Re: [Xen-devel] [PATCH] supporting non-NX/XD capable processors on x86_64 xenlinux

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 18 Aug 2005, at 15:15, Nakajima, Jun wrote:

> One obvious reason is: xen-specific drivers are using __PAGE_KERNEL 
> (and
> they don't exist in the native Linux). If xen_contig_memory, for
> example, does not work, it won't boot... Fixing xen_contig_memory did
> not fix the booting problem as long as I remember?
Yeah, I see what you mean. I've just applied a patch that cleans up the 
few remaining bad spots where we weren't using pfn_pte() or 
pfn_pte_ma() constructors. I can now boot okay even with NX/XD disabled 
in Xen.
By the way -- from what I've seen of this NX/XD discussion so far, it 
sounds like even if CPUID says that NX/XD is supported, and you set the 
EFER.NXE bit, the BIOS can still cause this to be ignored! Is this true 
and, if so, what will happen if you try to use NX/XD anyway? i.e., will 
the bit be ignored, or will its use cause a page fault?
 -- Keir


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