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    SubjectRe: [CFT][PATCH] 2.6.4-rc1 remove x86 boot page tables
    Date (H. Peter Anvin) writes:

    > Followup to: <>
    > By author: (Eric W. Biederman)
    > In newsgroup:
    > >
    > > I think I have accounted for the sub architectures but I don't have
    > > the hardware to test them. For voyager and VISWS I actually changed
    > > some code so I would appreciate a confirmation I didn't break
    > > anything.
    > >
    > For VISWS I think you actually need to turn paging off explicitly.

    Hmm. I will look at that.

    > Also, you probably need to check that you didn't break 4G/4G,
    > especially on SMP.

    The patch will need a few tweaks but it should be fairly straight forward.

    > I would also like to remove the magic %bx, which I did in the version
    > of my patch sent to akpm and which is now in -mm (basically the SMP
    > trampoline jumps to a different entrypoint instead.) In that patch,
    > %ebx is still used as a flag, but it's completely internal to head.S.

    Ok I have not seen that one. In this case there was enough common
    code that it seemed reasonable to reuse it. I managed to reduce
    the code to two tests. With just a bit of care I suspect I could
    remove the tests completely.

    > See
    > > Thanks to HPA who got the ball started :)
    > :)
    > I definitely agree that simply using no paging until we have page
    > tables is by far the cleanest approach. I felt that is was too high
    > risk for 2.6, basically because I'm a chicken, but more realistically
    > because I couldn't really see the effect on all subarchitectures, and
    > I didn't feel 100% confident that there wasn't anything that relied on
    > memory being dual mapped; however, I'm more than happy to be proven
    > wrong :)

    I will try. So far except for early_printk I have not found anything.
    And that was easy to fix.

    > Oh yes, with this change you should probably just move swapper_pg_dir
    > (and empty_zero_page?) into .bss like anything else that should be
    > zero after boot.

    Sounds like a good idea.

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