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

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Date:	Mon, 12 Oct 2015 21:15:44 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Borislav Petkov <bp@...e.de>
Cc:	Chen Yu <yu.c.chen@...el.com>, mingo@...hat.com, pavel@....cz,
	tglx@...utronix.de, hpa@...or.com, rui.zhang@...el.com,
	luto@...nel.org, linux@...izon.com, dsmythies@...us.net,
	linux-pm@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, marcin.kaszewski@...el.com
Subject: Re: [PATCH][v5] x86, suspend: Save/restore extra MSR registers for suspend

On Monday, October 12, 2015 06:37:50 PM Borislav Petkov wrote:
> 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.
> 
> 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.
> 
> Btw, why can't that BIOS be fixed instead?

Because it's been shipped to users.

Thanks,
Rafael

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