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Re: [libvirt] [PATCH] cpu: break out when a right cpuCandidate found



On Thu, Feb 13, 2014 at 07:44:20AM +0000, Wangyufei (James) wrote:
> >From 8123c5d64f940fa0fb0de32fc5e68035980b6b01 Mon Sep 17 00:00:00 2001
> From: WangYufei <james wangyufei huawei com>
> Date: Thu, 13 Feb 2014 07:17:11 +0000
> Subject: [PATCH] cpu: break out when a right cpuCandidate found
>
> In function x86Decode there's a code segment in while cycle like this:
>         if (cpuModel == NULL
>             || cpuModel->nfeatures > cpuCandidate->nfeatures) {
>             virCPUDefFree(cpuModel);
>             cpuModel = cpuCandidate;
>             cpuData = candidate->data;
>         } else {
>             virCPUDefFree(cpuCandidate);
>         }
> when it finds the right cpuCandidate, it doesn't break out the cycle, but continues
> run in it, and cpuModel will never get a new value, it's meaningless. It should
> break out when a right cpuCndidate found.
>

Inside this condition, the code doesn't always choose the perfect
candidate.  You don't consider a situation when the cycle continues
and the next candidate model is the preferred one, thus satisfies
previous condition, which looks like this:

if (preferred && STREQ(cpuCandidate->model, preferred)) {
    virCPUDefFree(cpuModel);
    cpuModel = cpuCandidate;
    cpuData = candidate->data;
    break;
}

Where the "perfect" cpuModel is found, used and the condition breaks
(appropriately this time).  But I could also misunderstood the code.

Martin

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