linux-kernel - Re: [PATCH] ACPI, APEI, Add APEI

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Date:	Thu, 16 Jun 2011 02:38:12 +0100
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Huang Ying <ying.huang@...el.com>
Cc:	Len Brown <lenb@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>,
	"Luck, Tony" <tony.luck@...el.com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH] ACPI, APEI, Add APEI _OSC support

On Thu, Jun 16, 2011 at 08:40:11AM +0800, Huang Ying wrote:
> On 06/15/2011 08:17 PM, Matthew Garrett wrote:
> >> You means the "APEI Support" bit for standard UUID?  Do you know which
> >> machine uses this bit?  I can write the code, but I have no machine to
> >> test it.
> > 
> > I have access to a Dell system that uses this.
> 
> Great! Can you help us to test the code?

Yup, no problem.

> > Urgh. One machine I've looked at enables APEI if the WHEA _OSC call is 
> > made, and then clears a flag if any other _OSC call is made. In that 
> > specific case it doesn't seem to matter (the flag never actually gets 
> > checked in any of the other codepaths), but it seems that the intention 
> > is for the generic call to be made and the WHEA one to be made after 
> > that.
> 
> Yes.  The WHEA call should be made after the generic one.  Another
> situation is as follow:
> 
> - Generic _OSC call without "APEI Support" bit is called (in
> acpi_bus_osc_support).
> 
> - After some time, when we think it is good to turn on firmware first
> mode fully, usually after we checking HEST and initializing
> corresponding module, we make generic _OSC call with "APEI Support" bit
> to turn on firmware first mode fully in standard way.
> 
> Is it a good idea to make generic _OSC call twice, one without "APEI
> Support" bit, the other with "APEI Support" bit?

I think we probably need to make the HEST decision early, and use that 
to decide how to make the generic call. Our experience has been that 
many firmware vendors only expect _OSC to be called once with any given 
UUID - multiple calls can result in unexpected behaviour.

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