Re: [PATCH v2] KVM: s390: Pass initialized arg even if unused

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Am 25.08.22 um 21:25 schrieb Janis Schoetterl-Glausch:
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@xxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Janis Schoetterl-Glausch <scgl@xxxxxxxxxxxxx>

Thanks applied.
---
v1 -> v2
  * drop unlikely, WARN_ON_ONCE instead of WARN (thanks Heiko)

  arch/s390/kvm/gaccess.c | 16 +++++++++++++---
  1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index 082ec5f2c3a5..0243b6e38d36 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,
@@ -504,6 +506,10 @@ static int trans_exc_ending(struct kvm_vcpu *vcpu, int code, unsigned long gva,
  	switch (code) {
  	case PGM_PROTECTION:
  		switch (prot) {
+		case PROT_NONE:
+			/* We should never get here, acts like termination */
+			WARN_ON_ONCE(1);
+			break;
  		case PROT_TYPE_IEP:
  			tec->b61 = 1;
  			fallthrough;
@@ -968,8 +974,10 @@ 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 +1120,6 @@ 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 +1129,10 @@ 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:



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