[PATCH v2 2/3] RISC-V: Add kdump support
Palmer Dabbelt
palmer at dabbelt.com
Fri Jul 10 23:59:16 EDT 2020
On Tue, 23 Jun 2020 08:05:11 PDT (-0700), mick at ics.forth.gr wrote:
> This patch adds support for kdump, the kernel will reserve a
> region for the crash kernel and jump there on panic. In order
> for userspace tools (kexec-tools) to prepare the crash kernel
> kexec image, we also need to expose some information on
> /proc/iomem for the memory regions used by the kernel and for
> the region reserved for crash kernel. Note that on userspace
> the device tree is used to determine the system's memory
> layout so the "System RAM" on /proc/iomem is ignored. I just
> put it there for compatibility with other archs.
>
> I tested this on riscv64 qemu and works as expected, you may
> test it by triggering a crash through /proc/sysrq_trigger:
>
> echo c > /proc/sysrq_trigger
>
> v2:
> * Properly populate the ioresources tree, so that it can be
> used later on for implementing strict /dev/mem.
> * Minor cleanups and re-base
>
> Signed-off-by: Nick Kossifidis <mick at ics.forth.gr>
> ---
> arch/riscv/include/asm/kexec.h | 19 ++-
> arch/riscv/include/uapi/asm/elf.h | 6 +
> arch/riscv/kernel/Makefile | 2 +-
> arch/riscv/kernel/crash_save_regs.S | 56 +++++++++
> arch/riscv/kernel/kexec_relocate.S | 61 +++++++++-
> arch/riscv/kernel/machine_kexec.c | 31 +++--
> arch/riscv/kernel/setup.c | 180 ++++++++++++++++++++++++++++
> arch/riscv/mm/init.c | 77 ++++++++++++
> 8 files changed, 411 insertions(+), 21 deletions(-)
> create mode 100644 arch/riscv/kernel/crash_save_regs.S
>
> diff --git a/arch/riscv/include/asm/kexec.h b/arch/riscv/include/asm/kexec.h
> index efc69feb4..4fd583acc 100644
> --- a/arch/riscv/include/asm/kexec.h
> +++ b/arch/riscv/include/asm/kexec.h
> @@ -21,11 +21,16 @@
>
> #define KEXEC_ARCH KEXEC_ARCH_RISCV
>
> +extern void riscv_crash_save_regs(struct pt_regs *newregs);
> +
> static inline void
> crash_setup_regs(struct pt_regs *newregs,
> struct pt_regs *oldregs)
> {
> - /* Dummy implementation for now */
> + if (oldregs)
> + memcpy(newregs, oldregs, sizeof(struct pt_regs));
> + else
> + riscv_crash_save_regs(newregs);
> }
>
>
> @@ -38,10 +43,12 @@ struct kimage_arch {
> const extern unsigned char riscv_kexec_relocate[];
> const extern unsigned int riscv_kexec_relocate_size;
>
> -typedef void (*riscv_kexec_do_relocate)(unsigned long first_ind_entry,
> - unsigned long jump_addr,
> - unsigned long fdt_addr,
> - unsigned long hartid,
> - unsigned long va_pa_off);
> +typedef void (*riscv_kexec_method)(unsigned long first_ind_entry,
> + unsigned long jump_addr,
> + unsigned long fdt_addr,
> + unsigned long hartid,
> + unsigned long va_pa_off);
> +
> +extern riscv_kexec_method riscv_kexec_norelocate;
>
> #endif
> diff --git a/arch/riscv/include/uapi/asm/elf.h b/arch/riscv/include/uapi/asm/elf.h
> index d696d6610..5b19f5547 100644
> --- a/arch/riscv/include/uapi/asm/elf.h
> +++ b/arch/riscv/include/uapi/asm/elf.h
> @@ -19,6 +19,12 @@ typedef unsigned long elf_greg_t;
> typedef struct user_regs_struct elf_gregset_t;
