linux-kernel - Re: [tip:x86/reboot] [PATCH] x86: Try the BIOS reboot method before the PCI reboot method

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Date:	Sun, 06 Apr 2014 11:40:04 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Matthew Garrett <mjg59@...f.ucam.org>
CC:	"Li, Aubrey" <aubrey.li@...ux.intel.com>,
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, rostedt@...dmis.org,
	tglx@...utronix.de, linux-tip-commits@...r.kernel.org,
	Adam Williamson <awilliam@...hat.com>
Subject: Re: [tip:x86/reboot] [PATCH] x86: Try the BIOS reboot method before
 the PCI reboot method

On 04/06/2014 10:40 AM, One Thousand Gnomes wrote:
> On Fri, 4 Apr 2014 16:13:59 +0100
> Matthew Garrett <mjg59@...f.ucam.org> wrote:
> 
>> On Fri, Apr 04, 2014 at 09:38:57PM +0800, Li, Aubrey wrote:
>>
>>> I don't think there is enough justification to revert the patch. We
>>> introduce EFI into the default list, we didn't see any reason to remove
>>> it out so far.
>>
>> We should be using the EFI method, yes. But it seems that CF9 isn't 
>> safe, so we should drop that.
>>
> 
> Windows does not use CF9 and there are known, documented cases where CF9
> will not work reliably. That includes reliable reboot on some Baytrail
> systems. (Erratum VLT60 and VLT62).
> 
> So we really shouldn't be doing 0xCF9 except as a last resort if we are
> still alive and have been through the official reboot methods.
> 

No question. The question at hand is if we should do it after all other
non-terminal (BIOS, triple) methods have been tried.

	-hpa


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