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Date: Thu, 30 Mar 2023 21:40:35 +0800
From: "chenjiahao (C)" <chenjiahao16@...wei.com>
To: Baoquan He <bhe@...hat.com>
CC: <paul.walmsley@...ive.com>, <palmer@...belt.com>,
<conor.dooley@...rochip.com>, <guoren@...nel.org>,
<heiko@...ech.de>, <bjorn@...osinc.com>, <alex@...ti.fr>,
<akpm@...ux-foundation.org>, <atishp@...osinc.com>,
<thunder.leizhen@...wei.com>, <horms@...nel.org>,
<linux-kernel@...r.kernel.org>, <linux-riscv@...ts.infradead.org>,
<kexec@...ts.infradead.org>, <linux-doc@...r.kernel.org>
Subject: Re: [PATCH -next v2 1/2] riscv: kdump: Implement
crashkernel=X,[high,low]
On 2023/3/29 19:19, Baoquan He wrote:
> On 03/28/23 at 07:51pm, Chen Jiahao wrote:
Thanks for reviewing.
>> 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@...wei.com>
>> ---
>> arch/riscv/kernel/setup.c | 5 ++++
>> arch/riscv/mm/init.c | 63 ++++++++++++++++++++++++++++++++++++---
>> 2 files changed, 64 insertions(+), 4 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..b7708cc467fa 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
>> *
>> @@ -1163,6 +1185,7 @@ 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();
>>
>> @@ -1182,8 +1205,30 @@ static void __init reserve_crashkernel(void)
>>
>> ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
>> &crash_size, &crash_base);
>> - if (ret || !crash_size)
>> + if (ret == -ENOENT) {
>> + /*
>> + * crashkernel=X,[high,low] can be specified or not, but
>> + * invalid value is not allowed.
>> + */
>> + ret = parse_crashkernel_high(boot_command_line, 0, &crash_size, &crash_base);
> I would add a local variable to assign boot_command_line to it just like
> arm64 does. Then these lines could be shorter.
>
> char *cmdline = boot_command_line;
Agreed, I will clean this up later in next version.
>> + if (ret || !crash_size)
>> + return;
>> +
>> + /*
>> + * crashkernel=Y,low is valid only when crashkernel=X,high
>> + * is passed and high memory is reserved successful.
>> + */
>> + ret = parse_crashkernel_low(boot_command_line, 0, &crash_low_size, &crash_base);
>> + if (ret == -ENOENT)
>> + crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
>> + else if (ret)
>> + return;
>> +
>> + search_start = dma32_phys_limit;
>> + } else if (ret || !crash_size) {
>> + /* Invalid argument value specified */
>> return;
>> + }
>>
>> crash_size = PAGE_ALIGN(crash_size);
>>
>> @@ -1201,16 +1246,26 @@ 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, (unsigned long)dma32_phys_limit));
>> if (crash_base == 0) {
> The above conditional check isn't right. If crashkernel=size@...set
> specified, the reservation failure won't trigger retry. This seems to be
> originally introduced by old commit, while this need be fixed firstly.
Just a little curious about the rule to cope with this specific case. If
"crashkernel=size@...set" was passed
but reserve failed, should try again to allocate in high memory,
regardless the specified size@...set,
or just throw a warning and return? Since I noticed the current logic
here on Arm64 is to check if !fixed_base first
before retrying.
Or have I missed anything else?
>> - /* Try again without restricting region to 32bit addressible memory */
>> + /* 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, (unsigned long)dma32_phys_limit),
>> + 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
>>
BR,
Jiahao
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