Hi Jiahao,
On 05/11/23 at 04:51pm, Chen Jiahao wrote:
......
> @@ -1300,14 +1325,34 @@ 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_end = memblock_end_of_DRAM();
> + } else if (ret || !crash_size) {
> + /* Invalid argument value specified */
> return;
> + }
The parsing part looks great, while you didn't mark if it's specified
high reservation, please see later comment why it's needed.
>
> crash_size = PAGE_ALIGN(crash_size);
>
> if (crash_base) {
> + fixed_base = true;
> search_start = crash_base;
> search_end = crash_base + crash_size;
> }
> @@ -1320,17 +1365,31 @@ 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 it's a specified high reservation, you have
search_start = memblock_start_of_DRAM();
search_end = memblock_end_of_DRAM();
Then it attempts to search top down first time here.
> 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;
> + }
> + search_end = memblock_end_of_DRAM();
> +
> + /* Try again above the region of 32bit addressible memory */
> crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE,
> - search_start, search_end);
> + search_start, search_end);
If crashkernel=,high case, the first attempt failed, here it assigns
search_end with memblock_end_of_DRAM(). It's the exactly the same
attempt, why is that needed? Why don't you use a local variable 'high'
to mark the crashkernel=,hig, then judge when deciding how to adjsut the
reservation range.
Do I misunderstand the code?
Thanks
Baoquan
> 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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