNP specification for further details.


		2.3 SNP_GET_EXT_REPORT
		----------------------
		:Technology: sev-snp
		:Type: guest ioctl
		:Parameters (in/out): struct snp_ext_report_req
		:Returns (out): struct snp_report_resp on success, -negative on error

		The SNP_GET_EXT_REPORT ioctl is similar to the SNP_GET_REPORT. The difference is
		related to the additional certificate data that is returned with the report.
		The certificate data returned is being provided by the hypervisor through the
		SNP_SET_EXT_CONFIG.

		The ioctl uses the SNP_GUEST_REQUEST (MSG_REPORT_REQ) command provided by the SEV-SNP
		firmware to get the attestation report.

		On success, the snp_ext_report_resp.data will contain the attestation report
		and snp_ext_report_req.certs_address will contain the certificate blob. If the
		length of the blob is smaller than expected then snp_ext_report_req.certs_len will
		be updated with the expected value.

		See GHCB specification for further detail on how to parse the certificate blob.

		Reference
		---------

drivers/virt/coco/sevguest/sevguest.c

+90 −2

Original line number	Diff line number	Diff line
		@@ -43,6 +43,7 @@ struct snp_guest_dev {
		struct device *dev;
		struct miscdevice misc;

		void *certs_data;
		struct snp_guest_crypto *crypto;
		struct snp_guest_msg request, response;
		struct snp_secrets_page_layout *layout;
		@@ -433,6 +434,82 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque
		return rc;
		}

		static int get_ext_report(struct snp_guest_dev snp_dev, struct snp_guest_request_ioctl arg)
		{
		struct snp_guest_crypto *crypto = snp_dev->crypto;
		struct snp_ext_report_req req;
		struct snp_report_resp *resp;
		int ret, npages = 0, resp_len;

		lockdep_assert_held(&snp_cmd_mutex);

		if (!arg->req_data \|\| !arg->resp_data)
		return -EINVAL;

		if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
		return -EFAULT;

		/* userspace does not want certificate data */
		if (!req.certs_len \|\| !req.certs_address)
		goto cmd;

		if (req.certs_len > SEV_FW_BLOB_MAX_SIZE \|\|
		!IS_ALIGNED(req.certs_len, PAGE_SIZE))
		return -EINVAL;

		if (!access_ok((const void __user *)req.certs_address, req.certs_len))
		return -EFAULT;

		/*
		* Initialize the intermediate buffer with all zeros. This buffer
		* is used in the guest request message to get the certs blob from
		* the host. If host does not supply any certs in it, then copy
		* zeros to indicate that certificate data was not provided.
		*/
		memset(snp_dev->certs_data, 0, req.certs_len);
		npages = req.certs_len >> PAGE_SHIFT;
		cmd:
		/*
		* The intermediate response buffer is used while decrypting the
		* response payload. Make sure that it has enough space to cover the
		* authtag.
		*/
		resp_len = sizeof(resp->data) + crypto->a_len;
		resp = kzalloc(resp_len, GFP_KERNEL_ACCOUNT);
		if (!resp)
		return -ENOMEM;

		snp_dev->input.data_npages = npages;
		ret = handle_guest_request(snp_dev, SVM_VMGEXIT_EXT_GUEST_REQUEST, arg->msg_version,
		SNP_MSG_REPORT_REQ, &req.data,
		sizeof(req.data), resp->data, resp_len, &arg->fw_err);

		/* If certs length is invalid then copy the returned length */
		if (arg->fw_err == SNP_GUEST_REQ_INVALID_LEN) {
		req.certs_len = snp_dev->input.data_npages << PAGE_SHIFT;

		if (copy_to_user((void __user *)arg->req_data, &req, sizeof(req)))
		ret = -EFAULT;
		}

		if (ret)
		goto e_free;

		if (npages &&
		copy_to_user((void __user *)req.certs_address, snp_dev->certs_data,
		req.certs_len)) {
		ret = -EFAULT;
		goto e_free;
		}

		if (copy_to_user((void __user )arg->resp_data, resp, sizeof(resp)))
		ret = -EFAULT;

		e_free:
		kfree(resp);
		return ret;
		}

		static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
		{
		struct snp_guest_dev *snp_dev = to_snp_dev(file);
		@@ -465,6 +542,9 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long
		case SNP_GET_DERIVED_KEY:
		ret = get_derived_key(snp_dev, &input);
		break;
		case SNP_GET_EXT_REPORT:
		ret = get_ext_report(snp_dev, &input);
		break;
		default:
		break;
		}
		@@ -595,10 +675,14 @@ static int __init snp_guest_probe(struct platform_device *pdev)
		if (!snp_dev->response)
		goto e_free_request;

		snp_dev->certs_data = alloc_shared_pages(SEV_FW_BLOB_MAX_SIZE);
		if (!snp_dev->certs_data)
		goto e_free_response;

		ret = -EIO;
		snp_dev->crypto = init_crypto(snp_dev, snp_dev->vmpck, VMPCK_KEY_LEN);
		if (!snp_dev->crypto)
		goto e_free_response;
		goto e_free_cert_data;

		misc = &snp_dev->misc;
		misc->minor = MISC_DYNAMIC_MINOR;
		@@ -608,14 +692,17 @@ static int __init snp_guest_probe(struct platform_device *pdev)
		/* initial the input address for guest request */
		snp_dev->input.req_gpa = __pa(snp_dev->request);
		snp_dev->input.resp_gpa = __pa(snp_dev->response);
		snp_dev->input.data_gpa = __pa(snp_dev->certs_data);

		ret = misc_register(misc);
		if (ret)
		goto e_free_response;
		goto e_free_cert_data;

		dev_info(dev, "Initialized SNP guest driver (using vmpck_id %d)\n", vmpck_id);
		return 0;

		e_free_cert_data:
		free_shared_pages(snp_dev->certs_data, SEV_FW_BLOB_MAX_SIZE);
		e_free_response:
		free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
		e_free_request:
		@@ -629,6 +716,7 @@ static int __exit snp_guest_remove(struct platform_device *pdev)
		{
		struct snp_guest_dev *snp_dev = platform_get_drvdata(pdev);

		free_shared_pages(snp_dev->certs_data, SEV_FW_BLOB_MAX_SIZE);
		free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
		free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
		deinit_crypto(snp_dev->crypto);

include/uapi/linux/sev-guest.h

+13 −0

Original line number	Diff line number	Diff line
		@@ -56,6 +56,16 @@ struct snp_guest_request_ioctl {
		__u64 fw_err;
		};

		struct snp_ext_report_req {
		struct snp_report_req data;

		/* where to copy the certificate blob */
		__u64 certs_address;

		/* length of the certificate blob */
		__u32 certs_len;
		};

		#define SNP_GUEST_REQ_IOC_TYPE 'S'

		/* Get SNP attestation report */
		@@ -64,4 +74,7 @@ struct snp_guest_request_ioctl {
		/* Get a derived key from the root */
		#define SNP_GET_DERIVED_KEY _IOWR(SNP_GUEST_REQ_IOC_TYPE, 0x1, struct snp_guest_request_ioctl)

		/* Get SNP extended report as defined in the GHCB specification version 2. */
		#define SNP_GET_EXT_REPORT _IOWR(SNP_GUEST_REQ_IOC_TYPE, 0x2, struct snp_guest_request_ioctl)

		#endif /* __UAPI_LINUX_SEV_GUEST_H_ */