crypto: ccp: Add the SNP_COMMIT command

The SNP_COMMIT command is used to commit the currently installed version
of the SEV firmware. Once committed, the firmware cannot be replaced
with a previous firmware version (cannot be rolled back). This command
will also update the reported TCB to match that of the currently
installed firmware.

  [ mdr: Note the reported TCB update in the documentation/commit. ]

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240126041126.1927228-25-michael.roth@amd.com

Author: tlendacky

Documentation/virt/coco/sev-guest.rst

@@ -151,6 +151,17 @@ 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_COMMIT
+--------------
+:Technology: sev-snp
+:Type: hypervisor ioctl cmd
+:Returns (out): 0 on success, -negative on error
+
+SNP_COMMIT is used to commit the currently installed firmware using the
+SEV-SNP firmware SNP_COMMIT command. This prevents roll-back to a previously
+committed firmware version. This will also update the reported TCB to match
+that of the currently installed firmware.
+
 3. SEV-SNP CPUID Enforcement
 ============================
 

drivers/crypto/ccp/sev-dev.c

@@ -222,6 +222,7 @@ static int sev_cmd_buffer_len(int cmd)
 	case SEV_CMD_SNP_PLATFORM_STATUS:	return sizeof(struct sev_data_snp_addr);
 	case SEV_CMD_SNP_GUEST_REQUEST:		return sizeof(struct sev_data_snp_guest_request);
 	case SEV_CMD_SNP_CONFIG:		return sizeof(struct sev_user_data_snp_config);
+	case SEV_CMD_SNP_COMMIT:		return sizeof(struct sev_data_snp_commit);
 	default:				return 0;
 	}
 
@@ -1990,6 +1991,19 @@ static int sev_ioctl_do_snp_platform_status(struct sev_issue_cmd *argp)
 	return ret;
 }
 
+static int sev_ioctl_do_snp_commit(struct sev_issue_cmd *argp)
+{
+	struct sev_device *sev = psp_master->sev_data;
+	struct sev_data_snp_commit buf;
+
+	if (!sev->snp_initialized)
+		return -EINVAL;
+
+	buf.len = sizeof(buf);
+
+	return __sev_do_cmd_locked(SEV_CMD_SNP_COMMIT, &buf, &argp->error);
+}
+
 static long sev_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
 {
 	void __user *argp = (void __user *)arg;
@@ -2044,6 +2058,9 @@ static long sev_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
 	case SNP_PLATFORM_STATUS:
 		ret = sev_ioctl_do_snp_platform_status(&input);
 		break;
+	case SNP_COMMIT:
+		ret = sev_ioctl_do_snp_commit(&input);
+		break;
 	default:
 		ret = -EINVAL;
 		goto out;

include/linux/psp-sev.h

@@ -801,6 +801,15 @@ struct sev_platform_init_args {
 	bool probe;
 };
 
+/**
+ * struct sev_data_snp_commit - SNP_COMMIT structure
+ *
+ * @len: length of the command buffer read by the PSP
+ */
+struct sev_data_snp_commit {
+	u32 len;
+} __packed;
+
 #ifdef CONFIG_CRYPTO_DEV_SP_PSP
 
 /**

include/uapi/linux/psp-sev.h

@@ -29,6 +29,7 @@ enum {
 	SEV_GET_ID,	/* This command is deprecated, use SEV_GET_ID2 */
 	SEV_GET_ID2,
 	SNP_PLATFORM_STATUS,
+	SNP_COMMIT,
 
 	SEV_MAX,
 };