Subject: Re: [PATCH v13 4/8] x86: kdump: move reserve_crashkernel[_low]() into crash_core.c

From: Mike Rapoport <[email-masked]>
Date: Thu, 12 Nov 2020 10:11:52 +0200

On Sat, Oct 31, 2020 at 03:44:33PM +0800, Chen Zhou wrote:
> Make the functions reserve_crashkernel[_low]() as generic.
> Arm64 will use these to reimplement crashkernel=X.
> 
> Signed-off-by: Chen Zhou <[email-masked]>
> Tested-by: John Donnelly <[email-masked]>
> ---
>  arch/x86/include/asm/kexec.h |  25 ++++++
>  arch/x86/kernel/setup.c      | 151 +-------------------------------
>  include/linux/crash_core.h   |   4 +
>  include/linux/kexec.h        |   2 -
>  kernel/crash_core.c          | 164 +++++++++++++++++++++++++++++++++++
>  kernel/kexec_core.c          |  17 ----
>  6 files changed, 195 insertions(+), 168 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
> index 8cf9d3fd31c7..34afa7b645f9 100644
> --- a/arch/x86/include/asm/kexec.h
> +++ b/arch/x86/include/asm/kexec.h
> @@ -21,6 +21,27 @@
>  /* 2M alignment for crash kernel regions */
>  #define CRASH_ALIGN		SZ_16M
>  
> +/*
> + * Keep the crash kernel below this limit.
> + *
> + * Earlier 32-bits kernels would limit the kernel to the low 512 MB range
> + * due to mapping restrictions.
> + *
> + * 64-bit kdump kernels need to be restricted to be under 64 TB, which is
> + * the upper limit of system RAM in 4-level paging mode. Since the kdump
> + * jump could be from 5-level paging to 4-level paging, the jump will fail if
> + * the kernel is put above 64 TB, and during the 1st kernel bootup there's
> + * no good way to detect the paging mode of the target kernel which will be
> + * loaded for dumping.
> + */
> +#ifdef CONFIG_X86_32
> +# define CRASH_ADDR_LOW_MAX	SZ_512M
> +# define CRASH_ADDR_HIGH_MAX	SZ_512M
> +#else
> +# define CRASH_ADDR_LOW_MAX	SZ_4G
> +# define CRASH_ADDR_HIGH_MAX	SZ_64T
> +#endif
> +
>  #ifndef __ASSEMBLY__
>  
>  #include <linux/string.h>
> @@ -200,6 +221,10 @@ typedef void crash_vmclear_fn(void);
>  extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss;
>  extern void kdump_nmi_shootdown_cpus(void);
>  
> +#ifdef CONFIG_KEXEC_CORE
> +extern void __init reserve_crashkernel(void);
> +#endif
> +
>  #endif /* __ASSEMBLY__ */
>  
>  #endif /* _ASM_X86_KEXEC_H */
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 1289f079ad5f..00b3840d30f9 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -25,8 +25,6 @@
>  
>  #include <uapi/linux/mount.h>
>  
> -#include <xen/xen.h>
> -
>  #include <asm/apic.h>
>  #include <asm/numa.h>
>  #include <asm/bios_ebda.h>
> @@ -38,6 +36,7 @@
>  #include <asm/io_apic.h>
>  #include <asm/kasan.h>
>  #include <asm/kaslr.h>
> +#include <asm/kexec.h>
>  #include <asm/mce.h>
>  #include <asm/mtrr.h>
>  #include <asm/realmode.h>
> @@ -389,153 +388,7 @@ static void __init memblock_x86_reserve_range_setup_data(void)
>  	}
>  }
>  
> -/*
> - * --------- Crashkernel reservation ------------------------------
> - */
> -
> -#ifdef CONFIG_KEXEC_CORE
> -
> -/*
> - * Keep the crash kernel below this limit.
> - *
> - * Earlier 32-bits kernels would limit the kernel to the low 512 MB range
> - * due to mapping restrictions.
