Re: [Xen-devel] Re: what's the purpose of linear page table (PML4 entry 258)

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 14:15 -0400 on 31 Mar (1206972951), weiming wrote:
> I find that it give the same pte value as I manually walking the 4 level
> page table directory.
> So I guest it facilitates the locating of a pte from va. It removes the
> 4-level looking up process: pgd->pud->pmd->pt->pte
> It saves time. Am I right?

IIRC, it just does that walk internally and hands back the answer.  I
don't recall off the top of my head why Michael introduced it except
that it was necessary for shadowing some kinds of PV guests.  It may
have been to do with the way the shadow-pagetable spinlocks used to
work.

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Citrix Systems (R&D) Ltd.
[Company #02300071, SL9 0DZ, UK.]

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