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

Baoquan He
2022-03-17T02:36:56Z

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:

> > + * 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
>