[fedora-virt] Re: [PATCH] xen: do not set NX bit when making initial pagetables readonly

Ian Campbell Ian.Campbell at citrix.com
Fri Jan 30 19:07:57 UTC 2009

On Fri, 2009-01-30 at 10:56 -0800, Jeremy Fitzhardinge wrote:
> Ian Campbell wrote:
> > __supported_pte_mask has not been correctly configured at this point
> > and Xen prevents us from using the NX bit if the hardware does not
> > support it. Some BIOSes seem to offer the option to disable NX.
> >   
> Could we sniff EFER and update __supported_pte_mask accordingly?

Perhaps, we might also have to handle the various noexec= command line
options? I don't suppose they matter so much in a guest though.

The equivalent native seems to use _KERNPG_TABLE as well (e.g.
head_64.S) -- is there something later on which comes along and tries to
apply the NX bit to those pages which didn't get it at start of day?


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