On 12/11/23 at 02:00pm, Sourabh Jain wrote:
......
> diff --git a/arch/powerpc/include/asm/kexec_ranges.h
> b/arch/powerpc/include/asm/kexec_ranges.h
> index f83866a19e87..802abf580cf0 100644
> --- a/arch/powerpc/include/asm/kexec_ranges.h
> +++ b/arch/powerpc/include/asm/kexec_ranges.h
> @@ -7,6 +7,7 @@
> void sort_memory_ranges(struct crash_mem *mrngs, bool merge);
> struct crash_mem *realloc_mem_ranges(struct crash_mem **mem_ranges);
> int add_mem_range(struct crash_mem **mem_ranges, u64 base, u64 size);
> +int remove_mem_range(struct crash_mem **mem_ranges, u64 base, u64 size);
> int add_tce_mem_ranges(struct crash_mem **mem_ranges);
> int add_initrd_mem_range(struct crash_mem **mem_ranges);
> #ifdef CONFIG_PPC_64S_HASH_MMU
> diff --git a/arch/powerpc/kexec/core_64.c b/arch/powerpc/kexec/core_64.c
> index 9932793cd64b..5be30659172f 100644
> --- a/arch/powerpc/kexec/core_64.c
> +++ b/arch/powerpc/kexec/core_64.c
> @@ -19,8 +19,11 @@
> #include <linux/of.h>
> #include <linux/libfdt.h>
> #include <linux/memblock.h>
> +#include <linux/memory.h>
>
> #include <asm/page.h>
> +#include <asm/drmem.h>
> +#include <asm/mmzone.h>
> #include <asm/current.h>
> #include <asm/machdep.h>
> #include <asm/cacheflush.h>
> @@ -547,9 +550,7 @@ int update_cpus_node(void *fdt)
> #undef pr_fmt
> #define pr_fmt(fmt) "crash hp: " fmt
>
> -#ifdef CONFIG_HOTPLUG_CPU
> - /* Provides the value for the sysfs crash_hotplug nodes */
> -int arch_crash_hotplug_cpu_support(struct kimage *image)
> +static int crash_hotplug_support(struct kimage *image)
> {
> if (image->file_mode)
> return 1;
> @@ -560,8 +561,118 @@ int arch_crash_hotplug_cpu_support(struct kimage *image)
> */
> return image->update_elfcorehdr && image->update_fdt;
> }
> +
> +#ifdef CONFIG_HOTPLUG_CPU
> + /* Provides the value for the sysfs crash_hotplug nodes */
> +int arch_crash_hotplug_cpu_support(struct kimage *image)
> +{
> + return crash_hotplug_support(image);
> +}
> +#endif
> +
> +#ifdef CONFIG_MEMORY_HOTPLUG
> + /* Provides the value for the sysfs memory_hotplug nodes */
> +int arch_crash_hotplug_memory_support(struct kimage *image)
> +{
> + return crash_hotplug_support(image);
> +}
> #endif
>
> +/*
> + * Advertise preferred elfcorehdr size to userspace via
> + * /sys/kernel/crash_elfcorehdr_size sysfs interface.
> + */
> +unsigned int arch_crash_get_elfcorehdr_size(void)
> +{
> + unsigned int sz;
> + unsigned long elf_phdr_cnt;
> +
> + /* Program header for CPU notes and vmcoreinfo */
> + elf_phdr_cnt = 2;
> + if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
> + /* In the worst case, a Phdr is needed for every other LMB to be
> + * represented as an individual crash range.
> + */
> + elf_phdr_cnt += memory_hotplug_max() / (2 * drmem_lmb_size());
> +
> + /* Do not cross the max limit */
> + if (elf_phdr_cnt > PN_XNUM)
> + elf_phdr_cnt = PN_XNUM;
> +
> + sz = sizeof(struct elfhdr) + (elf_phdr_cnt * sizeof(Elf64_Phdr));
> + return sz;
> +}
> +
> +/**
> + * update_crash_elfcorehdr() - Recreate the elfcorehdr and replace it with
> old
> + * elfcorehdr in the kexec segment array.
