Re: XP machine freeze

[Brad Campbell <lists2009@fnarfbargle.com>]

On 19/04/15 23:48, Nadav Amit wrote:
> Brad Campbell <lists2009@fnarfbargle.com> wrote:
>
>> On 13/04/15 22:02, Paolo Bonzini wrote:
>>> On 13/04/2015 14:45, Brad Campbell wrote:
>>>> G'day Paolo,
>>>>
>>>> Yes, on AMD and I've tried hard to reproduce it on Intel and been unable
>>>> to thus far.
>>>>
>>>> Now you mention it may be AMD specific, I have a spare motherboard and
>>>> processor sitting in a drawer. I'll bolt it together tomorrow and see if
>>>> I can reproduce it on another AMD machine. Two machines should let me
>>>> test it twice as fast.
>>>>
>>>> I got a fail this afternoon, so I'm due to reboot tonight. I'll just
>>>> revert that one suspect commit from a known bad kernel and see if that
>>>> cleans it up. If not then I'll work through the remainder of the
>>>> information in your mail. I really appreciate the attention you've paid
>>>> to this, it has been a frustrating bug for me because I'm in a position
>>>> of not knowing what I don't know, and obviously doing something wrong in
>>>> very long bisection processes.
>>> Actually, if you have time to change your course of action, please
>>> revert the one that Nadav pointed out (f210f7572bed, KVM: x86:
>>> Fix lost interrupt on irr_pending race) or cherry-pick it on top of 3.17.
>>>
>>> Paolo
>> Ok, I think we have a winner. Patch manually plopped on top of vanilla 3.17. It has never gone for anywhere near this long on a bad kernel.
>>
>> brad@srv:~$ uptime
>> 23:24:48 up 6 days,  1:01,  3 users,  load average: 1.48, 1.95, 2.48
>>
>> So this patch went into the kernel during the 3.19 release cycle? Affected kernels 3.16-3.18?
> Actually, the original bug seemed to be introduced by commit
> 33e4c68656a2e461b296ce714ec322978de85412 "KVM: Optimize searching for
> highest IRR”. So the bug goes all the way back to 2.6.32. The race that this
> patch fixes just became more apparent (i.e., likely to happen) on 3.16. It
> is fixed in 3.19.

And I can confidently state that over the years I've seen this happen a 
number of times, but in each case I was using qemu with an SDL console 
as a user-interactive VM, and a moving the mouse would restore network 
connectivity. It was obviously seriously exacerbated by something that 
went into 3.16.

I really appreciate the assistance in pinning this down. At the next 
excuse for a reboot I'll upgrade the server to a 3.19.x kernel and call 
it done.

Regards,
Brad

-- 
Dolphins are so intelligent that within a few weeks they can
train Americans to stand at the edge of the pool and throw them
fish.