Re: [Xen-devel] x86-64 machine_to_phys vs NX bit

[Rik van Riel <riel@xxxxxxxxxx>]

Keir Fraser wrote:
> On 24/8/06 8:25 pm, "Rik van Riel" <riel@xxxxxxxxxx> wrote:
>
> > Say, something like the following?
> >
> > -    paddr_t phys = mfn_to_pfn(machine >> PAGE_SHIFT);
> > +    paddr_t phys = mfn_to_pfn((machine >> PAGE_SHIFT) & PHYSICAL_MASK);
> >
> > I'm still thinking I may have missed something in the code
> > somewhere, but I've been looking at this for over an hour now
> > and can't seem to find it...
> >
> > Any ideas?
> Your suggested patch looks reasonable but it'd be good to find out why this
> hasn't caused us problems. For example, perhaps supported_pte_mask doesn't
> include PAGE_NX, so we're never setting the NX bit on 64-bit PTEs?
We do set the NX bit.  Including on vmalloced pages...

> That must be worth checking out, possibly also tracing 
> machine_to_phys to find out where that bit 63 goes -- I agree that it
> looks like mfn_to_pfn() shouldn't work if bit63 is set in the
> 'maddr' argument.
Absolutely :)

--
What is important?  What you want to be true, or what is true?

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