From mboxrd@z Thu Jan  1 00:00:00 1970
From: "H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
Subject: Re: EFI runtime and kexec
Date: Fri, 01 Mar 2013 15:50:03 -0800
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To: Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org>
Cc: David Woodhouse <dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, Matt Fleming <matt-HNK1S37rvNbeXh+fF434Mdi2O/JbrIOy@public.gmane.org>, linux-efi <linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Matthew Garrett <mjg59-1xO5oi07KQx4cg9Nei1l7Q@public.gmane.org>
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On 03/01/2013 03:07 PM, Borislav Petkov wrote:
> 
> Hmm, yeah, that's nasty. This also means option #2 can go too because
> of the fixed addresses. Option #1 is also kinda polluting user address
> space so maybe the most elegant one would be #4, AFAICT.
> 

No, it doesn't pollute the user address space, because the EFI BIOS is
effectively a process.  We *have* to switch cr3 anyway around EFI calls,
because BIOSes in the field are known to use physical addresses instead
of virtual.

If Windows really does map EFI BIOS 1:1 then that explains why, and is
probably going to be the stable thing going forward.

	-hpa