The patch titled Subject: crash: fix x86_32 memory reserve dead loop retry bug has been added to the -mm mm-hotfixes-unstable branch. Its filename is crash-fix-x86_32-memory-reserve-dead-loop-retry-bug.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Jinjie Ruan ruanjinjie@huawei.com Subject: crash: fix x86_32 memory reserve dead loop retry bug Date: Thu, 11 Jul 2024 15:31:18 +0800

On x86_32 Qemu machine with 1GB memory, the cmdline "crashkernel=1G,high" will cause system stall as below:

ACPI: Reserving FACP table memory at [mem 0x3ffe18b8-0x3ffe192b] ACPI: Reserving DSDT table memory at [mem 0x3ffe0040-0x3ffe18b7] ACPI: Reserving FACS table memory at [mem 0x3ffe0000-0x3ffe003f] ACPI: Reserving APIC table memory at [mem 0x3ffe192c-0x3ffe19bb] ACPI: Reserving HPET table memory at [mem 0x3ffe19bc-0x3ffe19f3] ACPI: Reserving WAET table memory at [mem 0x3ffe19f4-0x3ffe1a1b] 143MB HIGHMEM available. 879MB LOWMEM available. mapped low ram: 0 - 36ffe000 low ram: 0 - 36ffe000 (stall here)

The reason is that the CRASH_ADDR_LOW_MAX is equal to CRASH_ADDR_HIGH_MAX on x86_32, the first high crash kernel memory reservation will fail, then go into the "retry" loop and never came out as below.

-> reserve_crashkernel_generic() and high is true -> alloc at [CRASH_ADDR_LOW_MAX, CRASH_ADDR_HIGH_MAX] fail -> alloc at [0, CRASH_ADDR_LOW_MAX] fail and repeatedly (because CRASH_ADDR_LOW_MAX = CRASH_ADDR_HIGH_MAX).

Fix it by changing the out check condition.

After this patch, it prints: cannot allocate crashkernel (size:0x40000000)

Link: https://lkml.kernel.org/r/20240711073118.1289866-1-ruanjinjie@huawei.com Fixes: 9c08a2a139fe ("x86: kdump: use generic interface to simplify crashkernel reservation code") Signed-off-by: Jinjie Ruan ruanjinjie@huawei.com Cc: Baoquan He bhe@redhat.com Cc: Dave Young dyoung@redhat.com Cc: Vivek Goyal vgoyal@redhat.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

kernel/crash_reserve.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/crash_reserve.c~crash-fix-x86_32-memory-reserve-dead-loop-retry-bug +++ a/kernel/crash_reserve.c @@ -421,7 +421,7 @@ retry: * For crashkernel=size[KMG],high, if the first attempt was * for high memory, fall back to low memory. */ - if (high && search_end == CRASH_ADDR_HIGH_MAX) { + if (high && search_base == CRASH_ADDR_LOW_MAX) { search_end = CRASH_ADDR_LOW_MAX; search_base = 0; goto retry; _

Patches currently in -mm which might be from ruanjinjie@huawei.com are

crash-fix-x86_32-memory-reserve-dead-loop-retry-bug.patch