linux-kernel - Re: [PATCH] EFI: Only set regions uncacheable if they support it

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Message-ID: <20120315145403.GA5321@srcf.ucam.org>
Date:	Thu, 15 Mar 2012 14:54:03 +0000
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	linux-kernel@...r.kernel.org, x86@...nel.org,
	matt.fleming@...el.com
Subject: Re: [PATCH] EFI: Only set regions uncacheable if they support it

On Thu, Mar 15, 2012 at 07:47:57AM -0700, H. Peter Anvin wrote:

> WTF?!  That should be UC at all times... it isn't even WC-capable.
> Furthermore, we may need this region (assuming there is actually a video
> card there.)

I don't think we'll ever use this region on UEFI. What I have from Intel 
is:

"It looks like this is happening when the kernel iterates over the 
various regions in the EFI memory map. It hits a region starting at 
0xA0000 and attempts to do a CLFLUSH instruction on that address. This 
is explicitly forbidden by the SAD in (codename), thus the Machine 
Check."

> What do the fixed MTRRs look like?

Unsure. I'll try to find out.

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