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    SubjectRe: [Bug Fix]: Do 32-bit table calculations in pre-processor
    Date
    On Fri July 3 2009, H. Peter Anvin wrote:
    > Michael S. Zick wrote:
    > >>
    > >> The PGTABLE reservation seems much too big. I think 1 page should be
    > >> sufficient for a system with large pages. Even if not, 0x6d000 is way
    > >> too large. And they symptoms of failing to reserve the initial
    > >> pagetable are pretty non-subtle.
    > >>
    > >
    > > Random system halts, deadlocks with interrupts disabled?
    > > Yup, that sounds familiar.
    > >
    > > If I ever get more than a stopped machine with a glowing power light;
    > > I will be certain to share.
    > >
    >
    > Let's see... on a non-PSE system we may need one PDE and one PTE page
    > per 4 MB, up to 1 GB, for a total of 256 pages or 1 MB of memory, so in
    > that sense 0x6d000 (109 pages) doesn't sound at all unreasonable
    > (non-PSE system with 512 MB of RAM?)
    >
    > However, we shouldn't have to do this kind of hacks with
    > MAPPING_BEYOND_END, and we *certainly* shouldn't do it by implicitly
    > hard-coding the value of PAGE_SHIFT.
    >

    The calculation was correct - this thread title is a false alarm.

    The difference posted was caused by disabling the "has pae" in the
    build configuration system.
    So I just need to dig around in head.S a bit more - get rid of the
    "Intel Only" hard coding, check if the pae bit is a hardwired zero
    in cr4, make sure I have a usable stack before the testing - since
    the test may generate a GP fault. . .
    Get the in-memory copy of the cpu feature flags correct (some are
    defined but not implemented on this processor). . .
    Then find and fix everything that isn't using 'cpu_has(x, y)' -

    That should keep me busy for a few weeks. ;)

    Mike
    > -hpa
    >




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