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/crash-fix-x86_32-memory-reserve-dead-loop-retry-bug.patch
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@xxxxxxxxxx>
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@xxxxxxxxxx
Fixes: 9c08a2a139fe ("x86: kdump: use generic interface to simplify crashkernel reservation code")
Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
Cc: Baoquan He <bhe@xxxxxxxxxx>
Cc: Dave Young <dyoung@xxxxxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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@xxxxxxxxxx are
crash-fix-x86_32-memory-reserve-dead-loop-retry-bug.patch
