linux-kernel - [PATCH] KVM: s390: Pass initialized arg even if unused

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Date:   Wed, 24 Aug 2022 17:30:11 +0200
From:   Janis Schoetterl-Glausch <scgl@...ux.ibm.com>
To:     Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>
Cc:     Janis Schoetterl-Glausch <scgl@...ux.ibm.com>,
        kernel test robot <lkp@...el.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        David Hildenbrand <david@...hat.com>,
        Sven Schnelle <svens@...ux.ibm.com>, kvm@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] KVM: s390: Pass initialized arg even if unused

This silences smatch warnings reported by kbuild bot:
arch/s390/kvm/gaccess.c:859 guest_range_to_gpas() error: uninitialized symbol 'prot'.
arch/s390/kvm/gaccess.c:1064 access_guest_with_key() error: uninitialized symbol 'prot'.

This is because it cannot tell that the value is not used in this case.
The trans_exc* only examine prot if code is PGM_PROTECTION.
Pass a dummy value for other codes.

Reported-by: kernel test robot <lkp@...el.com>
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Janis Schoetterl-Glausch <scgl@...ux.ibm.com>
---
 arch/s390/kvm/gaccess.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index 082ec5f2c3a5..89186701116a 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -489,6 +489,8 @@ enum prot_type {
 	PROT_TYPE_ALC  = 2,
 	PROT_TYPE_DAT  = 3,
 	PROT_TYPE_IEP  = 4,
+	/* Dummy value for passing an initialized value when code != PGM_PROTECTION */
+	PROT_NONE,
 };
 
 static int trans_exc_ending(struct kvm_vcpu *vcpu, int code, unsigned long gva, u8 ar,
@@ -503,6 +505,7 @@ static int trans_exc_ending(struct kvm_vcpu *vcpu, int code, unsigned long gva,
 
 	switch (code) {
 	case PGM_PROTECTION:
+		WARN(unlikely(prot == PROT_NONE), "Invalid prot argument");
 		switch (prot) {
 		case PROT_TYPE_IEP:
 			tec->b61 = 1;
@@ -519,6 +522,8 @@ static int trans_exc_ending(struct kvm_vcpu *vcpu, int code, unsigned long gva,
 		case PROT_TYPE_DAT:
 			tec->b61 = 1;
 			break;
+		case PROT_NONE:
+			/* We should never get here, acts like termination */
 		}
 		if (terminate) {
 			tec->b56 = 0;
@@ -968,8 +973,10 @@ static int guest_range_to_gpas(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
 				return rc;
 		} else {
 			gpa = kvm_s390_real_to_abs(vcpu, ga);
-			if (kvm_is_error_gpa(vcpu->kvm, gpa))
+			if (kvm_is_error_gpa(vcpu->kvm, gpa)) {
 				rc = PGM_ADDRESSING;
+				prot = PROT_NONE;
+			}
 		}
 		if (rc)
 			return trans_exc(vcpu, rc, ga, ar, mode, prot);
@@ -1112,8 +1119,6 @@ int access_guest_with_key(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
 		if (rc == PGM_PROTECTION && try_storage_prot_override)
 			rc = access_guest_page_with_key(vcpu->kvm, mode, gpas[idx],
 							data, fragment_len, PAGE_SPO_ACC);
-		if (rc == PGM_PROTECTION)
-			prot = PROT_TYPE_KEYC;
 		if (rc)
 			break;
 		len -= fragment_len;
@@ -1123,6 +1128,10 @@ int access_guest_with_key(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
 	if (rc > 0) {
 		bool terminate = (mode == GACC_STORE) && (idx > 0);
 
+		if (rc == PGM_PROTECTION)
+			prot = PROT_TYPE_KEYC;
+		else
+			prot = PROT_NONE;
 		rc = trans_exc_ending(vcpu, rc, ga, ar, mode, prot, terminate);
 	}
 out_unlock:
-- 
2.34.1