Re: [Xen-devel] Guest soft lockups with "xen: make xen_qlock_wait() nestable"

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

On 07/11/18 23:34, Boris Ostrovsky wrote:
> On 11/7/18 4:30 AM, Sander Eikelenboom wrote:
>> Hi Juergen / Boris,
>>
>> Last week i tested Linux kernel 4.19.0 stable with the Xen "for-linus-4.20" 
>> branch pulled on top.
>> Unfortunately i was seeing guests lockup after some time, see below for the 
>> logging from one of the guest
>> which i was able to capture.
>> Reverting "xen: make xen_qlock_wait() nestable" 
>> 7250f6d35681dfc44749d90598a2d51a118ce2b8,
>> made the lockups disappear.
>>
>> These guests are stressed quite hard in both CPU and networking, 
>> so they are probably more susceptible to locking issues.
>>
>> System is a AMD phenom x6, running Xen-unstable.
>>
>> Any ideas ?
> 
> 
> By any chance, is VMPU on?
> 
> 
> -boris
> 

Had to look up what that is :), but seems only applicable to PV guests if i'm 
correct ?

I'm only running PVH and HVM guests at the moment, except for dom0 of course,
which reports:
    [    0.941407] VPMU disabled by hypervisor.

These soft lockups were in a HVM guest (if i remember correctly, i have seen
a PVH guest lockup as well after a while (also a quite heavy cpu/network 
stressed one).

--
Sander



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