linux-kernel - Re: [git pull] x86 PAT changes

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Message-ID: <20080426154123.GA7295@elte.hu>
Date:	Sat, 26 Apr 2008 17:41:23 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Gabriel C <nix.or.die@...glemail.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	Arjan van de Ven <arjan@...radead.org>,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	Avi Kivity <avi@...ranet.com>
Subject: Re: [git pull] x86 PAT changes


* Gabriel C <nix.or.die@...glemail.com> wrote:

> Ingo Molnar wrote:
> > * Gabriel C <nix.or.die@...glemail.com> wrote:
> > 
> >> Hi Ingo,
> >>
> >> When using an 64bit ( didn't got time to test 32bit now ) kernel[1] 
> >> with PAT enabled , kvm-intel does not work anymore.
> >>
> >> When modprobing kvm-intel , kvm is saying VT extension is disable by 
> >> BIOS which isn't true. When disabling PAT again ( no changes to BIOS ) 
> >> kvm-intel works again here.
> >>
> >> Is that an known problem ?
> > 
> > no, that side-effect was not known. Cc:-ed more folks.
> 
> It seems like the update triggers some compiler bug.
> 
> Setting CC_OPTIMIZE_FOR_SIZE=n fixed that btw.
> 
> I don't have the time right now but later on today I will compile 
> gcc43_svn_branch and test again with CC_OPTIMIZE_FOR_SIZE=y and see 
> what I get.
> 
> Ingo sorry for the noise.

no problem and it's not noise even if it turns out to be a compiler 
problem - we very much want to know about them when they affect the 
kernel.

	Ingo
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