linux-kernel - RE: [PATCH][v5] x86, suspend: Save/restore extra MSR registers for suspend

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Date:	Wed, 14 Oct 2015 17:41:10 +0000
From:	"Chen, Yu C" <yu.c.chen@...el.com>
To:	Borislav Petkov <bp@...e.de>
CC:	"mingo@...hat.com" <mingo@...hat.com>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	"pavel@....cz" <pavel@....cz>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"hpa@...or.com" <hpa@...or.com>,
	"Zhang, Rui" <rui.zhang@...el.com>,
	"luto@...nel.org" <luto@...nel.org>,
	"linux@...izon.com" <linux@...izon.com>,
	"dsmythies@...us.net" <dsmythies@...us.net>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Kaszewski, Marcin" <marcin.kaszewski@...el.com>
Subject: RE: [PATCH][v5] x86, suspend: Save/restore extra MSR registers for
 suspend

Hi, Boris, thanks for you reply

> -----Original Message-----
> From: Borislav Petkov [mailto:bp@...e.de]
> Sent: Tuesday, October 13, 2015 12:38 AM
> To: Chen, Yu C
> Cc: mingo@...hat.com; rjw@...ysocki.net; pavel@....cz;
> tglx@...utronix.de; hpa@...or.com; Zhang, Rui; luto@...nel.org;
> linux@...izon.com; dsmythies@...us.net; linux-pm@...r.kernel.org;
> x86@...nel.org; linux-kernel@...r.kernel.org; Kaszewski, Marcin
> Subject: Re: [PATCH][v5] x86, suspend: Save/restore extra MSR registers for
> suspend
> 
> On Sun, Oct 11, 2015 at 11:20:01AM +0800, Chen Yu wrote:
> > A bug is reported(https://bugzilla.redhat.com/show_bug.cgi?id=1227208)
> 
> I get:
> 
> "You are not authorized to access bug #1227208.
> 
> Most likely the bug has been restricted for internal development processes
> and we cannot grant access."
> 
> > that, after resumed from S3, CPU is running at a low speed.
> > After investigation, it is found that, BIOS has modified the value of
> > THERM_CONTROL register during S3, and changes it from 0 to 0x10 (thus
> > changes the clock modulation from reserved to enabled), since value of
> > 0x10 means CPU can only get 25% of the Duty Cycle, this triggers the
> > problem.
> 
> Is this what the bug described above is? In any case, please remove the
> private bugzilla link and describe the bug in text here.
OK, will remove the link here and inside the code.
> 
> Also, from reading the other thread about the v4 patch, it sounds like
> intel_pstate can't handle the clock modulation properly, according to what
> Doug says.
> 
> So let's have this aspect sorted out properly first please before adding yet
> another ugly BIOS workaround.
> 
Well, that might be another driver bug IMO. I'll dig into that one.

> Btw, why can't that BIOS be fixed instead?
This bug is found on a released redhat server, so I think it would be
hard to update all users' machines. 
> 
> --
> Regards/Gruss,
>     Boris.

Best Regards,
Yu