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    SubjectRe: [PATCH 1/4] efi/x86: make efi_memmap_reserve only insert into boot mem areas
    On 27 January 2017 at 22:13, Matt Fleming <matt@codeblueprint.co.uk> wrote:
    > On Fri, 27 Jan, at 05:04:50PM, Ard Biesheuvel wrote:
    >> On 27 January 2017 at 14:48, Matt Fleming <matt@codeblueprint.co.uk> wrote:
    >> > On Fri, 13 Jan, at 05:29:52AM, Dave Young wrote:
    >> >>
    >> >> It sounds reasonable though I'm still not sure about EFI_LOADER*.
    >> >>
    >> >> The main purpose of this patch is to address the invalid mem ranges
    >> >> case. As Ard mentioned I will test with Peter's patch first, if it works
    >> >> fine I would like to either drop this patch as a future improvement or add
    >> >> it at the end of the next post.
    >> >>
    >> >> Matt, what's your opinion about the boot_only check and the EFI_LOADERS*
    >> >> question?
    >> >
    >> > The main reason that efi_mem_reserve() isn't used for EFI_LOADER
    >> > regions today is because we already have a mechanism for reserving it
    >> > via memblock_reserve(), which we do during a very early stage of boot
    >> > when parsing all the different types of SETUP_* objects.
    >> >
    >> > It's questionable whether it would make sense to switch to
    >> > efi_mem_reserve() for EFI_LOADER regions because then you'd
    >> > potentially have different APIs for different SETUP_* objects.
    >> >
    >> > As things stand today, I would suggest triggering a WARN_ON() if
    >> > someone tries to efi_mem_reserve() an EFI_LOADER region, until/unless
    >> > the day comes when a user exists in the kernel.
    >>
    >> Hmm, I just queued this. Should we drop it again?
    >
    > Does dropping it break the entire series?
    >
    > Having had some time to re-read Dave's commit log, it sounds like it
    > just papers over a bug, which is that efi_memmap_insert() cannot deal
    > with reserved entries, which all look like they describe the same
    > region.
    >

    No, it cannot deal with bogus entries, and Peter already fixed that.
    Dave confirmed that Peter's patch (the one we moved from next to
    urgen) made the problem go away.

    > So I guess my question is: Shouldn't you fix that instead of requiring
    > the caller of efi_memmap_insert() to understand what type of entries
    > it's mapping?

    Indeed. So I don't think the patch is actually needed anymore

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