[PATCH v3 1/3] crash: Fix x86_32 crash memory reserve dead loop bug

[Jinjie Ruan]

On 2024/7/18 19:10, Baoquan He wrote:
> On 07/18/24 at 11:54am, Jinjie Ruan wrote:
>> 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 prevent crashkernel=,high from being parsed successfully on 32bit
>> system with a architecture-defined macro.
>>
>> After this patch, the 'crashkernel=,high' for 32bit system can't succeed,
>> and it has no chance to call reserve_crashkernel_generic(), therefore this
>> issue on x86_32 is solved.
>>
>> Fixes: 9c08a2a139fe ("x86: kdump: use generic interface to simplify crashkernel reservation code")
>> Signed-off-by: Jinjie Ruan <ruanjinjie at huawei.com>
>> Signed-off-by: Baoquan He <bhe at redhat.com>
> 
> Just adding my Suggested-by is fine. If multiple people cooperate on one
> patch, the Co-developed-by tag is needed. As a maintainer, I prefer to
> have the Suggested-by tag in this case.

Hi, Baoquan, I wonder if riscv32 have a similar problem, but I'm not sure.

> 
>> Tested-by: Jinjie Ruan <ruanjinjie at huawei.com>
> 
> You can't add Tested-by tag for your own patch. When you post patch,
> testing it is your obligation.
> 
> Other than these tag adding concerns, this patch looks good to me. You
> can post v4 to update and add my:
> 
> Acked-by: Baoquan He <bhe at redhat.com>
> 
>> ---
>> v3:
>> - Fix it as Baoquan suggested.
>> - Update the commit message.
>> v2:
>> - Peel off the other two patches.
>> - Update the commit message and fix tag.
>> ---
>>  arch/arm64/include/asm/crash_reserve.h | 2 ++
>>  arch/riscv/include/asm/crash_reserve.h | 2 ++
>>  arch/x86/include/asm/crash_reserve.h   | 1 +
>>  kernel/crash_reserve.c                 | 2 +-
>>  4 files changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/include/asm/crash_reserve.h b/arch/arm64/include/asm/crash_reserve.h
>> index 4afe027a4e7b..bf362c1a612f 100644
>> --- a/arch/arm64/include/asm/crash_reserve.h
>> +++ b/arch/arm64/include/asm/crash_reserve.h
>> @@ -7,4 +7,6 @@
>>  
>>  #define CRASH_ADDR_LOW_MAX              arm64_dma_phys_limit
>>  #define CRASH_ADDR_HIGH_MAX             (PHYS_MASK + 1)
>> +
>> +#define HAVE_ARCH_CRASHKERNEL_RESERVATION_HIGH
>>  #endif
>> diff --git a/arch/riscv/include/asm/crash_reserve.h b/arch/riscv/include/asm/crash_reserve.h
>> index 013962e63587..8d7a8fc1d459 100644
>> --- a/arch/riscv/include/asm/crash_reserve.h
>> +++ b/arch/riscv/include/asm/crash_reserve.h
>> @@ -7,5 +7,7 @@
>>  #define CRASH_ADDR_LOW_MAX		dma32_phys_limit
>>  #define CRASH_ADDR_HIGH_MAX		memblock_end_of_DRAM()
>>  
>> +#define HAVE_ARCH_CRASHKERNEL_RESERVATION_HIGH
>> +
>>  extern phys_addr_t memblock_end_of_DRAM(void);
>>  #endif
>> diff --git a/arch/x86/include/asm/crash_reserve.h b/arch/x86/include/asm/crash_reserve.h
>> index 7835b2cdff04..24c2327f9a16 100644
>> --- a/arch/x86/include/asm/crash_reserve.h
>> +++ b/arch/x86/include/asm/crash_reserve.h
>> @@ -26,6 +26,7 @@ extern unsigned long swiotlb_size_or_default(void);
>>  #else
>>  # define CRASH_ADDR_LOW_MAX     SZ_4G
>>  # define CRASH_ADDR_HIGH_MAX    SZ_64T
>> +#define HAVE_ARCH_CRASHKERNEL_RESERVATION_HIGH
>>  #endif
>>  
>>  # define DEFAULT_CRASH_KERNEL_LOW_SIZE crash_low_size_default()
>> diff --git a/kernel/crash_reserve.c b/kernel/crash_reserve.c
>> index 5b2722a93a48..c5213f123e19 100644
>> --- a/kernel/crash_reserve.c
>> +++ b/kernel/crash_reserve.c
>> @@ -306,7 +306,7 @@ int __init parse_crashkernel(char *cmdline,
>>  	/* crashkernel=X[@offset] */
>>  	ret = __parse_crashkernel(cmdline, system_ram, crash_size,
>>  				crash_base, NULL);
>> -#ifdef CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
>> +#ifdef HAVE_ARCH_CRASHKERNEL_RESERVATION_HIGH
>>  	/*
>>  	 * If non-NULL 'high' passed in and no normal crashkernel
>>  	 * setting detected, try parsing crashkernel=,high|low.
>> -- 
>> 2.34.1
>>
> 
>