Re: [PATCH v21 3/5] arm64: kdump: reimplement crashkernel=X

Baoquan He
2022-03-17T06:13:28Z

On 03/17/22 at 11:19am, Leizhen (ThunderTown) wrote:
>
>
> On 2022/3/17 10:36, Baoquan He wrote:
> > On 03/16/22 at 09:11pm, Leizhen (ThunderTown) wrote:
> >>
> >>
> >> On 2022/3/16 20:11, Baoquan He wrote:
> >>> On 02/27/22 at 11:07am, Zhen Lei wrote:
> > ......
> >
> >>> Hi leizhen,
> >>>
> >>> I made change on reserve_crashkenrel(), inline comment may be slow.
> >>> Please check and consider if they can be taken.
> >>
> >> That's great. Thank you very much.
> >>
> >>>
> >>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> >>> index 30ae6638ff54..f96351da1e3e 100644
> >>> --- a/arch/arm64/mm/init.c
> >>> +++ b/arch/arm64/mm/init.c
> >>> @@ -109,38 +109,43 @@ static int __init reserve_crashkernel_low(unsigned long long low_size)
> >>> * This function reserves memory area given in "crashkernel=" kernel command
> >>> * line parameter. The memory reserved is used by dump capture kernel when
> >>> * primary kernel is crashing.
> >>> + *
> >>> + * NOTE: Reservation of crashkernel,low is special since its existence
> >>> + * is not independent, need rely on the existence of crashkernel,high.
> >>> + * Hence there are different cases for crashkernel,low reservation:
> >
> > Considering to update the 3rd line as below:
> >
> > * NOTE: Reservation of crashkernel,low is special since its existence
> > * is not independent, need rely on the existence of crashkernel,high.
> > * Here, four cases of crashkernel,low reservation are summarized:
>
> OK. How about change "crashkernel,low" to "crashkernel low memory"?
> "crashkernel=Y,low", "crashkernel=,low" and "crashkernel,low" are very similar,
> may dazzle the reader.

Fine by me. 'crashkernel low memory' is formal, just make sentence a
little longer. Please take what you think fitter.

>
> >
> >>> + * 1) crashkernel=Y,low is specified explicitly, crashkernel,low takes Y;
> >>> + * 2) crashkernel=,low is not given, while crashkernel=,high is specified,
> >>> + * take the default crashkernel,low value;
> >>> + * 3) crashkernel=X is specified, while fallback to get a memory region
> >>> + * in high memory, take the default crashkernel,low value;
> >>> + * 4) crashkernel='invalid value',low is specified, failed the whole
> >>> + * crashkernel reservation and bail out.
> >>> */
> >>> static void __init reserve_crashkernel(void)
> >>> {
> >>> unsigned long long crash_base, crash_size;
> >>> unsigned long long crash_low_size;
> >>> unsigned long long crash_max = CRASH_ADDR_LOW_MAX;
> >>> - int ret;
> >>> bool fixed_base, high = false;
> >>> char *cmdline = boot_command_line;
> >>> + int ret;
> >>>
> >>> /* crashkernel=X[@offset] */
> >>> ret = parse_crashkernel(cmdline, memblock_phys_mem_size(),
> >>> &crash_size, &crash_base);
> >>> if (ret || !crash_size) {
> >>> - /* crashkernel=X,high */
> >>> ret = parse_crashkernel_high(cmdline, 0, &crash_size, &crash_base);
> >>> if (ret || !crash_size)
> >>> return;
> >>>
> >>> - /* crashkernel=Y,low */
> >>> ret = parse_crashkernel_low(cmdline, 0, &crash_low_size, &crash_base);
> >>> if (ret == -ENOENT)
> >>> - /*
> >>> - * crashkernel=Y,low is not specified explicitly, use
> >>> - * default size automatically.
> >>> - */
> >>> + /* case #2 of crashkernel,low reservation */
> >>> crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
> >>> else if (ret)
> >>> - /* crashkernel=Y,low is specified but Y is invalid */
> >>> + /* case #4 of crashkernel,low reservation */
> >>> return;
> >>>
> >>> - /* Mark crashkernel=X,high is specified */
> >>> high = true;
> >>> crash_max = CRASH_ADDR_HIGH_MAX;
> >>> }
> >>> @@ -148,7 +153,6 @@ static void __init reserve_crashkernel(void)
> >>> fixed_base = !!crash_base;
> >>> crash_size = PAGE_ALIGN(crash_size);
> >>>
> >>> - /* User specifies base address explicitly. */
> >>> if (fixed_base)
> >>> crash_max = crash_base + crash_size;
> >>>
> >>> @@ -172,11 +176,7 @@ static void __init reserve_crashkernel(void)
> >>> }
> >>>
> >>> if (crash_base >= SZ_4G) {
> >>> - /*
> >>> - * For case crashkernel=X, low memory is not enough and fall
> >>> - * back to reserve specified size of memory above 4G, try to
> >>> - * allocate minimum required memory below 4G again.
> >>> - */
> >>> + /* case #3 of crashkernel,low reservation */
> >>> if (!high)
> >>> crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
> >>>
> >>>
> >>>>
> >>>> - /* Current arm64 boot protocol requires 2MB alignment */
> >>>> - crash_base = memblock_phys_alloc_range(crash_size, SZ_2M,
> >>>> +retry:
> >>>> + crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN,
> >>>> crash_base, crash_max);
> >>>> if (!crash_base) {
> >>>> + /*
> >>>> + * Attempt to fully allocate low memory failed, fall back
> >>>> + * to high memory, the minimum required low memory will be
> >>>> + * reserved later.
> >>>> + */
> >>>> + if (!fixed_base && (crash_max == CRASH_ADDR_LOW_MAX)) {
> >>>> + crash_max = CRASH_ADDR_HIGH_MAX;
> >>>> + goto retry;
> >>>> + }
> >>>> +
> >>>> pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
> >>>> crash_size);
> >>>> return;
> >>>> }
> >>>>
> >>>> + if (crash_base >= SZ_4G) {
> >>>> + /*
> >>>> + * For case crashkernel=X, low memory is not enough and fall
> >>>> + * back to reserve specified size of memory above 4G, try to
> >>>> + * allocate minimum required memory below 4G again.
> >>>> + */
> >>>> + if (!high)
> >>>> + crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
> >>>> +
> >>>> + if (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",
> >>>> crash_base, crash_base + crash_size, crash_size >> 20);
> >>>>
> >>>> @@ -107,6 +194,9 @@ static void __init reserve_crashkernel(void)
> >>>> * map. Inform kmemleak so that it won't try to access it.
> >>>> */
> >>>> kmemleak_ignore_phys(crash_base);
> >>>> + if (crashk_low_res.end)
> >>>> + kmemleak_ignore_phys(crashk_low_res.start);
> >>>> +
> >>>> crashk_res.start = crash_base;
> >>>> crashk_res.end = crash_base + crash_size - 1;
> >>>> insert_resource(&iomem_resource, &crashk_res);
> >>>> --
> >>>> 2.25.1
> >>>>
> >>>
> >>> .
> >>>
> >>
> >> --
> >> Regards,
> >> Zhen Lei
> >>
> >
> > .
> >
>
> --
> Regards,
> Zhen Lei
>