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

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Message-ID: <20130204140203.GB15452@pd.tnic>
Date:	Mon, 4 Feb 2013 15:02:03 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Rik van Riel <riel@...hat.com>
Cc:	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 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...

> After all, the majority of distribution kernels will have
> CONFIG_PARAVIRT_GUEST set, but the majority of those kernels
> will be running bare metal...

Yeah :-)

Thanks.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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