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Date:   Wed, 15 Jun 2022 11:52:00 +0800
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Subject: Re: [PATCH v5 0/5] introduce mirrored memory support for arm64
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To:     Wupeng Ma <mawupeng1@huawei.com>, <corbet@lwn.net>,
        <will@kernel.org>, <ardb@kernel.org>, <catalin.marinas@arm.com>
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References: <20220614092156.1972846-1-mawupeng1@huawei.com>
From:   Kefeng Wang <wangkefeng.wang@huawei.com>
In-Reply-To: <20220614092156.1972846-1-mawupeng1@huawei.com>
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On 2022/6/14 17:21, Wupeng Ma 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.
>
> These EFI memory regions have various attributes, and the "mirrored"
> attribute is one of them. The physical memory region whose descriptors
> in EFI memory map has EFI_MEMORY_MORE_RELIABLE attribute (bit: 16) are
> mirrored. The address range mirroring feature of the kernel arranges such
> mirrored regions into normal zones and other regions into movable zones.
>
> Arm64 can support this too. So mirrored memory support is added to support
> arm64.
>
> The main purpose of this patch set is to introduce mirrored support for
> arm64 and we have already fixed the problems we had which is shown in
> patch #5 to patch #8 and try to bring total isolation in patch #9 which
> will disable mirror feature if kernelcore is not specified.
>
> In order to test this support in arm64:
> - patch this patch set
> - add kernelcore=mirror in kernel parameter
> - start you kernel
>
> Patch #1 introduce mirrored memory support form arm64.
> Patch #2-#4 fix some bugs for arm64 if memory reliable is enabled.
> Patch #5 disable mirror feature if kernelcore is not specified.
>
> Thanks to Ard Biesheuvel's hard work [1], now kernel will perfer mirrored
> memory if kaslr is enabled.
>
> [1] https://lore.kernel.org/linux-arm-kernel/CAMj1kXEPVEzMgOM4+Yj6PxHA-jFuDOAUdDJSiSxy_XaP4P7LSw@mail.gmail.com/T/

For series,

Reviewed-by: Kefeng Wang<wangkefeng.wang@huawei.com>

>
> Changelog since v4:
> - merge the first two patches into one
> - change __initdata to __initdata_memblock in patch #5
>
> Changelog since v3:
> - limit warning message in vmemmap_verify via pr_warn_once()
> - only clear memblock_nomap flags rather than bring the mirrored flag back
> - disable mirrored feature in memblock_mark_mirror()
>
> Changelog since v2:
> - remove efi_fake_mem support
> - remove Commit ("remove some redundant code in ia64 efi_init") since
>    efi_print_memmap() is not public
> - add mirror flag back on initrd memory
>
> Changelog since v1:
> - update changelog in cover letter
> - use PHYS_PFN in patch #7
>
> Ma Wupeng (5):
>    efi: arm64: Introduce ability to find mirrored memory ranges
>    mm: Ratelimited mirrored memory related warning messages
>    mm: Limit warning message in vmemmap_verify() to once
>    arm64: mm: Only remove nomap flag for initrd
>    memblock: Disable mirror feature if kernelcore is not specified
>
>   arch/arm64/mm/init.c            |  2 +-
>   arch/x86/include/asm/efi.h      |  4 ----
>   arch/x86/platform/efi/efi.c     | 23 -----------------------
>   drivers/firmware/efi/efi-init.c |  1 +
>   drivers/firmware/efi/efi.c      | 23 +++++++++++++++++++++++
>   include/linux/efi.h             |  3 +++
>   mm/internal.h                   |  2 ++
>   mm/memblock.c                   |  7 +++++--
>   mm/page_alloc.c                 |  2 +-
>   mm/sparse-vmemmap.c             |  2 +-
>   10 files changed, 37 insertions(+), 32 deletions(-)
>