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    SubjectRe: [PATCH v2 1/2] x86/efi: don't allocate memmap through memblock after mm_init()
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    Matt Fleming <matt@codeblueprint.co.uk> writes:

    > On Thu, 22 Dec, at 11:23:39AM, Nicolai Stange wrote:
    >> So, after memblock is gone, allocations should be done through the "normal"
    >> page allocator. Introduce a helper, efi_memmap_alloc() for this. Use
    >> it from efi_arch_mem_reserve() and from efi_free_boot_services() as well.
    >>
    >> Fixes: 4bc9f92e64c8 ("x86/efi-bgrt: Use efi_mem_reserve() to avoid copying image data")
    >> Signed-off-by: Nicolai Stange <nicstange@gmail.com>

    > Could you also modify efi_fake_memmap() to use your new
    > efi_memmap_alloc() function for consistency

    Sure.

    I'm planning to submit another set of patches addressing the (bounded)
    memmap leaking in anything calling efi_memmap_unmap() though. In the
    course of doing so, the memmap allocation sites will get touched anyway:
    I'll have to store some information about how the memmap's memory has
    been obtained.

    > (note that all memblock_alloc()s should probably be PAGE_SIZE aligned
    > like the fakemem code)?

    Ok, but I'd really like to understand why: I can't find anything in
    neither the code nor in the UEFI spec requiring this. And up to now,
    efi_arch_mem_reserve() as well as efi_free_boot_services() used to do
    those unaligned allocations...

    In light of this, is there really a necessity for using whole page
    allocations after mm_init() or would kmalloc() suffice here?
    Provided that the memremap bits get adjusted accordingly, of course.

    So, I'm thinking of turning the ->late boolean into a tristate like the
    following:

    Memory allocated by | Memory mapped through
    --------------------|----------------------
    memblock | early_memremap
    memblock | memremap
    kmalloc | -

    Neglecting slub overhead, the use of kmalloc() over alloc_pages() would
    save 4096 - 12*40 == 3616 Bytes on my system with its 12 entries under
    /sys/firmware/efi/runtime-map/. Not really critical, but if it comes for
    free, why not?


    Thanks,

    Nicolai

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