> - *
> - * 64-bit kdump kernels need to be restricted to be under 64 TB, which is
> - * the upper limit of system RAM in 4-level paging mode. Since the kdump
> - * jump could be from 5-level paging to 4-level paging, the jump will fail if
> - * the kernel is put above 64 TB, and during the 1st kernel bootup there's
> - * no good way to detect the paging mode of the target kernel which will be
> - * loaded for dumping.
> - */
> -#ifdef CONFIG_X86_32
> -# define CRASH_ADDR_LOW_MAX	SZ_512M
> -# define CRASH_ADDR_HIGH_MAX	SZ_512M
> -#else
> -# define CRASH_ADDR_LOW_MAX	SZ_4G
> -# define CRASH_ADDR_HIGH_MAX	SZ_64T
> -#endif
> -
> -static int __init reserve_crashkernel_low(void)
> -{
> -#ifdef CONFIG_X86_64
> -	unsigned long long base, low_base = 0, low_size = 0;
> -	unsigned long low_mem_limit;
> -	int ret;
> -
> -	low_mem_limit = min(memblock_phys_mem_size(), CRASH_ADDR_LOW_MAX);
> -
> -	/* crashkernel=Y,low */
> -	ret = parse_crashkernel_low(boot_command_line, low_mem_limit, &low_size, &base);
> -	if (ret) {
> -		/*
> -		 * two parts from kernel/dma/swiotlb.c:
> -		 * -swiotlb size: user-specified with swiotlb= or default.
> -		 *
> -		 * -swiotlb overflow buffer: now hardcoded to 32k. We round it
> -		 * to 8M for other buffers that may need to stay low too. Also
> -		 * make sure we allocate enough extra low memory so that we
> -		 * don't run out of DMA buffers for 32-bit devices.
> -		 */
> -		low_size = max(swiotlb_size_or_default() + (8UL << 20), 256UL << 20);
> -	} else {
> -		/* passed with crashkernel=0,low ? */
> -		if (!low_size)
> -			return 0;
> -	}
> -
> -	low_base = memblock_phys_alloc_range(low_size, CRASH_ALIGN, CRASH_ALIGN, CRASH_ADDR_LOW_MAX);
> -	if (!low_base) {
> -		pr_err("Cannot reserve %ldMB crashkernel low memory, please try smaller size.\n",
> -		       (unsigned long)(low_size >> 20));
> -		return -ENOMEM;
> -	}
> -
> -	pr_info("Reserving %ldMB of low memory at %ldMB for crashkernel (low RAM limit: %ldMB)\n",
> -		(unsigned long)(low_size >> 20),
> -		(unsigned long)(low_base >> 20),
> -		(unsigned long)(low_mem_limit >> 20));
> -
> -	crashk_low_res.start = low_base;
> -	crashk_low_res.end   = low_base + low_size - 1;
> -	insert_resource(&iomem_resource, &crashk_low_res);
> -#endif
> -	return 0;
> -}
> -
> -static void __init reserve_crashkernel(void)
> -{
> -	unsigned long long crash_size, crash_base, total_mem;
> -	bool high = false;
> -	int ret;
> -
> -	total_mem = memblock_phys_mem_size();
> -
> -	/* crashkernel=XM */
> -	ret = parse_crashkernel(boot_command_line, total_mem, &crash_size, &crash_base);
> -	if (ret != 0 || crash_size <= 0) {
> -		/* crashkernel=X,high */
> -		ret = parse_crashkernel_high(boot_command_line, total_mem,
> -					     &crash_size, &crash_base);
> -		if (ret != 0 || crash_size <= 0)
> -			return;
> -		high = true;
> -	}
> -
> -	if (xen_pv_domain()) {
> -		pr_info("Ignoring crashkernel for a Xen PV domain\n");
> -		return;
> -	}

This is relevant only to x86, maybe we could move this check to
setup_arch before calling reserve_crashkernel() to keep it in x86?

