linux-kernel - Re: [PATCH 0/2] Quieten softlockup detector on virtualised kernels

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Date:	Fri, 9 Jan 2015 09:56:51 -0500
From:	Don Zickus <dzickus@...hat.com>
To:	Cyril Bur <cyrilbur@...il.com>
Cc:	linux-kernel@...r.kernel.org, mpe@...erman.id.au,
	drjones@...hat.com, akpm@...ux-foundation.org, mingo@...nel.org,
	uobergfe@...hat.com, chaiw.fnst@...fujitsu.com, cl@...u.com,
	fabf@...net.be, atomlin@...hat.com, benzh@...omium.org,
	mtosatti@...hat.com
Subject: Re: [PATCH 0/2] Quieten softlockup detector on virtualised kernels

On Fri, Jan 09, 2015 at 02:15:00PM +1100, Cyril Bur wrote:
> > 
> > I am not too familar with it, but the kernel/watchdog.c code has calls to
> > kvm_check_and_clear_guest_paused(), which is probably a good place to
> > start.
> > 
> Ah yes that, I did initially have a look at what it does when I
> undertook to solve the problem on power and I suppose the two solutions
> are similar in that they both just use a virtualised time source. The
> similarities stop there though, the paravirtualised clock that x86 uses
> provides (as the name of the function implies) a 'was paused' flag.
> Obviously the flag isn't something the vtb register on power8 can
> provide and since we have a vtb, its preferable to use that.
> Perhaps x86 can do something with running_clock?

Marcello?  Drew?

Cheers,
Don

> 
> Regards,
> 
> Cyril
> 
> > Cheers,
> > Don
> > 
> > > 
> > > > Not sure if that is useful or could be incoporated into the power8 code.
> > > > Though to be honest I am curious if the steal_time code could be ported to
> > > > your solution as it seems the watchdog code could remove all the
> > > > steal_time warts.
> > > Happy to help sus out the situation here, again, if you could pass on
> > > what the x86 guys are working on, thanks.
> > > 
> > > 
> > > Thanks,
> > > 
> > > Cyril
> > > > I have cc'd Marcelo into this discussion as he was the last person I
> > > > remember talking with about this problem.
> > > > 
> > > > Cheers,
> > > > Don
> > > 
> > > 
> 
> 
> 
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