Subrata Modak wrote:
Hi Avi/Yaniv,
With gcc --version 4.4.1 20090429 (prerelease)
I get the following warning:
arch/x86/kvm/vmx.c: In function ‘vmx_intr_assist’:
arch/x86/kvm/vmx.c:3233: warning: ‘max_irr’ may be used uninitialized in this function
arch/x86/kvm/vmx.c:3233: note: ‘max_irr’ 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)) {
This function no longer exists; can you check if the current code is
susceptible?
(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.
With !kvm_lapic_enabled(), TPR_THRESHOLD is meaningless.
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
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