> #define ELF_NGREG (sizeof(elf_gregset_t) / sizeof(elf_greg_t))
>
> +#define ELF_CORE_COPY_REGS(dest, regs) \
> +do { \
> + *(struct user_regs_struct *)&(dest) = \
> + *(struct user_regs_struct *)regs; \
> +} while (0);
> +
> /* We don't support f without d, or q. */
> typedef __u64 elf_fpreg_t;
> typedef union __riscv_fp_state elf_fpregset_t;
> diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
> index 63fc530a4..b9a3842ad 100644
> --- a/arch/riscv/kernel/Makefile
> +++ b/arch/riscv/kernel/Makefile
> @@ -52,6 +52,6 @@ obj-$(CONFIG_SMP) += cpu_ops_sbi.o
> endif
> obj-$(CONFIG_HOTPLUG_CPU) += cpu-hotplug.o
> obj-$(CONFIG_KGDB) += kgdb.o
> -obj-${CONFIG_KEXEC} += kexec_relocate.o machine_kexec.o
> +obj-${CONFIG_KEXEC} += kexec_relocate.o crash_save_regs.o machine_kexec.o
>
> clean:
> diff --git a/arch/riscv/kernel/crash_save_regs.S b/arch/riscv/kernel/crash_save_regs.S
> new file mode 100644
> index 000000000..7832fb763
> --- /dev/null
> +++ b/arch/riscv/kernel/crash_save_regs.S
> @@ -0,0 +1,56 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2020 FORTH-ICS/CARV
> + * Nick Kossifidis <mick at ics.forth.gr>
> + */
> +
> +#include <asm/asm.h> /* For RISCV_* and REG_* macros */
> +#include <asm/csr.h> /* For CSR_* macros */
> +#include <asm/asm-offsets.h> /* For offsets on pt_regs */
> +#include <linux/linkage.h> /* For SYM_* macros */
> +
> +.section ".text"
> +SYM_CODE_START(riscv_crash_save_regs)
> + REG_S ra, PT_RA(a0) /* x1 */
> + REG_S sp, PT_SP(a0) /* x2 */
> + REG_S gp, PT_GP(a0) /* x3 */
> + REG_S tp, PT_TP(a0) /* x4 */
> + REG_S t0, PT_T0(a0) /* x5 */
> + REG_S t1, PT_T1(a0) /* x6 */
> + REG_S t2, PT_T2(a0) /* x7 */
> + REG_S s0, PT_S0(a0) /* x8/fp */
> + REG_S s1, PT_S1(a0) /* x9 */
> + REG_S a0, PT_A0(a0) /* x10 */
> + REG_S a1, PT_A1(a0) /* x11 */
> + REG_S a2, PT_A2(a0) /* x12 */
> + REG_S a3, PT_A3(a0) /* x13 */
> + REG_S a4, PT_A4(a0) /* x14 */
> + REG_S a5, PT_A5(a0) /* x15 */
> + REG_S a6, PT_A6(a0) /* x16 */
> + REG_S a7, PT_A7(a0) /* x17 */
> + REG_S s2, PT_S2(a0) /* x18 */
> + REG_S s3, PT_S3(a0) /* x19 */
> + REG_S s4, PT_S4(a0) /* x20 */
> + REG_S s5, PT_S5(a0) /* x21 */
> + REG_S s6, PT_S6(a0) /* x22 */
> + REG_S s7, PT_S7(a0) /* x23 */
> + REG_S s8, PT_S8(a0) /* x24 */
> + REG_S s9, PT_S9(a0) /* x25 */
> + REG_S s10, PT_S10(a0) /* x26 */
> + REG_S s11, PT_S11(a0) /* x27 */
> + REG_S t3, PT_T3(a0) /* x28 */
> + REG_S t4, PT_T4(a0) /* x29 */
> + REG_S t5, PT_T5(a0) /* x30 */
> + REG_S t6, PT_T6(a0) /* x31 */
> +
> + csrr t1, CSR_STATUS
> + csrr t2, CSR_EPC
> + csrr t3, CSR_TVAL
> + csrr t4, CSR_CAUSE
> +
> + REG_S t1, PT_STATUS(a0)
> + REG_S t2, PT_EPC(a0)
> + REG_S t3, PT_BADADDR(a0)
> + REG_S t4, PT_CAUSE(a0)
> + ret
> +SYM_CODE_END(riscv_crash_save_regs)
> diff --git a/arch/riscv/kernel/kexec_relocate.S b/arch/riscv/kernel/kexec_relocate.S
> index cd17d585f..c417c44ea 100644
> --- a/arch/riscv/kernel/kexec_relocate.S
> +++ b/arch/riscv/kernel/kexec_relocate.S
> @@ -152,7 +152,66 @@ SYM_CODE_START(riscv_kexec_relocate)
> SYM_CODE_END(riscv_kexec_relocate)
> riscv_kexec_relocate_end:
>
> - .section ".rodata"
> +
> +/* Used for jumping to crashkernel */
