Messages in this thread | | | From | Nicolai Stange <> | Subject | Re: [PATCH v2 1/2] x86/efi: don't allocate memmap through memblock after mm_init() | Date | Fri, 23 Dec 2016 22:12:21 +0100 |
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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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