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Re: [Xen-devel] Re: Oops when loading xen_platform_pci module in HVM dom

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] Re: Oops when loading xen_platform_pci module in HVM domain on CS 11429
From: Steven Smith <sos22-xen@xxxxxxxxxxxxx>
Date: Fri, 8 Sep 2006 18:03:10 +0100
Cc: Steve Dobbelstein <steved@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, sos22@xxxxxxxxxxxxx
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> > I tried hacking some code to turn off the NX bit in the PTE for the
> > hypercall stubs page, but I still get the oops.  I'm thinking it's because
> > the NX bit is set in the PMD.
> > 
> > I'm quite new to the paging mechanism, so I'm not sure how to fix this at
> > the moment.   I'll keep poking around.  thought I'd share my findings so
> > far.
> Page directory entries use permissions _PAGE_TABLE, which does not include
> _PAGE_NX. So clearing _PAGE_NX from the PTEs, using
> change_page_attr(PAGE_KERNEL_EXEC), should suffice.
The oops message is fairly clear that _PAGE_NX is set on the PMD, and
I'd guess it probably got set from phys_pmd_init.

I think vmalloc_exec is probably the right answer here.  I'll have a
go at this over the weekend.

Steven.

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