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    SubjectRe: [PATCH 2/2] arm64/efi: Don't pad between EFI_MEMORY_RUNTIME regions
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    On 09/27/2015 12:06 AM, Ingo Molnar wrote:
    >
    > * Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
    >
    >>> If we allocate the EFI runtime as a single virtual memory block then issues
    >>> like rounding between sections does not even come up as a problem: we map the
    >>> original offsets and sizes byte by byte.
    >>
    >> Well, by that reasoning, we should not call SetVirtualAddressMap() in the first
    >> place, and just use the 1:1 mapping UEFI uses natively. This is more than
    >> feasible on arm64, and I actually fought hard against using
    >> SetVirtualAddressMap() at all, but I was overruled by others. I think this is
    >> also trivially possible on X64, since the 1:1 mapping is already active
    >> alongside the VA mapping.
    >
    > Could we please re-list all the arguments pro and contra of 1:1 physical mappings,
    > in a post that also explains the background so that more people can chime in, not
    > just people versed in EFI internals? It's very much possible that a bad decision
    > was made.
    >

    Pro: by far the sanest way to map the UEFI tables.
    Con: doesn't actually work (breaks on several known platforms.)

    -hpa




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