crypto: ccp: Use the stack and common buffer for INIT command

Drop the dedicated init_cmd_buf and instead use a local variable.  Now
that the low level helper uses an internal buffer for all commands,
using the stack for the upper layers is safe even when running with
CONFIG_VMAP_STACK=y.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210406224952.4177376-8-seanjc@google.com>
Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>
Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

drivers/crypto/ccp/sev-dev.c

@@ -234,6 +234,7 @@ static int sev_do_cmd(int cmd, void *data, int *psp_ret)
 static int __sev_platform_init_locked(int *error)
 {
 	struct psp_device *psp = psp_master;
+	struct sev_data_init data;
 	struct sev_device *sev;
 	int rc = 0;
 
@@ -245,6 +246,7 @@ static int __sev_platform_init_locked(int *error)
 	if (sev->state == SEV_STATE_INIT)
 		return 0;
 
+	memset(&data, 0, sizeof(data));
 	if (sev_es_tmr) {
 		u64 tmr_pa;
 
@@ -254,12 +256,12 @@ static int __sev_platform_init_locked(int *error)
 		 */
 		tmr_pa = __pa(sev_es_tmr);
 
-		sev->init_cmd_buf.flags |= SEV_INIT_FLAGS_SEV_ES;
-		sev->init_cmd_buf.tmr_address = tmr_pa;
-		sev->init_cmd_buf.tmr_len = SEV_ES_TMR_SIZE;
+		data.flags |= SEV_INIT_FLAGS_SEV_ES;
+		data.tmr_address = tmr_pa;
+		data.tmr_len = SEV_ES_TMR_SIZE;
 	}
 
-	rc = __sev_do_cmd_locked(SEV_CMD_INIT, &sev->init_cmd_buf, error);
+	rc = __sev_do_cmd_locked(SEV_CMD_INIT, &data, error);
 	if (rc)
 		return rc;
 

drivers/crypto/ccp/sev-dev.h

@@ -46,7 +46,6 @@ struct sev_device {
 	unsigned int int_rcvd;
 	wait_queue_head_t int_queue;
 	struct sev_misc_dev *misc;
-	struct sev_data_init init_cmd_buf;
 
 	u8 api_major;
 	u8 api_minor;