> +.section ".text"
> +SYM_CODE_START(riscv_kexec_norelocate)
> + /*
> + * s0: (const) Phys address to jump to
> + * s1: (const) Phys address of the FDT image
> + * s2: (const) The hartid of the current hart
> + */
> + mv s0, a1
> + mv s1, a2
> + mv s2, a3
> +
> + /* Disable / cleanup interrupts */
> + csrw sie, zero
> + csrw sip, zero
> +
> + /* Switch to physical addressing */
> + csrw sptbr, zero
I guess I'm missing something, but I'd assume that we would need some sort of
tvec juggling here like we usually do when jumping between virtual and physical
spaces. I get that we're not relocating the kernel that we're jumping to, but
I don't understand how PAGE_OFFSET works.
> +
> + /* Pass the arguments to the next kernel / Cleanup*/
Missing space in that comment.
> + mv a0, s2
> + mv a1, s1
> + mv a2, s0
> +
> + /* Cleanup */
> + mv a3, zero
> + mv a4, zero
> + mv a5, zero
> + mv a6, zero
> + mv a7, zero
> +
> + mv s0, zero
> + mv s1, zero
> + mv s2, zero
> + mv s3, zero
> + mv s4, zero
> + mv s5, zero
> + mv s6, zero
> + mv s7, zero
> + mv s8, zero
> + mv s9, zero
> + mv s10, zero
> + mv s11, zero
> +
> + mv t0, zero
> + mv t1, zero
> + mv t2, zero
> + mv t3, zero
> + mv t4, zero
> + mv t5, zero
> + mv t6, zero
> + csrw sepc, zero
> + csrw scause, zero
> + csrw sscratch, zero
> +
> + jalr zero, a2, 0
> +SYM_CODE_END(riscv_kexec_norelocate)
> +
> +.section ".rodata"
> SYM_DATA(riscv_kexec_relocate_size,
> .long riscv_kexec_relocate_end - riscv_kexec_relocate)
>
> diff --git a/arch/riscv/kernel/machine_kexec.c b/arch/riscv/kernel/machine_kexec.c
> index 88734a056..dfe6e9066 100644
> --- a/arch/riscv/kernel/machine_kexec.c
> +++ b/arch/riscv/kernel/machine_kexec.c
> @@ -58,11 +58,6 @@ machine_kexec_prepare(struct kimage *image)
>
> kexec_image_info(image);
>
> - if (image->type == KEXEC_TYPE_CRASH) {
> - pr_warn("Loading a crash kernel is unsupported for now.\n");
> - return -EINVAL;
> - }
> -
> /* Find the Flattened Device Tree and save its physical address */
> for (i = 0; i < image->nr_segments; i++) {
> if (image->segment[i].memsz <= sizeof(fdt))
> @@ -84,12 +79,14 @@ machine_kexec_prepare(struct kimage *image)
> }
>
> /* Copy the assembler code for relocation to the control page */
> - control_code_buffer = page_address(image->control_code_page);
> - memcpy(control_code_buffer, riscv_kexec_relocate,
> - riscv_kexec_relocate_size);
> + if (image->type != KEXEC_TYPE_CRASH) {
> + control_code_buffer = page_address(image->control_code_page);
> + memcpy(control_code_buffer, riscv_kexec_relocate,
> + riscv_kexec_relocate_size);
>
> - /* Mark the control page executable */
> - set_memory_x((unsigned long) control_code_buffer, 1);
> + /* Mark the control page executable */
> + set_memory_x((unsigned long) control_code_buffer, 1);
> + }
>
> #ifdef CONFIG_SMP
> /*
> @@ -149,6 +146,9 @@ void machine_shutdown(void)
> void
> machine_crash_shutdown(struct pt_regs *regs)
> {
> + crash_save_cpu(regs, smp_processor_id());
> + machine_shutdown();
> + pr_info("Starting crashdump kernel...\n");
> }
>
> /**
> @@ -171,7 +171,12 @@ machine_kexec(struct kimage *image)
