The patch titled
Subject: crash: fix x86_32 crash memory reserve dead loop
has been added to the -mm mm-nonmm-unstable branch. Its filename is
crash-fix-x86_32-crash-memory-reserve-dead-loop.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.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
Subject: crash: fix x86_32 crash memory reserve dead loop
Date: Fri, 19 Jul 2024 17:57:34 +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 we print the below info:
cannot allocate crashkernel (size:0x20000000)
And we will be ready to apply the generic crashkernel reservation to
32bit systems.
Link: https://lkml.kernel.org/r/20240719095735.1912878-3-ruanjinjie@xxxxxxxxxx
Fixes: 9c08a2a139fe ("x86: kdump: use generic interface to simplify crashkernel reservation code")
Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
Suggested-by: Baoquan He <bhe@xxxxxxxxxx>
Acked-by: Baoquan He <bhe@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: Huacai Chen <chenhuacai@xxxxxxxxxx>
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 (Arm) <robh@xxxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
Cc: WANG Xuerui <kernel@xxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Youling Tang <tangyouling@xxxxxxxxxx>
Cc: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
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
+++ 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.patch
arm-use-generic-interface-to-simplify-crashkernel-reservation.patch
