crypto: ccp: Provide an API to issue SEV and SNP commands

Export sev_do_cmd() as a generic API for the hypervisor to issue
commands to manage an SEV or an SNP guest. The commands for SEV and SNP
are defined in the SEV and SEV-SNP firmware specifications.
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@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/20240126041126.1927228-15-michael.roth@amd.com

drivers/crypto/ccp/sev-dev.c

@@ -431,7 +431,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
 	return ret;
 }
 
-static int sev_do_cmd(int cmd, void *data, int *psp_ret)
+int sev_do_cmd(int cmd, void *data, int *psp_ret)
 {
 	int rc;
 
@@ -441,6 +441,7 @@ static int sev_do_cmd(int cmd, void *data, int *psp_ret)
 
 	return rc;
 }
+EXPORT_SYMBOL_GPL(sev_do_cmd);
 
 static int __sev_init_locked(int *error)
 {

include/linux/psp-sev.h

@@ -915,6 +915,22 @@ int sev_guest_df_flush(int *error);
  */
 int sev_guest_decommission(struct sev_data_decommission *data, int *error);
 
+/**
+ * sev_do_cmd - issue an SEV or an SEV-SNP command
+ *
+ * @cmd: SEV or SEV-SNP firmware command to issue
+ * @data: arguments for firmware command
+ * @psp_ret: SEV command return code
+ *
+ * Returns:
+ * 0 if the SEV device successfully processed the command
+ * -%ENODEV    if the PSP device is not available
+ * -%ENOTSUPP  if PSP device does not support SEV
+ * -%ETIMEDOUT if the SEV command timed out
+ * -%EIO       if PSP device returned a non-zero return code
+ */
+int sev_do_cmd(int cmd, void *data, int *psp_ret);
+
 void *psp_copy_user_blob(u64 uaddr, u32 len);
 
 #else	/* !CONFIG_CRYPTO_DEV_SP_PSP */
@@ -930,6 +946,9 @@ sev_guest_deactivate(struct sev_data_deactivate *data, int *error) { return -ENO
 static inline int
 sev_guest_decommission(struct sev_data_decommission *data, int *error) { return -ENODEV; }
 
+static inline int
+sev_do_cmd(int cmd, void *data, int *psp_ret) { return -ENODEV; }
+
 static inline int
 sev_guest_activate(struct sev_data_activate *data, int *error) { return -ENODEV; }