On Thu, 2005-08-18 at 16:09 +0100, Keir Fraser wrote:
> 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!
If I remember correctly (will create a patch shortly to make 100% sure).
If the option is off in the BIOS than NX bit will not show up as a CPU
feature flag. And of course once it's on in the bios then it does.
> 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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