Date:   Wed, 14 Dec 2022 13:40:23 -0600
From:   Michael Roth <michael.roth@....com>
To:     <kvm@...r.kernel.org>
CC:     <linux-coco@...ts.linux.dev>, <linux-mm@...ck.org>,
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        <ashish.kalra@....com>, <harald@...fian.com>,
        Brijesh Singh <brijesh.singh@....com>
Subject: [PATCH RFC v7 31/64] crypto: ccp: Add the SNP_{SET,GET}_EXT_CONFIG command

From: Brijesh Singh <brijesh.singh@....com>

The SEV-SNP firmware provides the SNP_CONFIG command used to set the
system-wide configuration value for SNP guests. The information includes
the TCB version string to be reported in guest attestation reports.

Version 2 of the GHCB specification adds an NAE (SNP extended guest
request) that a guest can use to query the reports that include additional
certificates.

In both cases, userspace provided additional data is included in the
attestation reports. The userspace will use the SNP_SET_EXT_CONFIG
command to give the certificate blob and the reported TCB version string
at once. Note that the specification defines certificate blob with a
specific GUID format; the userspace is responsible for building the
proper certificate blob. The ioctl treats it an opaque blob.

While it is not defined in the spec, but let's add SNP_GET_EXT_CONFIG
command that can be used to obtain the data programmed through the
SNP_SET_EXT_CONFIG.

Signed-off-by: Brijesh Singh <brijesh.singh@....com>
Signed-off-by: Ashish Kalra <ashish.kalra@....com>
Signed-off-by: Michael Roth <michael.roth@....com>
---
 Documentation/virt/coco/sev-guest.rst |  27 ++++++
 drivers/crypto/ccp/sev-dev.c          | 123 ++++++++++++++++++++++++++
 drivers/crypto/ccp/sev-dev.h          |   4 +
 include/uapi/linux/psp-sev.h          |  17 ++++
 4 files changed, 171 insertions(+)

diff --git a/Documentation/virt/coco/sev-guest.rst b/Documentation/virt/coco/sev-guest.rst
index 11ea67c944df..fad1e5639dac 100644
--- a/Documentation/virt/coco/sev-guest.rst
+++ b/Documentation/virt/coco/sev-guest.rst
@@ -145,6 +145,33 @@ The SNP_PLATFORM_STATUS command is used to query the SNP platform status. The
 status includes API major, minor version and more. See the SEV-SNP
 specification for further details.
 
+2.5 SNP_SET_EXT_CONFIG
+----------------------
+:Technology: sev-snp
+:Type: hypervisor ioctl cmd
+:Parameters (in): struct sev_data_snp_ext_config
+:Returns (out): 0 on success, -negative on error
+
+The SNP_SET_EXT_CONFIG is used to set the system-wide configuration such as
+reported TCB version in the attestation report. The command is similar to
+SNP_CONFIG command defined in the SEV-SNP spec. The main difference is the
+command also accepts an additional certificate blob defined in the GHCB
+specification.
+
+If the certs_address is zero, then the previous certificate blob will deleted.
+For more information on the certificate blob layout, see the GHCB spec
+(extended guest request message).
+
+2.6 SNP_GET_EXT_CONFIG
+----------------------
+:Technology: sev-snp
+:Type: hypervisor ioctl cmd
+:Parameters (in): struct sev_data_snp_ext_config
+:Returns (out): 0 on success, -negative on error
+
+The SNP_SET_EXT_CONFIG is used to query the system-wide configuration set
+through the SNP_SET_EXT_CONFIG.
+
 3. SEV-SNP CPUID Enforcement
 ============================
 
diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 10b87ec339aa..d59727ac2bdd 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -1480,6 +1480,10 @@ static int __sev_snp_shutdown_locked(int *error)
 	data.length = sizeof(data);
 	data.iommu_snp_shutdown = 1;
 
+	/* Free the memory used for caching the certificate data */
+	kfree(sev->snp_certs_data);
+	sev->snp_certs_data = NULL;
+
 	wbinvd_on_all_cpus();
 
 retry:
@@ -1792,6 +1796,118 @@ static int sev_ioctl_snp_platform_status(struct sev_issue_cmd *argp)
 	return ret;
 }
 
