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    Subject2.6.25-rc1 xen pvops regression
    Hi all,

    I thought I'd try out 2.6.25-rc1 as a xen 32-bit pae domU the other day.
    Unfortunately, I didn't get very far very fast, as the domain just crashed
    immediately upon booting, without any direct feedback (I did have messages
    on the xen message buffer, which helped). This even with earlyprintk turned on.

    After a long, arduous journey, I managed to track this down to the following:

    ----------
    commit 551889a6e2a24a9c06fd453ea03b57b7746ffdc0

    x86: construct 32-bit boot time page tables in native format.

    Specifically the boot time page tables in a CONFIG_X86_PAE=y enabled
    kernel are in PAE format.

    early_ioremap is updated to use the standard page table accessors.

    Clear any mappings beyond max_low_pfn from the boot page tables in
    native_pagetable_setup_start because the initial mappings can extend
    beyond the range of physical memory and into the vmalloc area.

    Derived from patches by Eric Biederman and H. Peter Anvin.

    [ jeremy@goop.org: PAE swapper_pg_dir needs to be page-sized fix ]
    ----------

    However, to make life more interesting, just reverting this isn't quite
    enough to get us to the promised land. If we try, we find that although
    we do now start booting, we crash again a short way into the process.

    In a different manner though. Specifically, in early_ioremap_clear.
    Reverting the above commit /except/ for the changes to arch/x86/mm/ioremap.c
    gets everything working again.

    Well, except that we can't shutdown/reboot properly, but I've sent a patch
    for that in another email.


    I'm afraid i've no idea what needs to be done to get the change to work
    with xen, but i'm willing to try out any patches people come up with.
    Please cc me on any replies, as i'm not subscribed, thanks.


    J
    --
    Jody Belka
    knew (at) pimb (dot) org


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