linux-kernel - Re: [PATCH 1/2] x86/mm/pat: Change pat

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Date:	Mon, 14 Mar 2016 21:11:16 -0600
From:	Toshi Kani <toshi.kani@....com>
To:	"Luis R. Rodriguez" <mcgrof@...nel.org>,
	Borislav Petkov <bp@...en8.de>
Cc:	"mingo@...nel.org" <mingo@...nel.org>,
	"hpa@...or.com" <hpa@...or.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"jgross@...e.com" <jgross@...e.com>,
	"paul.gortmaker@...driver.com" <paul.gortmaker@...driver.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	xen-devel@...ts.xenproject.org, boris.ostrovsky@...cle.com
Subject: Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT
 table

On Tue, 2016-03-15 at 01:29 +0100, Luis R. Rodriguez wrote:
> I like this approach more as it stuff more PAT setup on its own type
> of calls, but:
> 
> On Sat, Mar 12, 2016 at 12:55:44PM +0100, Borislav Petkov wrote:
> > diff --git a/arch/x86/kernel/cpu/mtrr/main.c
> > b/arch/x86/kernel/cpu/mtrr/main.c
> > index 10f8d4796240..5c442b4bd52a 100644
> > --- a/arch/x86/kernel/cpu/mtrr/main.c
> > +++ b/arch/x86/kernel/cpu/mtrr/main.c
> > @@ -759,8 +761,11 @@ void __init mtrr_bp_init(void)
> >  		}
> >  	}
> >  
> > -	if (!mtrr_enabled())
> > +	if (!__mtrr_enabled) {
> >  		pr_info("MTRR: Disabled\n");
> > +		pat_disable("PAT disabled by MTRR");
> > +		pat_setup();
> > +	}
> >  }
> 
> This hunk would break PAT on Xen.

Can you try the attached patches?  They apply on top of my original patch-
set.  With this change, PAT code generally supports Xen, and the PAT init
code in Xen is now removed.  If they look OK, I will reorganize the patch
series.

Thanks,
-Toshi
View attachment "03-pat-emu.patch" of type "text/x-patch" (3382 bytes)

View attachment "04-xen-mtrr.patch" of type "text/x-patch" (2197 bytes)