Re: [Qemu-devel] [BUG] Redhat-6.4_64bit-guest kernel panic with cpu-passthrough and guest numa

[Paolo Bonzini <pbonzini@redhat.com>]

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.

Paolo