On Sat, Jul 1, 2023 at 5:12 PM Chen Jiahao <chenjiahao16@xxxxxxxxxx> wrote:
On riscv, the current crash kernel allocation logic is trying toHave you tried 1GB memory? we found a pud mapping problem on Sv39 of kexec, See:
allocate within 32bit addressible memory region by default, if
failed, try to allocate without 4G restriction.
In need of saving DMA zone memory while allocating a relatively large
crash kernel region, allocating the reserved memory top down in
high memory, without overlapping the DMA zone, is a mature solution.
Hence this patchset introduces the parameter option crashkernel=X,[high,low].
One can reserve the crash kernel from high memory above DMA zone range
by explicitly passing "crashkernel=X,high"; or reserve a memory range
below 4G with "crashkernel=X,low". Besides, there are few rules need
to take notice:
1. "crashkernel=X,[high,low]" will be ignored if "crashkernel=size"
is specified.
2. "crashkernel=X,low" is valid only when "crashkernel=X,high" is passed
and there is enough memory to be allocated under 4G.
3. When allocating crashkernel above 4G and no "crashkernel=X,low" is
specified, a 128M low memory will be allocated automatically for
swiotlb bounce buffer.
See Documentation/admin-guide/kernel-parameters.txt for more information.
To verify loading the crashkernel, adapted kexec-tools is attached below:
https://github.com/chenjh005/kexec-tools/tree/build-test-riscv-v2
Following test cases have been performed as expected:
1) crashkernel=256M //low=256M
2) crashkernel=1G //low=1G
https://lore.kernel.org/linux-riscv/20230629082032.3481237-1-guoren@xxxxxxxxxx/
3) crashkernel=4G //high=4G, low=128M(default)
4) crashkernel=4G crashkernel=256M,high //high=4G, low=128M(default), high is ignored
5) crashkernel=4G crashkernel=256M,low //high=4G, low=128M(default), low is ignored
6) crashkernel=4G,high //high=4G, low=128M(default)
7) crashkernel=256M,low //low=0M, invalid
8) crashkernel=4G,high crashkernel=256M,low //high=4G, low=256M
9) crashkernel=4G,high crashkernel=4G,low //high=0M, low=0M, invalid
10) crashkernel=512M@0xd0000000 //low=512M
Changes since [v6]:
1. Introduce the "high" flag to mark whether "crashkernel=X,high"
is passed. Fix the retrying logic between "crashkernel=X,high"
case and others when the first allocation attempt fails.
Changes since [v5]:
1. Update the crashkernel allocation logic when crashkernel=X,high
is specified. In this case, region above 4G will directly get
reserved as crashkernel, rather than trying lower 32bit allocation
first.
Changes since [v4]:
1. Update some imprecise code comments for cmdline parsing.
Changes since [v3]:
1. Update to print warning and return explicitly on failure when
crashkernel=size@offset is specified. Not changing the result
in this case but making the logic more straightforward.
2. Some minor cleanup.
Changes since [v2]:
1. Update the allocation logic to ensure the high crashkernel
region is reserved strictly above dma32_phys_limit.
2. Clean up some minor format problems.
Chen Jiahao (2):
riscv: kdump: Implement crashkernel=X,[high,low]
docs: kdump: Update the crashkernel description for riscv
.../admin-guide/kernel-parameters.txt | 15 ++--
arch/riscv/kernel/setup.c | 5 ++
arch/riscv/mm/init.c | 84 +++++++++++++++++--
3 files changed, 90 insertions(+), 14 deletions(-)
--
2.34.1