linux-kernel - Re: [PATCH -v4 5/5] x86,smp: limit spinlock delay on virtual machines

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Date:	Wed, 06 Feb 2013 12:05:26 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>,
	linux-kernel@...r.kernel.org, aquini@...hat.com, walken@...gle.com,
	eric.dumazet@...il.com, lwoodman@...hat.com, knoel@...hat.com,
	chegu_vinod@...com, raghavendra.kt@...ux.vnet.ibm.com,
	mingo@...hat.com
Subject: Re: [PATCH -v4 5/5] x86,smp: limit spinlock delay on virtual machines

On 02/04/2013 09:02 AM, Borislav Petkov wrote:
> On Mon, Feb 04, 2013 at 08:50:33AM -0500, Rik van Riel wrote:
>> We need to know whether we are actually running on top of a
>> hypervisor, not whether we have the code compiled in to do so.
>
> Oh ok, I see.
>
> The thing is, if CONFIG_PARAVIRT_GUEST is disabled, x86_hyper won't
> exist, see: http://marc.info/?l=linux-kernel&m=135936817627848&w=2
>
> So maybe the hypervisor guest should itself take care of this and upon
> init it should set the max_spinlock_delay in init_hypervisor() instead?
> Seems only fair to me...

I ended up making the call from init_hypervisor_platform, which
already does the check for x86_hyper itself, allowing me to not
check x86_hyper at all from smp.c

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