[Xen-devel] Re: [PATCH xen-unstable] Remove PSE flag from guest

To:	Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Subject:	[Xen-devel] Re: [PATCH xen-unstable] Remove PSE flag from guest CR4
From:	Dave McCracken <dcm@xxxxxxxx>
Date:	Mon, 14 Sep 2009 12:53:38 -0500
Cc:	Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Xen Developers List <xen-devel@xxxxxxxxxxxxxxxxxxx>
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On Monday 14 September 2009, Keir Fraser wrote:
> If you hide PSE in CR4 and CPUID, how does the guest know it can use
> superpages?

Linux assumes it will just work.

Since hugepages in Linux are an optional feature the kernel will boot even on 
a machine that doesn't support PSE.  Applications that use hugepages will get 
a nasty error.

With the PSE bit set in CPUID Linux tries to do things like map the entire 
kernel in hugepages.

Dave McCracken

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[Xen-devel] Re: [PATCH xen-unstable] Remove PSE flag from guest CR4