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Re: [Xen-devel] Re: [PATCH 2/2] Linux support for hugepages as a Xen PV

To: Dave McCracken <dcm@xxxxxxxx>
Subject: Re: [Xen-devel] Re: [PATCH 2/2] Linux support for hugepages as a Xen PV guest
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Wed, 15 Oct 2008 14:48:22 -0700
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
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Dave McCracken wrote:
For starters, Xen currently does remove PSE from the CPUID it returns to the guest. I'll add some code to allow PSE when hugepages are enabled.

Yep.

Second, in Linux for the x86_64 architecture the macro to check for PSE is hard-wired to always be true.

Not in current kernels.

Third, hugepages in Linux makes no check whatsoever for the presence or absence of PSE. It assumes it's there.

Not in current kernels. But it does assume that if PSE is present, then physical memory can always be mapped with large pages.

I'll look into the simplest way to make the various Linux parts obey the PSE flag properly.

No, use a current mainline git linux kernel.

   J

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