Hi Avi/Yaniv,
With gcc --version 4.4.1 20090429 (prerelease)
I get the following warning:
arch/x86/kvm/vmx.c: In function â??vmx_intr_assistâ??:
arch/x86/kvm/vmx.c:3233: warning: â??max_irrâ?? may be used uninitialized in this function
arch/x86/kvm/vmx.c:3233: note: â??max_irrâ?? was declared here
Investigation found that:
3231 static void update_tpr_threshold(struct kvm_vcpu *vcpu)
3232 {
3233 int max_irr, tpr;
3234
3235 if (!vm_need_tpr_shadow(vcpu->kvm))
3236 return;
3237
3238 if (!kvm_lapic_enabled(vcpu) ||
3239 ((max_irr = kvm_lapic_find_highest_irr(vcpu)) == -1)) {
(max_irr = kvm_lapic_find_highest_irr(vcpu)) == -1
may not get a chance to evaluate if:
!kvm_lapic_enabled(vcpu)
evaluates to true (as the expressions are Or-ed).
3240 vmcs_write32(TPR_THRESHOLD, 0);
3241 return;
3242 }
3243
3244 tpr = (kvm_lapic_get_cr8(vcpu) & 0x0f) << 4;
3245 vmcs_write32(TPR_THRESHOLD, (max_irr > tpr) ? tpr >> 4 : max_irr >> 4);
Using (max_irr > tpr) and max_irr >> 4, without max_irr getting initialized can
cause trouble.
3246 }
I would like to propose a small fix for this by interchanging the
operands in ||, so that max_irr is initialized in all instances,
and, the warning fades away, without compromising the criteria of
conditional evaluation inside if().
Signed-Off-By: Subrata Modak <subrata@xxxxxxxxxxxxxxxxxx>,
To: Avi Kivity <avi@xxxxxxxxxxxx>
To: Yaniv Kamay <yaniv@xxxxxxxxxxxx>
To: <kvm@xxxxxxxxxxxxxxx>
Cc: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
Cc: Sachin P Sant <sachinp@xxxxxxxxxxxxxxxxxx>
Subject: [PATCH][Resend] Fix Warnining in arch/x86/kvm/vmx.c
---
--- a/arch/x86/kvm/vmx.c 2009-05-12 15:28:42.000000000 +0530
+++ b/arch/x86/kvm/vmx.c 2009-05-12 15:51:02.000000000 +0530
@@ -3235,8 +3235,8 @@ static void update_tpr_threshold(struct
if (!vm_need_tpr_shadow(vcpu->kvm))
return;
- if (!kvm_lapic_enabled(vcpu) ||
- ((max_irr = kvm_lapic_find_highest_irr(vcpu)) == -1)) {
+ if (((max_irr = kvm_lapic_find_highest_irr(vcpu)) == -1) ||
+ !kvm_lapic_enabled(vcpu)) {
vmcs_write32(TPR_THRESHOLD, 0);
return;
}
---
Regards--
Subrata
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