On Mon, Jul 3, 2023 at 9:07 PM chenjiahao (C) <chenjiahao16@xxxxxxxxxx> wrote: > > > On 2023/7/1 21:45, Guo Ren wrote: > > On Sat, Jul 1, 2023 at 5:12 PM Chen Jiahao <chenjiahao16@xxxxxxxxxx> wrote: > >> On riscv, the current crash kernel allocation logic is trying to > >> 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 > > Have you tried 1GB memory? we found a pud mapping problem on Sv39 of kexec, See: > > https://lore.kernel.org/linux-riscv/20230629082032.3481237-1-guoren@xxxxxxxxxx/ > > I have tested on QEMU with sv57 mmu, so it seems the synchronization problem > was not reproduce when reserving 1G memory and loading the capture kernel. Yes, the pud of sv57 is not the pgd entries, so you didn't get problem. > > > Thanks, > Jiahao > > > > >> 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 > >> > > -- Best Regards Guo Ren
