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docs: kdump: Update the crashkernel description for riscv

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Now "crashkernel=" parameter on riscv has been updated to support
crashkernel=X,[high,low]. Through which we can reserve memory region
above/within 32bit addressible DMA zone.

Here update the parameter description accordingly.

Signed-off-by: Chen Jiahao <chenjiahao16@huawei.com>
Reviewed-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Zhen Lei <thunder.leizhen@huawei.com>
Acked-by: Baoquan He <bhe@redhat.com>
Link: https://lore.kernel.org/r/20230726175000.2536220-3-chenjiahao16@huawei.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Chen Jiahao 2023-07-26 17:50:00 +00:00 committed by Palmer Dabbelt
parent 5882e5acf1
commit 33f0dd973d
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1 changed files with 8 additions and 7 deletions
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15
Documentation/admin-guide/kernel-parameters.txt
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@ -862,7 +862,7 @@
memory region [offset, offset + size] for that kernel
image. If '@offset' is omitted, then a suitable offset
is selected automatically.
[KNL, X86-64, ARM64] Select a region under 4G first, and
[KNL, X86-64, ARM64, RISCV] Select a region under 4G first, and
fall back to reserve region above 4G when '@offset'
hasn't been specified.
See Documentation/admin-guide/kdump/kdump.rst for further details.
@ -875,14 +875,14 @@
Documentation/admin-guide/kdump/kdump.rst for an example.
crashkernel=size[KMG],high
[KNL, X86-64, ARM64] range could be above 4G. Allow kernel
to allocate physical memory region from top, so could
be above 4G if system have more than 4G ram installed.
Otherwise memory region will be allocated below 4G, if
available.
[KNL, X86-64, ARM64, RISCV] range could be above 4G.
Allow kernel to allocate physical memory region from top,
so could be above 4G if system have more than 4G ram
installed. Otherwise memory region will be allocated
below 4G, if available.
It will be ignored if crashkernel=X is specified.
crashkernel=size[KMG],low
[KNL, X86-64, ARM64] range under 4G. When crashkernel=X,high
[KNL, X86-64, ARM64, RISCV] range under 4G. When crashkernel=X,high
is passed, kernel could allocate physical memory region
above 4G, that cause second kernel crash on system
that require some amount of low memory, e.g. swiotlb
@ -893,6 +893,7 @@
size is platform dependent.
--> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
--> arm64: 128MiB
--> riscv: 128MiB
This one lets the user specify own low range under 4G
for second kernel instead.
0: to disable low allocation.