> -
> -	/* 0 means: find the address automatically */
> -	if (!crash_base) {
> -		/*
> -		 * Set CRASH_ADDR_LOW_MAX upper bound for crash memory,
> -		 * crashkernel=x,high reserves memory over CRASH_ADDR_LOW_MAX,
> -		 * also allocates 256M extra low memory for DMA buffers
> -		 * and swiotlb.
> -		 * But the extra memory is not required for all machines.
> -		 * So try low memory first and fall back to high memory
> -		 * unless "crashkernel=size[KMG],high" is specified.
> -		 */
> -		if (!high)
> -			crash_base = memblock_phys_alloc_range(crash_size,
> -						CRASH_ALIGN, CRASH_ALIGN,
> -						CRASH_ADDR_LOW_MAX);
> -		if (!crash_base)
> -			crash_base = memblock_phys_alloc_range(crash_size,
> -						CRASH_ALIGN, CRASH_ALIGN,
> -						CRASH_ADDR_HIGH_MAX);
> -		if (!crash_base) {
> -			pr_info("crashkernel reservation failed - No suitable area found.\n");
> -			return;
> -		}
> -	} else {
> -		unsigned long long start;
> -
> -		start = memblock_phys_alloc_range(crash_size, CRASH_ALIGN, crash_base,
> -						  crash_base + crash_size);
> -		if (start != crash_base) {
> -			pr_info("crashkernel reservation failed - memory is in use.\n");
> -			return;
> -		}
> -	}
> -
> -	if (crash_base >= CRASH_ADDR_LOW_MAX && reserve_crashkernel_low()) {
> -		memblock_free(crash_base, crash_size);
> -		return;
> -	}
> -
> -	pr_info("Reserving %ldMB of memory at %ldMB for crashkernel (System RAM: %ldMB)\n",
> -		(unsigned long)(crash_size >> 20),
> -		(unsigned long)(crash_base >> 20),
> -		(unsigned long)(total_mem >> 20));
> -
> -	crashk_res.start = crash_base;
> -	crashk_res.end   = crash_base + crash_size - 1;
> -	insert_resource(&iomem_resource, &crashk_res);
> -}
> -#else
> +#ifndef CONFIG_KEXEC_CORE
>  static void __init reserve_crashkernel(void)
>  {
>  }
> diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
> index 206bde8308b2..5021d7c70aee 100644
> --- a/include/linux/crash_core.h
> +++ b/include/linux/crash_core.h
> @@ -69,6 +69,9 @@ extern unsigned char *vmcoreinfo_data;
>  extern size_t vmcoreinfo_size;
>  extern u32 *vmcoreinfo_note;
>  
> +extern struct resource crashk_res;
> +extern struct resource crashk_low_res;
> +
>  /* raw contents of kernel .notes section */
>  extern const void __start_notes __weak;
>  extern const void __stop_notes __weak;
> @@ -83,5 +86,6 @@ int parse_crashkernel_high(char *cmdline, unsigned long long system_ram,
>  		unsigned long long *crash_size, unsigned long long *crash_base);
>  int parse_crashkernel_low(char *cmdline, unsigned long long system_ram,
>  		unsigned long long *crash_size, unsigned long long *crash_base);
> +int __init reserve_crashkernel_low(void);
>  
>  #endif /* LINUX_CRASH_CORE_H */
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index 9e93bef52968..f301f2f5cfc4 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -337,8 +337,6 @@ extern int kexec_load_disabled;
>  
>  /* Location of a reserved region to hold the crash kernel.
>   */
> -extern struct resource crashk_res;
> -extern struct resource crashk_low_res;
>  extern note_buf_t __percpu *crash_notes;
>  
>  /* flag to track if kexec reboot is in progress */
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index 106e4500fd53..d39892bdb9ae 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -7,7 +7,12 @@
>  #include <linux/crash_core.h>
>  #include <linux/utsname.h>
>  #include <linux/vmalloc.h>
> +#include <linux/memblock.h>
> +#include <linux/swiotlb.h>
>  
> +#include <xen/xen.h>
> +
> +#include <asm/kexec.h>
>  #include <asm/page.h>
>  #include <asm/sections.h>
>  
> @@ -21,6 +26,22 @@ u32 *vmcoreinfo_note;
>  /* trusted vmcoreinfo, e.g. we can make a copy in the crash memory */
>  static unsigned char *vmcoreinfo_data_safecopy;
>  
> +/* Location of the reserved area for the crash kernel */
> +struct resource crashk_res = {
> +	.name  = "Crash kernel",
> +	.start = 0,
> +	.end   = 0,
> +	.flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM,
> +	.desc  = IORES_DESC_CRASH_KERNEL
> +};
> +struct resource crashk_low_res = {
> +	.name  = "Crash kernel",
> +	.start = 0,
> +	.end   = 0,
> +	.flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM,
> +	.desc  = IORES_DESC_CRASH_KERNEL
> +};
> +
>  /*
>   * parsing the "crashkernel" commandline
>   *
> @@ -294,6 +315,149 @@ int __init parse_crashkernel_low(char *cmdline,
>  				"crashkernel=", suffix_tbl[SUFFIX_LOW]);
>  }
>  
> +/*
> + * --------- Crashkernel reservation ------------------------------
> + */
> +
> +int __init reserve_crashkernel_low(void)

static?

> +{
> +#ifdef CONFIG_X86_64
> +	unsigned long long base, low_base = 0, low_size = 0;
> +	unsigned long low_mem_limit;
> +	int ret;
> +
> +	low_mem_limit = min(memblock_phys_mem_size(), CRASH_ADDR_LOW_MAX);
> +
> +	/* crashkernel=Y,low */
> +	ret = parse_crashkernel_low(boot_command_line, low_mem_limit, &low_size, &base);
> +	if (ret) {
> +		/*
> +		 * two parts from kernel/dma/swiotlb.c:
> +		 * -swiotlb size: user-specified with swiotlb= or default.
> +		 *
> +		 * -swiotlb overflow buffer: now hardcoded to 32k. We round it
> +		 * to 8M for other buffers that may need to stay low too. Also
> +		 * make sure we allocate enough extra low memory so that we
> +		 * don't run out of DMA buffers for 32-bit devices.
> +		 */
> +		low_size = max(swiotlb_size_or_default() + (8UL << 20), 256UL << 20);
> +	} else {
> +		/* passed with crashkernel=0,low ? */
> +		if (!low_size)
> +			return 0;
> +	}
> +
> +	low_base = memblock_phys_alloc_range(low_size, CRASH_ALIGN, CRASH_ALIGN,
> +			CRASH_ADDR_LOW_MAX);
> +	if (!low_base) {
> +		pr_err("Cannot reserve %ldMB crashkernel low memory, please try smaller size.\n",
> +		       (unsigned long)(low_size >> 20));
> +		return -ENOMEM;
> +	}
> +
> +	pr_info("Reserving %ldMB of low memory at %ldMB for crashkernel (low RAM limit: %ldMB)\n",
> +		(unsigned long)(low_size >> 20),
> +		(unsigned long)(low_base >> 20),
> +		(unsigned long)(low_mem_limit >> 20));
> +
> +	crashk_low_res.start = low_base;
> +	crashk_low_res.end   = low_base + low_size - 1;
> +	insert_resource(&iomem_resource, &crashk_low_res);
> +#endif
> +	return 0;
> +}
> +
> +#ifdef CONFIG_X86
> +#ifdef CONFIG_KEXEC_CORE
> +/*
> + * 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.
> + */
> +void __init reserve_crashkernel(void)
> +{
> +	unsigned long long crash_size, crash_base, total_mem;
> +	bool high = false;
> +	int ret;
> +
> +	total_mem = memblock_phys_mem_size();
> +
> +	/* crashkernel=XM */
> +	ret = parse_crashkernel(boot_command_line, total_mem, &crash_size, &crash_base);
> +	if (ret != 0 || crash_size <= 0) {
> +		/* crashkernel=X,high */
> +		ret = parse_crashkernel_high(boot_command_line, total_mem,
> +					     &crash_size, &crash_base);
> +		if (ret != 0 || crash_size <= 0)
> +			return;
> +		high = true;
> +	}
> +
> +	if (xen_pv_domain()) {
> +		pr_info("Ignoring crashkernel for a Xen PV domain\n");
> +		return;
> +	}
> +
> +	/* 0 means: find the address automatically */
> +	if (!crash_base) {
> +		/*
> +		 * Set CRASH_ADDR_LOW_MAX upper bound for crash memory,
> +		 * crashkernel=x,high reserves memory over CRASH_ADDR_LOW_MAX,
> +		 * also allocates 256M extra low memory for DMA buffers
> +		 * and swiotlb.
> +		 * But the extra memory is not required for all machines.
> +		 * So try low memory first and fall back to high memory
> +		 * unless "crashkernel=size[KMG],high" is specified.
> +		 */
> +		if (!high)
> +			crash_base = memblock_phys_alloc_range(crash_size,
> +						CRASH_ALIGN, CRASH_ALIGN,
> +						CRASH_ADDR_LOW_MAX);
> +		if (!crash_base)
> +			crash_base = memblock_phys_alloc_range(crash_size,
> +						CRASH_ALIGN, CRASH_ALIGN,
> +						CRASH_ADDR_HIGH_MAX);
> +		if (!crash_base) {
> +			pr_info("crashkernel reservation failed - No suitable area found.\n");
> +			return;
> +		}
> +	} else {
> +		/* User specifies base address explicitly. */
> +		unsigned long long start;
> +
> +		if (!IS_ALIGNED(crash_base, CRASH_ALIGN)) {
> +			pr_warn("cannot reserve crashkernel: base address is not %ldMB aligned\n",
> +				(unsigned long)CRASH_ALIGN >> 20);
> +			return;
> +		}
> +
> +		start = memblock_phys_alloc_range(crash_size, CRASH_ALIGN, crash_base,
> +						  crash_base + crash_size);
> +		if (start != crash_base) {
> +			pr_info("crashkernel reservation failed - memory is in use.\n");
> +			return;
> +		}
> +	}
> +
> +	if (crash_base >= CRASH_ADDR_LOW_MAX && reserve_crashkernel_low()) {
> +		memblock_free(crash_base, crash_size);
> +		return;
> +	}
> +
> +	pr_info("Reserving %ldMB of memory at %ldMB for crashkernel (System RAM: %ldMB)\n",
> +		(unsigned long)(crash_size >> 20),
> +		(unsigned long)(crash_base >> 20),
> +		(unsigned long)(total_mem >> 20));
> +
> +	crashk_res.start = crash_base;
> +	crashk_res.end   = crash_base + crash_size - 1;
> +	insert_resource(&iomem_resource, &crashk_res);
> +}
> +#endif /* CONFIG_KEXEC_CORE */
> +#endif
> +
>  Elf_Word *append_elf_note(Elf_Word *buf, char *name, unsigned int type,
>  			  void *data, size_t data_len)
>  {
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index 8798a8183974..2ca887514145 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -53,23 +53,6 @@ note_buf_t __percpu *crash_notes;
>  /* Flag to indicate we are going to kexec a new kernel */
>  bool kexec_in_progress = false;
>  
> -
> -/* Location of the reserved area for the crash kernel */
> -struct resource crashk_res = {
> -	.name  = "Crash kernel",
> -	.start = 0,
> -	.end   = 0,
> -	.flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM,
> -	.desc  = IORES_DESC_CRASH_KERNEL
> -};
> -struct resource crashk_low_res = {
> -	.name  = "Crash kernel",
> -	.start = 0,
> -	.end   = 0,
> -	.flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM,
> -	.desc  = IORES_DESC_CRASH_KERNEL
> -};
> -
>  int kexec_should_crash(struct task_struct *p)
>  {
>  	/*
> -- 
> 2.20.1
> 

-- 
Sincerely yours,
Mike.

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