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

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Date:	Thu, 25 Aug 2011 18:46:49 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Anders Eriksson <aeriksson@...tmail.fm>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Peter Anvin <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Sergei Shtylyov <sshtylyov@...mvista.com>,
	linux-kernel@...r.kernel.org
Subject: Re: mtrr failure, 3.1-rc1

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.

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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