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Subject: Re: [PATCH v2 7/8] arm64: kdump: use generic interface to simplify
 crashkernel reservation
To:     Baoquan He <bhe@redhat.com>, linux-kernel@vger.kernel.org
Cc:     akpm@linux-foundation.org, catalin.marinas@arm.com,
        thunder.leizhen@huawei.com, dyoung@redhat.com, prudo@redhat.com,
        samuel.holland@sifive.com, kexec@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, x86@kernel.org
References: <20230829121610.138107-1-bhe@redhat.com>
 <20230829121610.138107-8-bhe@redhat.com>
From:   "Leizhen (ThunderTown)" <thunder.leizhen@huaweicloud.com>
Message-ID: <54bb7826-ef3b-0ab2-68b3-e73c7e0d6b35@huaweicloud.com>
Date:   Thu, 31 Aug 2023 11:51:06 +0800
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On 2023/8/29 20:16, Baoquan He wrote:
> With the help of newly changed function parse_crashkernel() and
> generic reserve_crashkernel_generic(), crashkernel reservation can be
> simplified by steps:
> 
> 1) Add a new header file <asm/crash_core.h>, and define CRASH_ALIGN,
>    CRASH_ADDR_LOW_MAX, CRASH_ADDR_HIGH_MAX and
>    DEFAULT_CRASH_KERNEL_LOW_SIZE in <asm/crash_core.h>;
> 
> 2) Add arch_reserve_crashkernel() to call parse_crashkernel() and
>    reserve_crashkernel_generic();
> 
> 3) Add ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION Kconfig in
>    arch/arm64/Kconfig.
> 
> The old reserve_crashkernel_low() and reserve_crashkernel() can be
> removed.

