linux-kernel - Re: [patch] x86: Introduce BOOT_EFI and BOOT

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Date:	Sun, 2 Mar 2014 23:11:54 +0000
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	"Li, Aubrey" <aubrey.li@...ux.intel.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	"alan@...ux.intel.com" <alan@...ux.intel.com>,
	linux-kernel@...r.kernel.org, Len.Brown@...el.com,
	Adam Williamson <awilliam@...hat.com>
Subject: Re: [patch] x86: Introduce BOOT_EFI and BOOT_CF9 into the reboot
 sequence loop

On Mon, Mar 03, 2014 at 06:45:15AM +0800, Li, Aubrey wrote:

> One example in my hand is, 32bit windows calls 32bit EFI firware, so
> reboot works. However, I installed 64bit linux on this 32bit EFI
> machine, so none of ACPI/KBD/EFI works.

Yes. The correct fix for that is to ensure that the 64-bit kernel can 
make 32-bit runtime services calls.

> Other cases even if we figured out why ACPI/KBD/EFI don't work, we still
> have to make our change in the linux kernel, because we can't change
> firmware.

That's correct, yes. If Windows is able to reboot the system and Linux 
is not, then that's a bug in the Linux kernel.

> So, if you are still suggesting we add EFI only, please let me know your
> plan about adding dmidecode table and if it's acceptable to add new
> tables, I have three waiting: ASUS-T100, Dell Venue 8 Pro, and Dell
> Venue 11 Pro.

I don't think it's acceptable to add DMI entries to the reboot table. I 
think you should add the EFI call (since we expect that to work now), 
and I have no objection to adding cf9 to the end of the list if we have 
standard PCI io ports (Windows doesn't do it, but we can hardly make 
things worse).

-- 
Matthew Garrett | mjg59@...f.ucam.org
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