> unsigned long this_hart_id = raw_smp_processor_id();
> unsigned long fdt_addr = internal->fdt_addr;
> void *control_code_buffer = page_address(image->control_code_page);
> - riscv_kexec_do_relocate do_relocate = control_code_buffer;
> + riscv_kexec_method kexec_method = NULL;
> +
> + if (image->type != KEXEC_TYPE_CRASH)
> + kexec_method = control_code_buffer;
> + else
> + kexec_method = (riscv_kexec_method) &riscv_kexec_norelocate;
>
> pr_notice("Will call new kernel at %08lx from hart id %lx\n",
> jump_addr, this_hart_id);
> @@ -182,7 +187,7 @@ machine_kexec(struct kimage *image)
>
> /* Jump to the relocation code */
> pr_notice("Bye...\n");
> - do_relocate(first_ind_entry, jump_addr, fdt_addr,
> - this_hart_id, va_pa_offset);
> + kexec_method(first_ind_entry, jump_addr, fdt_addr,
> + this_hart_id, va_pa_offset);
> unreachable();
> }
> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index f04373be5..4dc940389 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -4,6 +4,8 @@
> * Chen Liqin <liqin.chen at sunplusct.com>
> * Lennox Wu <lennox.wu at sunplusct.com>
> * Copyright (C) 2012 Regents of the University of California
> + * Copyright (C) 2020 FORTH-ICS/CARV
> + * Nick Kossifidis <mick at ics.forth.gr>
> */
>
> #include <linux/init.h>
> @@ -17,6 +19,8 @@
> #include <linux/sched/task.h>
> #include <linux/swiotlb.h>
> #include <linux/smp.h>
> +#include <linux/crash_dump.h>
> +#include <linux/initrd.h>
>
> #include <asm/clint.h>
> #include <asm/cpu_ops.h>
> @@ -49,6 +53,181 @@ atomic_t hart_lottery __section(.sdata);
> unsigned long boot_cpu_hartid;
> static DEFINE_PER_CPU(struct cpu, cpu_devices);
>
> +/*
> + * Place kernel memory regions on the resource tree so that
> + * kexec-tools can retrieve them from /proc/iomem. While there
> + * also add "System RAM" regions for compatibility with other
> + * archs, and the rest of the known regions for completeness.
> + */
> +static struct resource code_res = { .name = "Kernel code", };
> +static struct resource data_res = { .name = "Kernel data", };
> +static struct resource rodata_res = { .name = "Kernel rodata", };
> +static struct resource bss_res = { .name = "Kernel bss", };
> +
> +static int __init add_resource(struct resource *parent,
> + struct resource *res)
> +{
> + int ret = 0;
> +
> + ret = insert_resource(parent, res);
> + if (ret < 0) {
> + pr_err("Failed to add a %s resource at %llx\n",
> + res->name, res->start);
> + return ret;
> + }
> +
> + return 1;
> +}
> +
> +static int __init add_kernel_resources(struct resource *res)
> +{
> + int ret = 0;
> +
> + /*
> + * The memory region of the kernel image is continuous and
> + * was reserved on setup_bootmem, find it here and register
> + * it as a resource, then register the various segments of
> + * the image as child nodes
> + */
> + if (!(res->start <= code_res.start && res->end >= data_res.end))
> + return 0;
> +
> + res->name = "Kernel image";
> + res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> +
> + /*
> + * We removed a part of this region on setup_bootmem so
> + * we need to expand the resource for the bss to fit in.
