The patch titled Subject: crash: fix x86_32 crash memory reserve dead loop bug at high has been added to the -mm mm-nonmm-unstable branch. Its filename is crash-fix-x86_32-crash-memory-reserve-dead-loop-bug-at-high.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/crash-fix-x86_32-crash-memory-reserve-dead-loop-bug-at-high.patch This patch will later appear in the mm-nonmm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Jinjie Ruan <ruanjinjie@xxxxxxxxxx> Subject: crash: fix x86_32 crash memory reserve dead loop bug at high Date: Thu, 18 Jul 2024 11:54:43 +0800 On x86_32 Qemu machine with 1GB memory, the cmdline "crashkernel=512M" will also 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 "low" crash kernel memory reservation for 512M fails, then it go into the "retry" loop and never came out as below (consider CRASH_ADDR_LOW_MAX = CRASH_ADDR_HIGH_MAX = 512M): -> reserve_crashkernel_generic() and high is false -> alloc at [0, 0x20000000] fail -> alloc at [0x20000000, 0x20000000] fail and repeatedly (because CRASH_ADDR_LOW_MAX = CRASH_ADDR_HIGH_MAX). Fix it by skipping meaningless calls of memblock_phys_alloc_range() with `start = end` After this patch, the retry dead loop is avoided and print below info: cannot allocate crashkernel (size:0x20000000) And apply generic crashkernel reservation to 32bit system will be ready. Link: https://lkml.kernel.org/r/20240718035444.2977105-3-ruanjinjie@xxxxxxxxxx Fixes: 9c08a2a139fe ("x86: kdump: use generic interface to simplify crashkernel reservation code") Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx> Signed-off-by: Baoquan He <bhe@xxxxxxxxxx> Tested-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx> Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx> Cc: Andrew Davis <afd@xxxxxx> Cc: Arnd Bergmann <arnd@xxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Chen Jiahao <chenjiahao16@xxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: Dave Young <dyoung@xxxxxxxxxx> Cc: Eric DeVolder <eric.devolder@xxxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Hari Bathini <hbathini@xxxxxxxxxxxxx> Cc: Helge Deller <deller@xxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Javier Martinez Canillas <javierm@xxxxxxxxxx> Cc: Linus Walleij <linus.walleij@xxxxxxxxxx> Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx> Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx> Cc: Rob Herring <robh@xxxxxxxxxx> Cc: Russell King <linux@xxxxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Vivek Goyal <vgoyal@xxxxxxxxxx> Cc: Will Deacon <will@xxxxxxxxxx> Cc: Zhen Lei <thunder.leizhen@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/crash_reserve.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/kernel/crash_reserve.c~crash-fix-x86_32-crash-memory-reserve-dead-loop-bug-at-high +++ a/kernel/crash_reserve.c @@ -413,7 +413,8 @@ retry: search_end = CRASH_ADDR_HIGH_MAX; search_base = CRASH_ADDR_LOW_MAX; crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE; - goto retry; + if (search_base != search_end) + goto retry; } /* _ Patches currently in -mm which might be from ruanjinjie@xxxxxxxxxx are crash-fix-x86_32-crash-memory-reserve-dead-loop-bug.patch crash-fix-x86_32-crash-memory-reserve-dead-loop-bug-at-high.patch arm-use-generic-interface-to-simplify-crashkernel-reservation.patch