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Date: Tue, 2 Dec 2014 11:41:35 +0800
From: Gonglei <arei.gonglei@huawei.com>
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Subject: Re: [Qemu-devel] [BUG] Redhat-6.4_64bit-guest kernel panic with
 cpu-passthrough and guest numa
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Huangweidong (C)" <weidong.huang@huawei.com>, "benoit@irqsave.net" <benoit@irqsave.net>, "wangxin (U)" <wangxinxin.wang@huawei.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, "Huangpeng (Peter)" <peter.huangpeng@huawei.com>, "Herongguang (Stephen)" <herongguang.he@huawei.com>

On 2014/12/1 17:48, Paolo Bonzini wrote:

> 
> 
> On 28/11/2014 03:38, Gonglei wrote:
>>>> Can you find what line of kernel/sched.c it is?
>> Yes, of course. See below please:
>> "sgs->avg_load = (sgs->group_load * SCHED_LOAD_SCALE) / group->cpu_power; "
>> in update_sg_lb_stats(), file sched.c, line 4094
>> And I can share the cause of we found. After commit 787aaf57(target-i386:
>> forward CPUID cache leaves when -cpu host is used), guest will get cpu cache
>> from host when -cpu host is used. But if we configure guest numa:
>>   node 0 cpus 0~7
>>   node 1 cpus 8~15
>> then the numa nodes lie in the same host cpu cache (cpus 0~16).
>> When the guest os boot, calculate group->cpu_power, but the guest find thoes
>> two different nodes own the same cache, then node1's group->cpu_power
>> will not be valued, just is the initial value '0'. And when vcpu is scheduled,
>> division by 0 causes kernel panic.
> 
> Thanks.  Please open a Red Hat bugzilla with the information, and Cc
> Larry Woodman <lwoodman@redhat.com> who fixed a few instances of this in
> the past.
> 

Hi, Paolo

A bug has been reported:
https://bugzilla.redhat.com/process_bug.cgi

Regards,
-Gonglei