Re: [PATCH -next 1/2] riscv: kdump: Implement crashkernel=X,[high,low]

Simon Horman
2023-03-20T14:37:11Z

On Tue, Mar 21, 2023 at 04:42:43AM +0800, 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].
>
> We 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>

Some minor nits, but I don't think there is any need to respin for them.

Reviewed-by: Simon Horman <horms@kernel.org>

...

> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 478d6763a01a..5def2174b243 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c

...

> @@ -1201,16 +1242,25 @@ 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));

nit: While here, you could drop the space before 'ma32_phys_limit'.
Or perhaps use min_t, which seems appropriate here.

> if (crash_base == 0) {
> /* Try again without restricting region to 32bit addressible memory */
> 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;
> + }
> +
> + if ((crash_base > dma32_phys_limit - crash_low_size) &&
> + crash_low_size && reserve_crashkernel_low(crash_low_size)) {

nit: The line above should be aligned one character to the left
(remove one space in the indent).

> + memblock_phys_free(crash_base, crash_size);
> + return;
> }
>
> pr_info("crashkernel: reserved 0x%016llx - 0x%016llx (%lld MB)\n",

...