Messages in this thread | | | Date | Thu, 11 May 2023 16:47:13 +0800 | Subject | Re: [PATCH -next v4 1/2] riscv: kdump: Implement crashkernel=X,[high,low] | From | "chenjiahao (C)" <> |
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On 2023/4/27 10:13, Baoquan He wrote: > On 04/10/23 at 09:05pm, Chen Jiahao 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. >> Here introduce 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". >> >> Signed-off-by: Chen Jiahao <chenjiahao16@huawei.com> >> Acked-by: Guo Ren <guoren@kernel.org> >> Reviewed-by: Zhen Lei <thunder.leizhen@huawei.com> >> --- >> arch/riscv/kernel/setup.c | 5 +++ >> arch/riscv/mm/init.c | 71 ++++++++++++++++++++++++++++++++++++--- >> 2 files changed, 71 insertions(+), 5 deletions(-) >> >> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c >> index 5d3184cbf518..ea84e5047c23 100644 >> --- a/arch/riscv/kernel/setup.c >> +++ b/arch/riscv/kernel/setup.c >> @@ -176,6 +176,11 @@ static void __init init_resources(void) >> if (ret < 0) >> goto error; >> } >> + if (crashk_low_res.start != crashk_low_res.end) { >> + ret = add_resource(&iomem_resource, &crashk_low_res); >> + if (ret < 0) >> + goto error; >> + } >> #endif >> >> #ifdef CONFIG_CRASH_DUMP >> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c >> index 478d6763a01a..70f6cb281ed1 100644 >> --- a/arch/riscv/mm/init.c >> +++ b/arch/riscv/mm/init.c >> @@ -1152,6 +1152,28 @@ static inline void setup_vm_final(void) >> } >> #endif /* CONFIG_MMU */ >> >> +/* Reserve 128M low memory by default for swiotlb buffer */ >> +#define DEFAULT_CRASH_KERNEL_LOW_SIZE (128UL << 20) >> + >> +static int __init reserve_crashkernel_low(unsigned long long low_size) >> +{ >> + unsigned long long low_base; >> + >> + low_base = memblock_phys_alloc_range(low_size, PMD_SIZE, 0, dma32_phys_limit); >> + if (!low_base) { >> + pr_err("cannot allocate crashkernel low memory (size:0x%llx).\n", low_size); >> + return -ENOMEM; >> + } >> + >> + pr_info("crashkernel low memory reserved: 0x%016llx - 0x%016llx (%lld MB)\n", >> + low_base, low_base + low_size, low_size >> 20); >> + >> + crashk_low_res.start = low_base; >> + crashk_low_res.end = low_base + low_size - 1; >> + >> + return 0; >> +} >> + >> /* >> * reserve_crashkernel() - reserves memory for crash kernel >> * >> @@ -1163,8 +1185,12 @@ static void __init reserve_crashkernel(void) >> { >> unsigned long long crash_base = 0; >> unsigned long long crash_size = 0; >> + unsigned long long crash_low_size = 0; >> unsigned long search_start = memblock_start_of_DRAM(); >> unsigned long search_end = memblock_end_of_DRAM(); >> + unsigned long search_low_max = (unsigned long)dma32_phys_limit; >> + char *cmdline = boot_command_line; >> + bool fixed_base = false; >> >> int ret = 0; >> >> @@ -1180,14 +1206,34 @@ static void __init reserve_crashkernel(void) >> return; >> } >> >> - ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(), >> + ret = parse_crashkernel(cmdline, memblock_phys_mem_size(), >> &crash_size, &crash_base); >> - if (ret || !crash_size) >> + if (ret == -ENOENT) { >> + /* Fallback to crashkernel=X,[high,low] */ >> + ret = parse_crashkernel_high(cmdline, 0, &crash_size, &crash_base); >> + if (ret || !crash_size) >> + return; >> + >> + /* >> + * crashkernel=Y,low is valid only when crashkernel=X,high >> + * is passed. >> + */ >> + ret = parse_crashkernel_low(cmdline, 0, &crash_low_size, &crash_base); >> + if (ret == -ENOENT) >> + crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE; >> + else if (ret) >> + return; >> + >> + search_start = search_low_max; >> + } else if (ret || !crash_size) { >> + /* Invalid argument value specified */ >> return; >> + } >> >> crash_size = PAGE_ALIGN(crash_size); >> >> if (crash_base) { >> + fixed_base = true; >> search_start = crash_base; >> search_end = crash_base + crash_size; >> } >> @@ -1201,16 +1247,31 @@ static void __init reserve_crashkernel(void) >> */ >> crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE, >> search_start, >> - min(search_end, (unsigned long) SZ_4G)); >> + min(search_end, search_low_max)); > Here, it seems not right in case crashkernel=,high is specified. In that > case, search_start == search_low_max, then the min(search_end, > search_low_max) will get search_low_max too. Then you make the fallback > in below code block to try to get crashkernel reservation above 4G. This > doesn't comply with the crashkernel=,high grammer which has been > implemented in other architectures. > > For crashkernel=,high, user explicitly require memory reservation above > 4G. Why does crashkernel=,high is needed? E.g on big end server with > huge memory, while the low memory under 4G is limited and precious. > Hence, user want to put the main crashkernel reservation above 4G to > contain kdump kernel/initrd and run user space program, while with few > low memory for pci device driver. E.g crashkernel=2G,high, it won't > impact much if there's huge memory above 4G and get crashkernel > reservation there. However, it impacts a lot if it reserves memory > below 4G. > > I would strongly suggest that risc-v also reserve memory from above 4G > for crashkernel=,high, then fallback to below 4G. That's consistent with > crashkernel=,high grammer.
Sorry for late response.
I have got the point here. So with the original implication of "crashkernel=,high", there is even no need to try reserving low memory under 4G. I have arranged another version of patchset, in which I updated the allocation logic in that case.
For example, when "crashkernel=1G,high" is specified, the previous logic is like: alloc range: crash_size: 0x40000000 (1G), crash_base: 4G_limit, crash_max: 4G_limit alloc range high: crash_size: 0x40000000 (1G), crash_base: 4G_limit, crash_max: memblock_range_end alloc range low: low_size: 0x8000000 (128MB,default), crash_base: 0x0, crash_max: 4G_limit
After revision, the logic is like: alloc range: crash_size: 0x40000000 (1G), crash_base: memblock_range_start, crash_max: memblock_range_end alloc range low: low_size: 0x8000000 (128MB,default), crash_base: 0x0, crash_max: 4G_limit
Please let me know if there is any problem exist.
Thanks, Jiahao
> >> if (crash_base == 0) { >> - /* Try again without restricting region to 32bit addressible memory */ >> + if (fixed_base) { >> + pr_warn("crashkernel: allocating failed with given size@offset\n"); >> + return; >> + } >> + >> + /* Try again above the region of 32bit addressible memory */ >> crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE, >> - search_start, search_end); >> + max(search_start, search_low_max), >> + search_end); >> if (crash_base == 0) { >> pr_warn("crashkernel: couldn't allocate %lldKB\n", >> crash_size >> 10); >> return; >> } >> + >> + if (!crash_low_size) >> + crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE; >> + } >> + >> + if ((crash_base > dma32_phys_limit - crash_low_size) && >> + crash_low_size && reserve_crashkernel_low(crash_low_size)) { >> + memblock_phys_free(crash_base, crash_size); >> + return; >> } >> >> pr_info("crashkernel: reserved 0x%016llx - 0x%016llx (%lld MB)\n", >> -- >> 2.31.1 >>
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