Re: [PATCH v12 3/9] x86: kdump: use macro CRASH_ADDR_LOW_MAX in functions reserve_crashkernel[_low]()

Baoquan He
2020-09-18T07:25:44Z

Hi,

On 09/07/20 at 09:47pm, Chen Zhou wrote:
> To make the functions reserve_crashkernel[_low]() as generic,
> replace some hard-coded numbers with macro CRASH_ADDR_LOW_MAX.
>
> Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
> ---
> arch/x86/kernel/setup.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index d7fd90c52dae..71a6a6e7ca5b 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -430,7 +430,7 @@ static int __init reserve_crashkernel_low(void)
> unsigned long total_low_mem;
> int ret;
>
> - total_low_mem = memblock_mem_size(1UL << (32 - PAGE_SHIFT));
> + total_low_mem = memblock_mem_size(CRASH_ADDR_LOW_MAX >> PAGE_SHIFT);

Just note that the replacement has been done in another patch from Mike
Rapoport, partially. He seems to have done reserve_crashkernel_low()
part, there's one left in reserve_crashkernel(), you might want to check
that.

Mike's patch which is from a patchset has been merged into Andrew's next
tree.

commit 6e50f7672ffa362e9bd4bc0c0d2524ed872828c5
Author: Mike Rapoport <rppt@linux.ibm.com>
Date: Wed Aug 26 15:22:32 2020 +1000

x86/setup: simplify reserve_crashkernel()

>
> /* crashkernel=Y,low */
> ret = parse_crashkernel_low(boot_command_line, total_low_mem, &low_size, &base);
> @@ -451,7 +451,7 @@ static int __init reserve_crashkernel_low(void)
> return 0;
> }
>
> - low_base = memblock_find_in_range(CRASH_ALIGN, 1ULL << 32, low_size, CRASH_ALIGN);
> + low_base = memblock_find_in_range(CRASH_ALIGN, CRASH_ADDR_LOW_MAX, low_size, CRASH_ALIGN);
> if (!low_base) {
> pr_err("Cannot reserve %ldMB crashkernel low memory, please try smaller size.\n",
> (unsigned long)(low_size >> 20));
> @@ -504,8 +504,9 @@ static void __init reserve_crashkernel(void)
> if (!crash_base) {
> /*
> * Set CRASH_ADDR_LOW_MAX upper bound for crash memory,
> - * crashkernel=x,high reserves memory over 4G, also allocates
> - * 256M extra low memory for DMA buffers and swiotlb.
> + * crashkernel=x,high reserves memory over CRASH_ADDR_LOW_MAX,
> + * also allocates 256M extra low memory for DMA buffers
> + * and swiotlb.
> * But the extra memory is not required for all machines.
> * So try low memory first and fall back to high memory
> * unless "crashkernel=size[KMG],high" is specified.
> @@ -539,7 +540,7 @@ static void __init reserve_crashkernel(void)
> return;
> }
>
> - if (crash_base >= (1ULL << 32) && reserve_crashkernel_low()) {
> + if (crash_base >= CRASH_ADDR_LOW_MAX && reserve_crashkernel_low()) {
> memblock_free(crash_base, crash_size);
> return;
> }
> --
> 2.20.1
>