Re: x86-64 machine_to_phys vs NX bit

[John Byrne <john.l.byrne@hp.com>]

Keir Fraser wrote:
> On 13/11/06 8:07 am, "Jan Beulich" <jbeulich@novell.com> wrote:
> 
>>> There was a bug in my previous patch. (There's nothing like trying to
>>> get to sleep and realizing you've screwed up.) The x86 pae
>>> PHYSICAL_PAGE_MASK I defined was incorrect because PAGE_MASK was only a
>>> long. I hope I haven't done anything else wrong.
>> I don't think this is correct - machine_to_phys() translates a machine address
>> to a physical one, and in that translation the upper bits matter only as much
>> as mfn_to_pfn() should return an invalid indicator if any of them is set. In
>> turn,
>> it should be the caller's responsibility to make sure the NX bit (and any
>> potential
>> other one being set beyond bit 52) gets masked off *before* calling this
>> function. (Specifically, the preserving of the lower bits is to properly
>> translate
>> a non-page aligned address, not to preserve attribute bits read from a page
>> table entry).
> 
> Yes, we should keep the old machine_to_phys() definition and rename John's
> new version as pte_machine_to_phys(). The latter should be used in all
> contexts where machine_to_phys() currently operates on a pte (that's most of
> its uses, actually). This is a worthwhile cleanup and clarification. Could
> you respin the patch, John?
> 
>  Thanks,
>  Keir
> 
> 
> 

I've  made the change. I'll send it out after I've built and tested it.

John