> -----Original Message----- > From: Martin Kletzander [mailto:mkletzan@xxxxxxxxxx] > Sent: Thursday, February 13, 2014 6:08 PM > To: Wangyufei (James) > Cc: libvir-list@xxxxxxxxxx; Wangrui (K); Zhaoyanbin (A) > Subject: Re: [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@xxxxxxxxxx> > > 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. > Well, thank you for your reply. I have seen preferred, but there's no where to modify the value of preferred in the cycle. So the preferred is a fixed value. In this case, I can make it better to mdify the patch like this: --- a/src/cpu/cpu_x86.c +++ b/src/cpu/cpu_x86.c @@ -1558,6 +1558,7 @@ x86Decode(virCPUDefPtr cpu, virCPUDefFree(cpuModel); cpuModel = cpuCandidate; cpuData = candidate->data; + if (!preferred) + break; } else { virCPUDefFree(cpuCandidate); } In my situation： virQEMUCapsInitCPU ->cpuDecode ->x86Decode if (!(data = cpuNodeData(arch)) || cpuDecode(cpu, data, NULL, 0, NULL) < 0) goto cleanup; preferred is always NULL. So we can do it better. > Martin -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list