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    SubjectRe: [PATCH v2 0/9] introduce mirrored memory support for arm64
    On Thu, 14 Apr 2022 at 11:54, Wupeng Ma <mawupeng1@huawei.com> wrote:
    >
    > From: Ma Wupeng <mawupeng1@huawei.com>
    >
    > Commit b05b9f5f9dcf ("x86, mirror: x86 enabling - find mirrored memory ranges")
    > introduced mirrored memory support for x86. This support rely on UEFI to
    > report mirrored memory address ranges. See UEFI 2.5 spec pages 157-158:
    >
    > http://www.uefi.org/sites/default/files/resources/UEFI%202_5.pdf
    >
    > Memory mirroring is a technique used to separate memory into two separate
    > channels, usually on a memory device, like a server. In memory mirroring,
    > one channel is copied to another to create redundancy. This method makes
    > input/output (I/O) registers and memory appear with more than one address
    > range because the same physical byte is accessible at more than one
    > address. Using memory mirroring, higher memory reliability and a higher
    > level of memory consolidation are possible.
    >
    > Arm64 can support this too. So mirrored memory support is added to support
    > arm64.
    >
    > Efi_fake_mem is used for testing mirrored features and will not be used in
    > production environment. This test features can fake memory's attribute
    > values.
    >
    > The reason why efi_fake_mem support is put first is that memory's attribute
    > is reported by BIOS which is hard to simulate. With this support, any arm64
    > machines with efi support can easily test mirrored features.
    >
    > The main purpose of this patchset is to introduce mirrored support for
    > arm64 and we have already fixed the problems we had which is shown in
    > patch #5 to patch #7 and try to bring total isolation in patch #8 which
    > will disable mirror feature if kernelcore is not specified.
    >
    > In order to test this support in arm64:
    > - patch this patchset
    > - add efi_fake_mem=8G@0:0x10000 in kernel parameter to simulate mirrored
    > memroy between phy addr 0-8G.
    > - add kernelcore=mirror in kernel parameter
    > - start you kernel
    >

    As I explained before:

    - NAK to EFI fake_mem support on arm64
    - NAK to the whole series until you come up with a proposal on how to
    locate the static kernel image itself into more reliable memory, as
    there is really no point to any of this otherwise.

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