+static int sev_ioctl_snp_get_config(struct sev_issue_cmd *argp)
+{
+	struct sev_device *sev = psp_master->sev_data;
+	struct sev_user_data_ext_snp_config input;
+	int ret;
+
+	if (!sev->snp_initialized || !argp->data)
+		return -EINVAL;
+
+	memset(&input, 0, sizeof(input));
+
+	if (copy_from_user(&input, (void __user *)argp->data, sizeof(input)))
+		return -EFAULT;
+
+	/* Copy the TCB version programmed through the SET_CONFIG to userspace */
+	if (input.config_address) {
+		if (copy_to_user((void * __user)input.config_address,
+				 &sev->snp_config, sizeof(struct sev_user_data_snp_config)))
+			return -EFAULT;
+	}
+
+	/* Copy the extended certs programmed through the SNP_SET_CONFIG */
+	if (input.certs_address && sev->snp_certs_data) {
+		if (input.certs_len < sev->snp_certs_len) {
+			/* Return the certs length to userspace */
+			input.certs_len = sev->snp_certs_len;
+
+			ret = -ENOSR;
+			goto e_done;
+		}
+
+		if (copy_to_user((void * __user)input.certs_address,
+				 sev->snp_certs_data, sev->snp_certs_len))
+			return -EFAULT;
+	}
+
+	ret = 0;
+
+e_done:
+	if (copy_to_user((void __user *)argp->data, &input, sizeof(input)))
+		ret = -EFAULT;
+
+	return ret;
+}
+
+static int sev_ioctl_snp_set_config(struct sev_issue_cmd *argp, bool writable)
+{
+	struct sev_device *sev = psp_master->sev_data;
+	struct sev_user_data_ext_snp_config input;
+	struct sev_user_data_snp_config config;
+	void *certs = NULL;
+	int ret = 0;
+
+	if (!sev->snp_initialized || !argp->data)
+		return -EINVAL;
+
+	if (!writable)
+		return -EPERM;
+
+	memset(&input, 0, sizeof(input));
+
+	if (copy_from_user(&input, (void __user *)argp->data, sizeof(input)))
+		return -EFAULT;
+
+	/* Copy the certs from userspace */
+	if (input.certs_address) {
+		if (!input.certs_len || !IS_ALIGNED(input.certs_len, PAGE_SIZE))
+			return -EINVAL;
+
+		certs = psp_copy_user_blob(input.certs_address, input.certs_len);
+		if (IS_ERR(certs))
+			return PTR_ERR(certs);
+	}
+
+	/* Issue the PSP command to update the TCB version using the SNP_CONFIG. */
+	if (input.config_address) {
+		memset(&config, 0, sizeof(config));
+		if (copy_from_user(&config,
+				   (void __user *)input.config_address, sizeof(config))) {
+			ret = -EFAULT;
+			goto e_free;
+		}
+
+		ret = __sev_do_cmd_locked(SEV_CMD_SNP_CONFIG, &config, &argp->error);
+		if (ret)
+			goto e_free;
+
+		memcpy(&sev->snp_config, &config, sizeof(config));
+	}
+
+	/*
+	 * If the new certs are passed then cache it else free the old certs.
+	 */
+	mutex_lock(&sev->snp_certs_lock);
+	if (certs) {
+		kfree(sev->snp_certs_data);
+		sev->snp_certs_data = certs;
+		sev->snp_certs_len = input.certs_len;
+	} else {
+		kfree(sev->snp_certs_data);
+		sev->snp_certs_data = NULL;
+		sev->snp_certs_len = 0;
+	}
+	mutex_unlock(&sev->snp_certs_lock);
+
+	return 0;
+
+e_free:
+	kfree(certs);
+	return ret;
+}
+
 static long sev_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
 {
 	void __user *argp = (void __user *)arg;
@@ -1846,6 +1962,12 @@ static long sev_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
 	case SNP_PLATFORM_STATUS:
 		ret = sev_ioctl_snp_platform_status(&input);
 		break;
+	case SNP_SET_EXT_CONFIG:
+		ret = sev_ioctl_snp_set_config(&input, writable);
+		break;
+	case SNP_GET_EXT_CONFIG:
+		ret = sev_ioctl_snp_get_config(&input);
+		break;
 	default:
 		ret = -EINVAL;
 		goto out;
@@ -1961,6 +2083,7 @@ int sev_dev_init(struct psp_device *psp)
 		goto e_sev;
 
 	sev->cmd_buf_backup = (uint8_t *)sev->cmd_buf + PAGE_SIZE;
+	mutex_init(&sev->snp_certs_lock);
 
 	psp->sev_data = sev;
 
diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.h
index 19d79f9d4212..41d5353d5bab 100644
--- a/drivers/crypto/ccp/sev-dev.h
+++ b/drivers/crypto/ccp/sev-dev.h
@@ -66,6 +66,10 @@ struct sev_device {
 
 	bool snp_initialized;
 	struct snp_host_map snp_host_map[MAX_SNP_HOST_MAP_BUFS];
+	void *snp_certs_data;
+	u32 snp_certs_len;
+	struct mutex snp_certs_lock;
+	struct sev_user_data_snp_config snp_config;
 };
 
 int sev_dev_init(struct psp_device *psp);
diff --git a/include/uapi/linux/psp-sev.h b/include/uapi/linux/psp-sev.h
index ffd60e8b0a31..60e7a8d1a18e 100644
--- a/include/uapi/linux/psp-sev.h
+++ b/include/uapi/linux/psp-sev.h
@@ -29,6 +29,8 @@ enum {
 	SEV_GET_ID,	/* This command is deprecated, use SEV_GET_ID2 */
 	SEV_GET_ID2,
 	SNP_PLATFORM_STATUS,
+	SNP_SET_EXT_CONFIG,
+	SNP_GET_EXT_CONFIG,
 
 	SEV_MAX,
 };
@@ -190,6 +192,21 @@ struct sev_user_data_snp_config {
 	__u8 rsvd[52];
 } __packed;
 
+/**
+ * struct sev_data_snp_ext_config - system wide configuration value for SNP.
+ *
+ * @config_address: address of the struct sev_user_data_snp_config or 0 when
+ *		reported_tcb does not need to be updated.
+ * @certs_address: address of extended guest request certificate chain or
+ *              0 when previous certificate should be removed on SNP_SET_EXT_CONFIG.
+ * @certs_len: length of the certs
+ */
+struct sev_user_data_ext_snp_config {
+	__u64 config_address;		/* In */
+	__u64 certs_address;		/* In */
+	__u32 certs_len;		/* In */
+};
+
 /**
  * struct sev_issue_cmd - SEV ioctl parameters
  *
-- 
2.25.1

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