x86/sev: Carve out HV call's return value verification

Carve out the verification of the HV call return value into a separate
helper and make it more readable.

No functional changes.
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/YVbYWz%2B8J7iMTJjc@zn.tnic

arch/x86/kernel/sev-shared.c

@@ -94,25 +94,15 @@ static void vc_finish_insn(struct es_em_ctxt *ctxt)
 	ctxt->regs->ip += ctxt->insn.length;
 }
 
-static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
-					  struct es_em_ctxt *ctxt,
-					  u64 exit_code, u64 exit_info_1,
-					  u64 exit_info_2)
+static enum es_result verify_exception_info(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
 {
-	enum es_result ret;
+	u32 ret;
 
-	/* Fill in protocol and format specifiers */
-	ghcb->protocol_version = GHCB_PROTOCOL_MAX;
-	ghcb->ghcb_usage       = GHCB_DEFAULT_USAGE;
+	ret = ghcb->save.sw_exit_info_1 & GENMASK_ULL(31, 0);
+	if (!ret)
+		return ES_OK;
 
-	ghcb_set_sw_exit_code(ghcb, exit_code);
-	ghcb_set_sw_exit_info_1(ghcb, exit_info_1);
-	ghcb_set_sw_exit_info_2(ghcb, exit_info_2);
-
-	sev_es_wr_ghcb_msr(__pa(ghcb));
-	VMGEXIT();
-
-	if ((ghcb->save.sw_exit_info_1 & 0xffffffff) == 1) {
+	if (ret == 1) {
 		u64 info = ghcb->save.sw_exit_info_2;
 		unsigned long v;
 
@@ -124,19 +114,34 @@ static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
 		    ((v == X86_TRAP_GP) || (v == X86_TRAP_UD)) &&
 		    ((info & SVM_EVTINJ_TYPE_MASK) == SVM_EVTINJ_TYPE_EXEPT)) {
 			ctxt->fi.vector = v;
+
 			if (info & SVM_EVTINJ_VALID_ERR)
 				ctxt->fi.error_code = info >> 32;
-			ret = ES_EXCEPTION;
-		} else {
-			ret = ES_VMM_ERROR;
+
+			return ES_EXCEPTION;
 		}
-	} else if (ghcb->save.sw_exit_info_1 & 0xffffffff) {
-		ret = ES_VMM_ERROR;
-	} else {
-		ret = ES_OK;
 	}
 
-	return ret;
+	return ES_VMM_ERROR;
+}
+
+static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
+					  struct es_em_ctxt *ctxt,
+					  u64 exit_code, u64 exit_info_1,
+					  u64 exit_info_2)
+{
+	/* Fill in protocol and format specifiers */
+	ghcb->protocol_version = GHCB_PROTOCOL_MAX;
+	ghcb->ghcb_usage       = GHCB_DEFAULT_USAGE;
+
+	ghcb_set_sw_exit_code(ghcb, exit_code);
+	ghcb_set_sw_exit_info_1(ghcb, exit_info_1);
+	ghcb_set_sw_exit_info_2(ghcb, exit_info_2);
+
+	sev_es_wr_ghcb_msr(__pa(ghcb));
+	VMGEXIT();
+
+	return verify_exception_info(ghcb, ctxt);
 }
 
 /*