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crash: fix x86_32 crash memory reserve dead loop

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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@huawei.com
Fixes: 9c08a2a139 ("x86: kdump: use generic interface to simplify crashkernel reservation code")
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Suggested-by: Baoquan He <bhe@redhat.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Andrew Davis <afd@ti.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen Jiahao <chenjiahao16@huawei.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Eric DeVolder <eric.devolder@oracle.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hari Bathini <hbathini@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Rob Herring (Arm) <robh@kernel.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Will Deacon <will@kernel.org>
Cc: Youling Tang <tangyouling@kylinos.cn>
Cc: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Jinjie Ruan 2024-07-19 17:57:34 +08:00 committed by Andrew Morton
parent 08f14f8a11
commit d2f32f2319
1 changed files with 2 additions and 1 deletions
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3
kernel/crash_reserve.c
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@ -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;
}
pr_warn("cannot allocate crashkernel (size:0x%llx)\n",