> + */
> + res->end = bss_res.end;
> +
> + ret = add_resource(&iomem_resource, res);
> + if (ret < 0)
> + return ret;
> +
> + ret = add_resource(res, &code_res);
> + if (ret < 0)
> + return ret;
> +
> + ret = add_resource(res, &rodata_res);
> + if (ret < 0)
> + return ret;
> +
> + ret = add_resource(res, &data_res);
> + if (ret < 0)
> + return ret;
> +
> + ret = add_resource(res, &bss_res);
> +
> + return ret;
> +}
> +
> +#ifdef CONFIG_KEXEC_CORE
> +static int __init add_crashk_resource(struct resource *res)
> +{
> + if (res->start <= crashk_res.start && res->end >= crashk_res.end)
> + return add_resource(&iomem_resource, &crashk_res);
> +
> + return 0;
> +}
> +#endif
> +
> +static void __init init_resources(void)
> +{
> + struct memblock_region *region = NULL;
> + struct resource *res = NULL;
> + int ret = 0;
> +
> + code_res.start = __pa_symbol(_text);
> + code_res.end = __pa_symbol(_etext) - 1;
> + code_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> +
> + rodata_res.start = __pa_symbol(__start_rodata);
> + rodata_res.end = __pa_symbol(__end_rodata) - 1;
> + rodata_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> +
> + data_res.start = __pa_symbol(_data);
> + data_res.end = __pa_symbol(_edata) - 1;
> + data_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> +
> + bss_res.start = __pa_symbol(__bss_start);
> + bss_res.end = __pa_symbol(__bss_stop) - 1;
> + bss_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> +
> + /*
> + * Start by adding the reserved regions, if they overlap
> + * with /memory regions, insert_resource later on will take
> + * care of it.
> + */
> + for_each_memblock(reserved, region) {
> + res = memblock_alloc(sizeof(struct resource), SMP_CACHE_BYTES);
> + if (!res)
> + panic("%s: Failed to allocate %zu bytes\n", __func__,
> + sizeof(struct resource));
> +
> + res->name = "Reserved";
> + res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
> + res->start = __pfn_to_phys(memblock_region_reserved_base_pfn(region));
> + res->end = __pfn_to_phys(memblock_region_reserved_end_pfn(region)) - 1;
> +
> + ret = add_kernel_resources(res);
> + if (ret < 0)
> + goto error;
> + else if (ret)
> + continue;
> +
> +#ifdef CONFIG_KEXEC_CORE
> + ret = add_crashk_resource(res);
> + if (ret < 0)
> + goto error;
> + else if (ret)
> + continue;
> +#endif
> +
> + /*
> + * Ignore any other reserved regions within
> + * system memory.
> + */
> + if (memblock_is_memory(res->start))
> + continue;
> +
> + ret = add_resource(&iomem_resource, res);
> + if (ret < 0)
> + goto error;
> + }
> +
> + /* Add /memory regions to the resource tree */
> + for_each_memblock(memory, region) {
> + res = memblock_alloc(sizeof(struct resource), SMP_CACHE_BYTES);
> + if (!res)
> + panic("%s: Failed to allocate %zu bytes\n", __func__,
> + sizeof(struct resource));
> +
> + if (unlikely(memblock_is_nomap(region))) {
> + res->name = "Reserved";
> + res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
This differs from what I ended up with in that I don't have IORESOURCE_BUSY. I
just copied this blindly from arm64 so I don't actually know what the
difference is.
