arm64: Do not defer reserve_crashkernel() for platforms with no DMA memory zones

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The following patches resulted in deferring crash kernel reservation to
mem_init(), mainly aimed at platforms with DMA memory zones (no IOMMU),
in particular Raspberry Pi 4.

commit 1a8e1cef76 ("arm64: use both ZONE_DMA and ZONE_DMA32")
commit 8424ecdde7 ("arm64: mm: Set ZONE_DMA size based on devicetree's dma-ranges")
commit 0a30c53573 ("arm64: mm: Move reserve_crashkernel() into mem_init()")
commit 2687275a58 ("arm64: Force NO_BLOCK_MAPPINGS if crashkernel reservation is required")

Above changes introduced boot slowdown due to linear map creation for
all the memory banks with NO_BLOCK_MAPPINGS, see discussion[1].  The proposed
changes restore crash kernel reservation to earlier behavior thus avoids
slow boot, particularly for platforms with IOMMU (no DMA memory zones).

Tested changes to confirm no ~150ms boot slowdown on our SoC with IOMMU
and 8GB memory.  Also tested with ZONE_DMA and/or ZONE_DMA32 configs to confirm
no regression to deferring scheme of crash kernel memory reservation.
In both cases successfully collected kernel crash dump.

[1] https://lore.kernel.org/all/9436d033-579b-55fa-9b00-6f4b661c2dd7@linux.microsoft.com/

Signed-off-by: Vijay Balakrishna <vijayb@linux.microsoft.com>
Cc: stable@vger.kernel.org
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Link: https://lore.kernel.org/r/1646242689-20744-1-git-send-email-vijayb@linux.microsoft.com
[will: Add #ifdef CONFIG_KEXEC_CORE guards to fix 'crashk_res' references in allnoconfig build]
Signed-off-by: Will Deacon <will@kernel.org>

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This commit is contained in:

Vijay Balakrishna 2022-03-02 09:38:09 -08:00 • committed by Will Deacon

parent 614c0b9fee

commit 031495635b

2 changed files with 63 additions and 5 deletions

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36

arch/arm64/mm/init.c

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32

arch/arm64/mm/mmu.c

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