Reviewed-by: Zhen Lei <thunder.leizhen@huawei.com>

> 
> Signed-off-by: Baoquan He <bhe@redhat.com>
> ---
>  arch/arm64/Kconfig                  |   3 +
>  arch/arm64/include/asm/crash_core.h |  10 ++
>  arch/arm64/mm/init.c                | 140 ++--------------------------
>  3 files changed, 21 insertions(+), 132 deletions(-)
>  create mode 100644 arch/arm64/include/asm/crash_core.h
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 29db061db9bb..07fb8c71339d 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1481,6 +1481,9 @@ config KEXEC_FILE
>  	  for kernel and initramfs as opposed to list of segments as
>  	  accepted by previous system call.
>  
> +config ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
> +	def_bool CRASH_CORE
> +
>  config KEXEC_SIG
>  	bool "Verify kernel signature during kexec_file_load() syscall"
>  	depends on KEXEC_FILE
> diff --git a/arch/arm64/include/asm/crash_core.h b/arch/arm64/include/asm/crash_core.h
> new file mode 100644
> index 000000000000..9f5c8d339f44
> --- /dev/null
> +++ b/arch/arm64/include/asm/crash_core.h
> @@ -0,0 +1,10 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +#ifndef _ARM64_CRASH_CORE_H
> +#define _ARM64_CRASH_CORE_H
> +
> +/* Current arm64 boot protocol requires 2MB alignment */
> +#define CRASH_ALIGN                     SZ_2M
> +
> +#define CRASH_ADDR_LOW_MAX              arm64_dma_phys_limit
> +#define CRASH_ADDR_HIGH_MAX             (PHYS_MASK + 1)
> +#endif
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 4ad637508b75..48ab23531bb6 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -64,15 +64,6 @@ EXPORT_SYMBOL(memstart_addr);
>   */
>  phys_addr_t __ro_after_init arm64_dma_phys_limit;
>  
> -/* Current arm64 boot protocol requires 2MB alignment */
> -#define CRASH_ALIGN			SZ_2M
> -
> -#define CRASH_ADDR_LOW_MAX		arm64_dma_phys_limit
> -#define CRASH_ADDR_HIGH_MAX		(PHYS_MASK + 1)
> -#define CRASH_HIGH_SEARCH_BASE		SZ_4G
> -
> -#define DEFAULT_CRASH_KERNEL_LOW_SIZE	(128UL << 20)
> -
>  /*
>   * To make optimal use of block mappings when laying out the linear
>   * mapping, round down the base of physical memory to a size that can
> @@ -100,140 +91,25 @@ phys_addr_t __ro_after_init arm64_dma_phys_limit;
>  #define ARM64_MEMSTART_ALIGN	(1UL << ARM64_MEMSTART_SHIFT)
>  #endif
>  
> -static int __init reserve_crashkernel_low(unsigned long long low_size)
> -{
> -	unsigned long long low_base;
> -
> -	low_base = memblock_phys_alloc_range(low_size, CRASH_ALIGN, 0, CRASH_ADDR_LOW_MAX);
> -	if (!low_base) {
> -		pr_err("cannot allocate crashkernel low memory (size:0x%llx).\n", low_size);
> -		return -ENOMEM;
> -	}
> -
> -	pr_info("crashkernel low memory reserved: 0x%08llx - 0x%08llx (%lld MB)\n",
> -		low_base, low_base + low_size, low_size >> 20);
> -
> -	crashk_low_res.start = low_base;
> -	crashk_low_res.end   = low_base + low_size - 1;
> -	insert_resource(&iomem_resource, &crashk_low_res);
> -
> -	return 0;
> -}
> -
> -/*
> - * reserve_crashkernel() - reserves memory for crash kernel
> - *
> - * This function reserves memory area given in "crashkernel=" kernel command
> - * line parameter. The memory reserved is used by dump capture kernel when
> - * primary kernel is crashing.
> - */
> -static void __init reserve_crashkernel(void)
> +static void __init arch_reserve_crashkernel(void)
>  {
> -	unsigned long long crash_low_size = 0, search_base = 0;
> -	unsigned long long crash_max = CRASH_ADDR_LOW_MAX;
> +	unsigned long long low_size = 0;
>  	unsigned long long crash_base, crash_size;
>  	char *cmdline = boot_command_line;
> -	bool fixed_base = false;
>  	bool high = false;
>  	int ret;
>  
>  	if (!IS_ENABLED(CONFIG_KEXEC_CORE))
>  		return;
>  
> -	/* crashkernel=X[@offset] */
>  	ret = parse_crashkernel(cmdline, memblock_phys_mem_size(),
> -				&crash_size, &crash_base, NULL, NULL);
> -	if (ret == -ENOENT) {
> -		ret = parse_crashkernel_high(cmdline, 0, &crash_size, &crash_base);
> -		if (ret || !crash_size)
> -			return;
> -
> -		/*
> -		 * crashkernel=Y,low can be specified or not, but invalid value
> -		 * is not allowed.
> -		 */
> -		ret = parse_crashkernel_low(cmdline, 0, &crash_low_size, &crash_base);
> -		if (ret == -ENOENT)
> -			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
> -		else if (ret)
> -			return;
> -
> -		search_base = CRASH_HIGH_SEARCH_BASE;
> -		crash_max = CRASH_ADDR_HIGH_MAX;
> -		high = true;
> -	} else if (ret || !crash_size) {
> -		/* The specified value is invalid */
> +				&crash_size, &crash_base,
> +				&low_size, &high);
> +	if (ret)
>  		return;
> -	}
> -
> -	crash_size = PAGE_ALIGN(crash_size);
> -
> -	/* User specifies base address explicitly. */
> -	if (crash_base) {
> -		fixed_base = true;
> -		search_base = crash_base;
> -		crash_max = crash_base + crash_size;
> -	}
> -
> -retry:
> -	crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN,
> -					       search_base, crash_max);
> -	if (!crash_base) {
> -		/*
> -		 * For crashkernel=size[KMG]@offset[KMG], print out failure
> -		 * message if can't reserve the specified region.
> -		 */
> -		if (fixed_base) {
> -			pr_warn("crashkernel reservation failed - memory is in use.\n");
> -			return;
> -		}
> -
> -		/*
> -		 * For crashkernel=size[KMG], if the first attempt was for
> -		 * low memory, fall back to high memory, the minimum required
> -		 * low memory will be reserved later.
> -		 */
> -		if (!high && crash_max == CRASH_ADDR_LOW_MAX) {
> -			crash_max = CRASH_ADDR_HIGH_MAX;
> -			search_base = CRASH_ADDR_LOW_MAX;
> -			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
> -			goto retry;
> -		}
> -
> -		/*
> -		 * For crashkernel=size[KMG],high, if the first attempt was
> -		 * for high memory, fall back to low memory.
> -		 */
> -		if (high && crash_max == CRASH_ADDR_HIGH_MAX) {
> -			crash_max = CRASH_ADDR_LOW_MAX;
> -			search_base = 0;
> -			goto retry;
> -		}
> -		pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
> -			crash_size);
> -		return;
> -	}
> -
> -	if ((crash_base >= CRASH_ADDR_LOW_MAX) && crash_low_size &&
> -	     reserve_crashkernel_low(crash_low_size)) {
> -		memblock_phys_free(crash_base, crash_size);
> -		return;
> -	}
> -
> -	pr_info("crashkernel reserved: 0x%016llx - 0x%016llx (%lld MB)\n",
> -		crash_base, crash_base + crash_size, crash_size >> 20);
> -
> -	/*
> -	 * The crashkernel memory will be removed from the kernel linear
> -	 * map. Inform kmemleak so that it won't try to access it.
> -	 */
> -	kmemleak_ignore_phys(crash_base);
> -	if (crashk_low_res.end)
> -		kmemleak_ignore_phys(crashk_low_res.start);
>  
> -	crashk_res.start = crash_base;
> -	crashk_res.end = crash_base + crash_size - 1;
> -	insert_resource(&iomem_resource, &crashk_res);
> +	reserve_crashkernel_generic(cmdline, crash_size, crash_base,
> +				    low_size, high);
>  }
>  
>  /*
> @@ -481,7 +357,7 @@ void __init bootmem_init(void)
>  	 * request_standard_resources() depends on crashkernel's memory being
>  	 * reserved, so do it here.
>  	 */
> -	reserve_crashkernel();
> +	arch_reserve_crashkernel();
>  
>  	memblock_dump_all();
>  }
> 

-- 
Regards,
  Zhen Lei