Messages in this thread | | | Date | Tue, 4 Jul 2023 10:18:01 +0800 | Subject | Re: [PATCH -next v6 1/2] riscv: kdump: Implement crashkernel=X,[high,low] | From | "chenjiahao (C)" <> |
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On 2023/7/2 12:12, Baoquan He wrote: > On 07/01/23 at 05:11pm, 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> >> --- >> arch/riscv/kernel/setup.c | 5 +++ >> arch/riscv/mm/init.c | 84 +++++++++++++++++++++++++++++++++++---- >> 2 files changed, 82 insertions(+), 7 deletions(-) >> >> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c >> index 971fe776e2f8..376f5d49ce85 100644 >> --- a/arch/riscv/kernel/setup.c >> +++ b/arch/riscv/kernel/setup.c >> @@ -178,6 +178,11 @@ 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 4b95d8999120..eeb31c2cc843 100644 >> --- a/arch/riscv/mm/init.c >> +++ b/arch/riscv/mm/init.c >> @@ -1298,6 +1298,28 @@ 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 >> * >> @@ -1309,8 +1331,12 @@ 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_end = (unsigned long)dma32_phys_limit; >> + char *cmdline = boot_command_line; >> + bool fixed_base = false; >> + bool high = false; >> >> int ret = 0; >> >> @@ -1326,14 +1352,36 @@ 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 = (unsigned long)dma32_phys_limit; >> + search_end = memblock_end_of_DRAM(); >> + high = true; >> + } 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; >> } >> @@ -1346,17 +1394,39 @@ static void __init reserve_crashkernel(void) >> * swiotlb can work on the crash kernel. >> */ >> crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE, >> - search_start, >> - min(search_end, (unsigned long) SZ_4G)); >> + search_start, search_end); >> 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; >> + } >> + >> + if (high) { >> + /* Fall back to lower 32G reservation */ >> + search_start = memblock_start_of_DRAM(); >> + search_end = (unsigned long)dma32_phys_limit; >> + } else { >> + /* Try again above the region of 32bit addressible memory */ >> + search_start = (unsigned long)dma32_phys_limit; >> + search_end = memblock_end_of_DRAM(); >> + } >> + >> crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE, >> - search_start, search_end); >> + search_start, 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; > How do you differentiate the case user specifies crashkernel=0M,low > explicitly with the case that user doesn't specify crashkernel=,low, but > only specify crsahkernel=xM,high? I saw you don't have the test case > crashkernel=xM,high crashkernel=0M,low listed in your cover letter.
Yes, here is indeed a point not exactly aligned with Arm64 code. But testcases below seem to have the same result with Arm64:
crashkernel=512M,high //high=512M, low=128M (default) crashkernel=512M,high crashkernel=0M,low //high=512M, low=0M crashkernel=512M,high crashkernel=256M,low //high=512M, low=256M
When the first allocation succeed, it will not fallback into the if (crash_base == 0) case, the allocation result is the same as Arm64, both for explicitly given "crashkernel=0M,low" or not.
The problem you mentioned might occurs when the first allocation failed.
My logic here is when crashkernel=xM,high is specified, no matter crashkernel=0M,low is explicitly given or not, "high" flag is set. It will fallback to lower 4G allocation, additional lower 4G region with "crash_low_size" will never get reserved.
So the results between Arm64 and riscv when crashkernel=,low is specified or not are the same. Is there any problem with my logic, or have I misunderstood your comment above?
> >> + } >> + >> + if ((crash_base >= dma32_phys_limit) && crash_low_size && >> + reserve_crashkernel_low(crash_low_size)) {
Here, additional lower memory region will not reserve when crashkernel=xM,high is given
>> + memblock_phys_free(crash_base, crash_size); >> + return; >> } >> >> pr_info("crashkernel: reserved 0x%016llx - 0x%016llx (%lld MB)\n", >> -- >> 2.34.1 >> Thanks,
Jiahao
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