linux-kernel - Re: mtrr failure, 3.1-rc1

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Date:	Thu, 25 Aug 2011 10:43:01 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Anders Eriksson <aeriksson@...tmail.fm>,
	Peter Anvin <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Sergei Shtylyov <sshtylyov@...mvista.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: mtrr failure, 3.1-rc1

On Thu, 2011-08-25 at 09:46 -0700, Tejun Heo wrote:
> Hello,
> 
> On Thu, Aug 25, 2011 at 08:55:12AM -0700, Linus Torvalds wrote:
> > Hmm. Some of those commits are marked for stable too.
> > 
> > I'm adding appropriate parties to the discussion (authors and
> > sign-offs from the five commits that that merge brings in), but it
> > would also be great if you could bisect exactly which commit broke for
> > you. You can make it quick by just doing
> > 
> >   git bisect start
> >   git bisect bad dc43d9fa73d82083656fb9c02f4823bcdcfb9f91
> >   git bisect good dc43d9fa73d82083656fb9c02f4823bcdcfb9f91^
> > 
> > and it should take just a couple of tests. I *assume* it's the
> > stop_machine changes by Tejun &co, but who knows..
> > 
> > Anders, is this a single-CPU system?
> 
> Indeed, while removing custom rendezvous code and switching to
> stop_machine, commit 192d8857427d "x86, mtrr: use stop_machine APIs
> for doing MTRR rendezvous" completely dropped mtrr setting code on
> !CONFIG_SMP.

oops. My bad. Linus, Bad commit is not marked for stable.

I was able to reproduce the issue and tested the below patch. It looks
good.

Thanks.

Acked-by: Suresh Siddha <suresh.b.siddha@...el.com>

> 
> Anders, if your kernel didn't have SMP turned on, can you please
> verify the following patch fixes the problem?
> 
> Thanks.
> 
> diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
> index 08119a3..6b96110 100644
> --- a/arch/x86/kernel/cpu/mtrr/main.c
> +++ b/arch/x86/kernel/cpu/mtrr/main.c
> @@ -149,7 +149,6 @@ struct set_mtrr_data {
>   */
>  static int mtrr_rendezvous_handler(void *info)
>  {
> -#ifdef CONFIG_SMP
>  	struct set_mtrr_data *data = info;
>  
>  	/*
> @@ -171,7 +170,6 @@ static int mtrr_rendezvous_handler(void *info)
>  	} else if (mtrr_aps_delayed_init || !cpu_online(smp_processor_id())) {
>  		mtrr_if->set_all();
>  	}
> -#endif
>  	return 0;
>  }
>  


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