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    SubjectRe: [PATCH 0/5] x86_64 EFI support -v3
    From
    Date
    ebiederm@xmission.com (Eric W. Biederman) writes:
    >
    > Since there are people actively investigating things like booting
    > OpenBSD via kexec things get even worse. Nothing hardly runs
    > on ia64 so that issue doesn't come up.

    If you want to do a popularity contest I expect there are far more ia64
    linux users than kexec-of-openbsd users.

    > As for not using EFI at all. If we can avoid it/not use it in the
    > dump kernel there is very little point in having it in the primary
    > kernel.

    One interesting area is to use it for saving oops data. But
    that has to be simple. I'm not sure complicated context switches
    are a good idea here.

    However I agree it probably doesn't make sense to do virtual
    mode just for the clock services -- so far we seem to be fine
    just talking to the hardware directly.

    > So far there don't seem to be any compelling advantages to running
    > EFI in virtual address mode and several compelling disadvantages
    > included having to change the permissions on the kernels memory
    > map to running EFI in virtual mode.

    I don't think it's a big issue to have a few less NX bits. Just
    the original patch for it was ugly.

    > Please let's stick to a physical mode trampoline and only revisit
    > the topic when users start having problems because of the performance
    > hit of going through our trampoline to the EFI runtime services.

    So you want to switch to new page tables when calling EFI services
    after boot?

    Potential problems:
    - Interrupts have to be disabled. Is that ok?
    - When EFI BIOS start crashing how do we set up exception handlers
    for this?

    I guess it would get complex long term. Also doesn't really sound
    attractive.

    -Andi
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