> + } else {
> + res->name = "System RAM";
> + res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> + }
> +
> + res->start = __pfn_to_phys(memblock_region_memory_base_pfn(region));
> + res->end = __pfn_to_phys(memblock_region_memory_end_pfn(region)) - 1;
> +
> + ret = add_resource(&iomem_resource, res);
> + if (ret < 0)
> + goto error;
> + }
> +
> + return;
> +
> + error:
> + memblock_free((phys_addr_t) res, sizeof(struct resource));
> + /* Better an empty resource tree than an inconsistent one */
> + release_child_resources(&iomem_resource);
> +}
> +
> +
> void __init parse_dtb(void)
> {
> if (early_init_dt_scan(dtb_early_va))
> @@ -74,6 +253,7 @@ void __init setup_arch(char **cmdline_p)
>
> setup_bootmem();
> paging_init();
> + init_resources();
> #if IS_ENABLED(CONFIG_BUILTIN_DTB)
> unflatten_and_copy_device_tree();
> #else
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index f4adb3684..e4ce3a2af 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -2,6 +2,8 @@
> /*
> * Copyright (C) 2012 Regents of the University of California
> * Copyright (C) 2019 Western Digital Corporation or its affiliates.
> + * Copyright (C) 2020 FORTH-ICS/CARV
> + * Nick Kossifidis <mick at ics.forth.gr>
> */
>
> #include <linux/init.h>
> @@ -13,6 +15,7 @@
> #include <linux/of_fdt.h>
> #include <linux/libfdt.h>
> #include <linux/set_memory.h>
> +#include <linux/crash_dump.h>
>
> #include <asm/fixmap.h>
> #include <asm/tlbflush.h>
> @@ -517,6 +520,77 @@ void mark_rodata_ro(void)
> }
> #endif
>
> +#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.
> + */
> +static void __init reserve_crashkernel(void)
> +{
> + unsigned long long crash_base = 0;
> + unsigned long long crash_size = 0;
> + unsigned long search_start = memblock_start_of_DRAM();
> + unsigned long search_end = memblock_end_of_DRAM();
> +
> + int ret = 0;
> +
> + ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
> + &crash_size, &crash_base);
> + if (ret || !crash_size)
> + return;
> +
> + crash_size = PAGE_ALIGN(crash_size);
> +
> + if (crash_base == 0) {
> + /*
> + * Current riscv boot protocol requires 2MB alignment for
> + * RV64 and 4MB alignment for RV32 (hugepage size)
> + */
> + crash_base = memblock_find_in_range(search_start, search_end,
> +#ifdef CONFIG_64BIT
> + crash_size, SZ_2M);
> +#else
> + crash_size, SZ_4M);
> +#endif
> + if (crash_base == 0) {
> + pr_warn("crashkernel: couldn't allocate %lldKB\n",
> + crash_size >> 10);
> + return;
> + }
> + } else {
> + /* User specifies base address explicitly. */
> + if (!memblock_is_region_memory(crash_base, crash_size)) {
> + pr_warn("crashkernel: requested region is not memory\n");
> + return;
> + }
> +
> + if (memblock_is_region_reserved(crash_base, crash_size)) {
> + pr_warn("crashkernel: requested region is reserved\n");
> + return;
> + }
> +
> +#ifdef CONFIG_64BIT
> + if (!IS_ALIGNED(crash_base, SZ_2M)) {
> +#else
> + if (!IS_ALIGNED(crash_base, SZ_4M)) {
> +#endif
> + pr_warn("crashkernel: requested region is misaligned\n");
> + return;
> + }
> + }
> + memblock_reserve(crash_base, crash_size);
> +
> + pr_info("crashkernel: reserved 0x%016llx - 0x%016llx (%lld MB)\n",
> + crash_base, crash_base + crash_size, crash_size >> 20);
> +
> + crashk_res.start = crash_base;
> + crashk_res.end = crash_base + crash_size - 1;
> +}
> +#endif
> +
> void __init paging_init(void)
> {
> setup_vm_final();
> @@ -524,6 +598,9 @@ void __init paging_init(void)
> sparse_init();
> setup_zero_page();
> zone_sizes_init();
> +#ifdef CONFIG_KEXEC_CORE
> + reserve_crashkernel();
> +#endif
> }
>
> #ifdef CONFIG_SPARSEMEM_VMEMMAP
Reviewed-by: Palmer Dabbelt <palmerdabbelt at google.com>
If you split out init_resource() then I can take it before the rest of the
kexec stuff.
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