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    SubjectRe: [PATCH -tip] x86,apic: Use PAGE_SIZE instead of numbers
    On 11/10/09, Maciej W. Rozycki <> wrote:
    > On Mon, 9 Nov 2009, H. Peter Anvin wrote:
    >> In theory we could have more than one ioapic packed into a single page,
    >> and it is also entirely plausible we'll support other page sizes in x86
    >> at some point. However, it's probably easier to flag something as
    >> PAGE_SIZE and have to fix it up later than have magic constants, so I
    >> think it's probably the right thing to do.
    > Hmm, the MPS said in Chapter 3.6.5 "APIC Memory Mapping":
    > "Non-default APIC base addresses can be used if the MP configuration
    > table is provided. (Refer to Chapter 4.) However, the local APIC base
    > address must be aligned on a 4K boundary, and the I/O APIC base address
    > must be aligned on a 1K boundary."
    > This probably still stands; I suppose it would be safer to define
    > IOAPIC_SLOT_SIZE to 1024 and use it by default, expanding all reservations
    > as needed where less than PAGE_SIZE / IOAPIC_SLOT_SIZE I/O APICs would be

    yes, it would be even more clear, i'll take care

    > mapped in a page. This is relatively recent a piece of code -- how much
    > has it been tested?
    > Well, actually not much as a quick search has revealed this message:
    > which shows page alignment of I/O APICs clearly does not stand, and
    > moreover there are two pairs of I/O APIC in the system reported which
    > share a page each. In this case the ranges requested do not make sense
    > and some resource insertions will silently fail. And also while page
    > aliases created in fixmaps here should not harm, they make me feel a
    > little bit chilly...
    > Overall this piece of code needs an overhaul, fixing resource allocation
    > and reusing fixmaps where possible.


    > Maciej

    thanks, Peter, Maciej for comments!
    I must admit (to be fair) i was concerning about fixmap itself so that
    forgot about 1k alignment requirement :/ Will fix.

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