x86/sev-es: Convert to insn_decode()

Simplify code, no functional changes.
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210304174237.31945-14-bp@alien8.de

arch/x86/kernel/sev-es.c

@@ -254,7 +254,6 @@ static int vc_fetch_insn_kernel(struct es_em_ctxt *ctxt,
 static enum es_result __vc_decode_user_insn(struct es_em_ctxt *ctxt)
 {
 	char buffer[MAX_INSN_SIZE];
-	enum es_result ret;
 	int res;
 
 	res = insn_fetch_from_user_inatomic(ctxt->regs, buffer);
@@ -268,16 +267,16 @@ static enum es_result __vc_decode_user_insn(struct es_em_ctxt *ctxt)
 	if (!insn_decode_from_regs(&ctxt->insn, ctxt->regs, buffer, res))
 		return ES_DECODE_FAILED;
 
-	ret = ctxt->insn.immediate.got ? ES_OK : ES_DECODE_FAILED;
-
-	return ret;
+	if (ctxt->insn.immediate.got)
+		return ES_OK;
+	else
+		return ES_DECODE_FAILED;
 }
 
 static enum es_result __vc_decode_kern_insn(struct es_em_ctxt *ctxt)
 {
 	char buffer[MAX_INSN_SIZE];
-	enum es_result ret;
-	int res;
+	int res, ret;
 
 	res = vc_fetch_insn_kernel(ctxt, buffer);
 	if (res) {
@@ -287,12 +286,11 @@ static enum es_result __vc_decode_kern_insn(struct es_em_ctxt *ctxt)
 		return ES_EXCEPTION;
 	}
 
-	insn_init(&ctxt->insn, buffer, MAX_INSN_SIZE, 1);
-	insn_get_length(&ctxt->insn);
-
-	ret = ctxt->insn.immediate.got ? ES_OK : ES_DECODE_FAILED;
-
-	return ret;
+	ret = insn_decode(&ctxt->insn, buffer, MAX_INSN_SIZE, INSN_MODE_64);
+	if (ret < 0)
+		return ES_DECODE_FAILED;
+	else
+		return ES_OK;
 }
 
 static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt)