Re: [PATCH v11 2/5] x86: kdump: move reserve_crashkernel_low() into crash_core.c

Dave Young
2020-08-08T10:00:19Z

On 08/01/20 at 09:08pm, Chen Zhou wrote:
> In preparation for supporting reserve_crashkernel_low in arm64 as
> x86_64 does, move reserve_crashkernel_low() into kernel/crash_core.c.
>
> BTW, move x86_64 CRASH_ALIGN to 2M suggested by Dave. CONFIG_PHYSICAL_ALIGN
> can be selected from 2M to 16M, move to the same as arm64.
>
> Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
> ---
> arch/x86/include/asm/kexec.h | 24 ++++++++++
> arch/x86/kernel/setup.c | 86 +++---------------------------------
> include/linux/crash_core.h | 3 ++
> include/linux/kexec.h | 2 -
> kernel/crash_core.c | 74 +++++++++++++++++++++++++++++++
> kernel/kexec_core.c | 17 -------
> 6 files changed, 107 insertions(+), 99 deletions(-)
>
> diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
> index 6802c59e8252..f8f9d952e09f 100644
> --- a/arch/x86/include/asm/kexec.h
> +++ b/arch/x86/include/asm/kexec.h
> @@ -18,6 +18,30 @@
>
> # define KEXEC_CONTROL_CODE_MAX_SIZE 2048
>
> +/* 2M alignment for crash kernel regions */
> +#define CRASH_ALIGN SZ_2M
> +
> +/*
> + * 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>
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index a3767e74c758..46763c1e5d9f 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -401,83 +401,6 @@ static void __init memblock_x86_reserve_range_setup_data(void)
>
> #ifdef CONFIG_KEXEC_CORE
>
> -/* 16M 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
> -
> -static int __init reserve_crashkernel_low(void)
> -{
> -#ifdef CONFIG_X86_64
> - unsigned long long base, low_base = 0, low_size = 0;
> - unsigned long total_low_mem;
> - int ret;
> -
> - total_low_mem = memblock_mem_size(1UL << (32 - PAGE_SHIFT));
> -
> - /* crashkernel=Y,low */
> - ret = parse_crashkernel_low(boot_command_line, total_low_mem, &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_find_in_range(0, 1ULL << 32, low_size, CRASH_ALIGN);
> - if (!low_base) {
> - pr_err("Cannot reserve %ldMB crashkernel low memory, please try smaller size.\n",
> - (unsigned long)(low_size >> 20));
> - return -ENOMEM;
> - }
> -
> - ret = memblock_reserve(low_base, low_size);
> - if (ret) {
> - pr_err("%s: Error reserving crashkernel low memblock.\n", __func__);
> - return ret;
> - }
> -
> - pr_info("Reserving %ldMB of low memory at %ldMB for crashkernel (System low RAM: %ldMB)\n",
> - (unsigned long)(low_size >> 20),
> - (unsigned long)(low_base >> 20),
> - (unsigned long)(total_low_mem >> 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;
> @@ -541,9 +464,12 @@ static void __init reserve_crashkernel(void)
> return;
> }
>
> - if (crash_base >= (1ULL << 32) && reserve_crashkernel_low()) {
> - memblock_free(crash_base, crash_size);
> - return;
> + if (crash_base >= (1ULL << 32)) {
> + if (reserve_crashkernel_low()) {
> + memblock_free(crash_base, crash_size);
> + return;
> + }
> + insert_resource(&iomem_resource, &crashk_low_res);
> }
>
> pr_info("Reserving %ldMB of memory at %ldMB for crashkernel (System RAM: %ldMB)\n",
> diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
> index 525510a9f965..4df8c0bff03e 100644
> --- a/include/linux/crash_core.h
> +++ b/include/linux/crash_core.h
> @@ -63,6 +63,8 @@ phys_addr_t paddr_vmcoreinfo_note(void);
> 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;
>
> Elf_Word *append_elf_note(Elf_Word *buf, char *name, unsigned int type,
> void *data, size_t data_len);
> @@ -74,5 +76,6 @@ 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 ea67910ae6b7..a460afdbab0f 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -330,8 +330,6 @@ 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 9f1557b98468..c81b15dd78c2 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -7,7 +7,10 @@
> #include <linux/crash_core.h>
> #include <linux/utsname.h>
> #include <linux/vmalloc.h>
> +#include <linux/memblock.h>
> +#include <linux/swiotlb.h>
>
> +#include <asm/kexec.h>
> #include <asm/page.h>
> #include <asm/sections.h>
>
> @@ -19,6 +22,22 @@ 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
> *
> @@ -292,6 +311,61 @@ int __init parse_crashkernel_low(char *cmdline,
> "crashkernel=", suffix_tbl[SUFFIX_LOW]);
> }
>
> +int __init reserve_crashkernel_low(void)
> +{
> +#if defined(CONFIG_X86_64) || defined(CONFIG_ARM64)
> + unsigned long long base, low_base = 0, low_size = 0;
> + unsigned long total_low_mem;
> + int ret;
> +
> + total_low_mem = memblock_mem_size(CRASH_ADDR_LOW_MAX >> PAGE_SHIFT);
> +
> + /* crashkernel=Y,low */
> + ret = parse_crashkernel_low(boot_command_line, total_low_mem, &low_size,
> + &base);
> + if (ret) {
> + /*
> + * two parts from lib/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_find_in_range(0, CRASH_ADDR_LOW_MAX, low_size, CRASH_ALIGN);
> + if (!low_base) {
> + pr_err("Cannot reserve %ldMB crashkernel low memory, please try smaller size.\n",
> + (unsigned long)(low_size >> 20));
> + return -ENOMEM;
> + }
> +
> + ret = memblock_reserve(low_base, low_size);
> + if (ret) {
> + pr_err("%s: Error reserving crashkernel low memblock.\n",
> + __func__);
> + return ret;
> + }
> +
> + pr_info("Reserving %ldMB of low memory at %ldMB for crashkernel (System low RAM: %ldMB)\n",
> + (unsigned long)(low_size >> 20),
> + (unsigned long)(low_base >> 20),
> + (unsigned long)(total_low_mem >> 20));
> +
> + crashk_low_res.start = low_base;
> + crashk_low_res.end = low_base + low_size - 1;
> +#endif
> + return 0;
> +}
> +
> 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 c19c0dad1ebe..db66bbabfff3 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
>

Acked-by: Dave Young <dyoung@redhat.com>

Thanks
Dave