[PATCH 5/6] KVM: SEV: use mutex guard in snp_handle_guest_req()

[Carlos López]

Simplify the error paths in snp_handle_guest_req() by using a mutex
guard, allowing early return instead of using gotos.

Signed-off-by: Carlos López <clopez@xxxxxxx>
---
 arch/x86/kvm/svm/sev.c | 23 ++++++++---------------
 1 file changed, 8 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 47ff5267ab01..5f46b7f073b0 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -4090,12 +4090,10 @@ static int snp_handle_guest_req(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t resp_
 	if (!sev_snp_guest(kvm))
 		return -EINVAL;
 
-	mutex_lock(&sev->guest_req_mutex);
+	guard(mutex)(&sev->guest_req_mutex);
 
-	if (kvm_read_guest(kvm, req_gpa, sev->guest_req_buf, PAGE_SIZE)) {
-		ret = -EIO;
-		goto out_unlock;
-	}
+	if (kvm_read_guest(kvm, req_gpa, sev->guest_req_buf, PAGE_SIZE))
+		return -EIO;
 
 	data.gctx_paddr = __psp_pa(sev->snp_context);
 	data.req_paddr = __psp_pa(sev->guest_req_buf);
@@ -4108,21 +4106,16 @@ static int snp_handle_guest_req(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t resp_
 	 */
 	ret = sev_issue_cmd(kvm, SEV_CMD_SNP_GUEST_REQUEST, &data, &fw_err);
 	if (ret && !fw_err)
-		goto out_unlock;
+		return ret;
 
-	if (kvm_write_guest(kvm, resp_gpa, sev->guest_resp_buf, PAGE_SIZE)) {
-		ret = -EIO;
-		goto out_unlock;
-	}
+	if (kvm_write_guest(kvm, resp_gpa, sev->guest_resp_buf, PAGE_SIZE))
+		return -EIO;
 
 	/* No action is requested *from KVM* if there was a firmware error. */
 	svm_vmgexit_no_action(svm, SNP_GUEST_ERR(0, fw_err));
 
-	ret = 1; /* resume guest */
-
-out_unlock:
-	mutex_unlock(&sev->guest_req_mutex);
-	return ret;
+	/* resume guest */
+	return 1;
 }
 
 static int snp_handle_ext_guest_req(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t resp_gpa)
-- 
2.51.0