Commit a149cf00 authored by Zhen Lei's avatar Zhen Lei Committed by Will Deacon
Browse files

arm64: kdump: Provide default size when crashkernel=Y,low is not specified 



Try to allocate at least 128 MiB low memory automatically for the case
that crashkernel=,high is explicitly specified, while crashkenrel=,low
is omitted. This allows users to focus more on the high memory
requirements of their business rather than the low memory requirements
of the crash kernel booting.

Signed-off-by: default avatarZhen Lei <thunder.leizhen@huawei.com>
Acked-by: default avatarBaoquan He <bhe@redhat.com>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20221116121044.1690-2-thunder.leizhen@huawei.com


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent f0c4d9fc

Documentation/admin-guide/kernel-parameters.txt

+5 −8
Original line number Diff line number Diff line
@@ -851,26 +851,23 @@ 
			available.

			It will be ignored if crashkernel=X is specified.

	crashkernel=size[KMG],low

			[KNL, X86-64] range under 4G. When crashkernel=X,high

			[KNL, X86-64, ARM64] range under 4G. When crashkernel=X,high

			is passed, kernel could allocate physical memory region

			above 4G, that cause second kernel crash on system

			that require some amount of low memory, e.g. swiotlb

			requires at least 64M+32K low memory, also enough extra

			low memory is needed to make sure DMA buffers for 32-bit

			devices won't run out. Kernel would try to allocate

			at least 256M below 4G automatically.

			default	size of memory below 4G automatically. The default

			size is	platform dependent.

			  --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)

			  --> arm64: 128MiB

			This one lets the user specify own low range under 4G

			for second kernel instead.

			0: to disable low allocation.

			It will be ignored when crashkernel=X,high is not used

			or memory reserved is below 4G.



			[KNL, ARM64] range in low memory.

			This one lets the user specify a low range in the

			DMA zone for the crash dump kernel.

			It will be ignored when crashkernel=X,high is not used

			or memory reserved is located in the DMA zones.



	cryptomgr.notests

			[KNL] Disable crypto self-tests

arch/arm64/mm/init.c

+6 −2
Original line number Diff line number Diff line
@@ -96,6 +96,8 @@ phys_addr_t __ro_after_init arm64_dma_phys_limit = PHYS_MASK + 1; 
#define CRASH_ADDR_LOW_MAX		arm64_dma_phys_limit

#define CRASH_ADDR_HIGH_MAX		(PHYS_MASK + 1)



#define DEFAULT_CRASH_KERNEL_LOW_SIZE	(128UL << 20)



static int __init reserve_crashkernel_low(unsigned long long low_size)

{

	unsigned long long low_base;
@@ -147,7 +149,9 @@ static void __init reserve_crashkernel(void) 
		 * is not allowed.

		 */

		ret = parse_crashkernel_low(cmdline, 0, &crash_low_size, &crash_base);

		if (ret && (ret != -ENOENT))

		if (ret == -ENOENT)

			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;

		else if (ret)

			return;



		crash_max = CRASH_ADDR_HIGH_MAX;
@@ -170,7 +174,7 @@ static void __init reserve_crashkernel(void) 
		return;

	}



	if ((crash_base >= CRASH_ADDR_LOW_MAX) &&

	if ((crash_base > CRASH_ADDR_LOW_MAX - crash_low_size) &&

	     crash_low_size && reserve_crashkernel_low(crash_low_size)) {

		memblock_phys_free(crash_base, crash_size);

		return;