> + * @image: the active struct kimage
> + * @mn: struct memory_notify data handler
> + */
> +static void update_crash_elfcorehdr(struct kimage *image, struct
> memory_notify *mn)
> +{
> + int ret;
> + struct crash_mem *cmem = NULL;
> + struct kexec_segment *ksegment;
> + void *ptr, *mem, *elfbuf = NULL;
> + unsigned long elfsz, memsz, base_addr, size;
> +
> + ksegment = &image->segment[image->elfcorehdr_index];
> + mem = (void *) ksegment->mem;
> + memsz = ksegment->memsz;
> +
> + ret = get_crash_memory_ranges(&cmem);
> + if (ret) {
> + pr_err("Failed to get crash mem range\n");
> + return;
> + }
> +
> + /*
> + * The hot unplugged memory is part of crash memory ranges,
> + * remove it here.
> + */
> + if (image->hp_action == KEXEC_CRASH_HP_REMOVE_MEMORY) {
> + base_addr = PFN_PHYS(mn->start_pfn);
> + size = mn->nr_pages * PAGE_SIZE;
> + ret = remove_mem_range(&cmem, base_addr, size);
Althouth this is ppc specific, I don't understand. Why don't you
recreate the elfcorehdr, but take removing the removed region. Comparing the
remove_mem_range() implementation with recreating, I don't see too much
benefit from that, and it makes your code more complicated. Just
curious, surely ppc people can decide what should be taken.
> + if (ret) {
> + pr_err("Failed to remove hot-unplugged from crash
> memory ranges.\n");
> + return;
> + }
> + }
> +
> + ret = crash_prepare_elf64_headers(cmem, false, &elfbuf, &elfsz);
> + if (ret) {
> + pr_err("Failed to prepare elf header\n");
> + return;
> + }
> +
> + /*
> + * It is unlikely that kernel hit this because elfcorehdr kexec
> + * segment (memsz) is built with addition space to accommodate growing
> + * number of crash memory ranges while loading the kdump kernel. It is
> + * Just to avoid any unforeseen case.
> + */
> + if (elfsz > memsz) {
> + pr_err("Updated crash elfcorehdr elfsz %lu > memsz %lu", elfsz,
> memsz);
> + goto out;
> + }
> +
> + ptr = __va(mem);
> + if (ptr) {
> + /* Temporarily invalidate the crash image while it is replaced
> */
> + xchg(&kexec_crash_image, NULL);
> +
> + /* Replace the old elfcorehdr with newly prepared elfcorehdr */
> + memcpy((void *)ptr, elfbuf, elfsz);
> +
> + /* The crash image is now valid once again */
> + xchg(&kexec_crash_image, image);
> + }
> +out:
> + vfree(elfbuf);
> +}
> +
> /**
> * arch_crash_handle_hotplug_event - Handle crash CPU/Memory hotplug events
> to update the
> * necessary kexec segments based on the
> hotplug event.
> @@ -572,7 +683,7 @@ int arch_crash_hotplug_cpu_support(struct kimage *image)
> * CPU addition: Update the FDT segment to include the newly added CPU.
> * CPU removal: No action is needed, with the assumption that it's okay to
> have offline CPUs
> * as part of the FDT.
> - * Memory addition/removal: No action is taken as this is not yet supported.
> + * Memory addition/removal: Recreate the elfcorehdr segment
> */
> void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)
> {
> @@ -593,7 +704,6 @@ void arch_crash_handle_hotplug_event(struct kimage
> *image, void *arg)
> return;
>
> } else if (hp_action == KEXEC_CRASH_HP_ADD_CPU) {
> -
> void *fdt, *ptr;
> unsigned long mem;
> int i, fdt_index = -1;
> @@ -628,8 +738,10 @@ void arch_crash_handle_hotplug_event(struct kimage
> *image, void *arg)
>
> } else if (hp_action == KEXEC_CRASH_HP_REMOVE_MEMORY ||
> hp_action == KEXEC_CRASH_HP_ADD_MEMORY) {
> - pr_info_once("Crash update is not supported for memory
> hotplug\n");
> - return;
> + struct memory_notify *mn;
> +
> + mn = (struct memory_notify *)arg;
> + update_crash_elfcorehdr(image, mn);
> }
> }
> #endif
> diff --git a/arch/powerpc/kexec/file_load_64.c
> b/arch/powerpc/kexec/file_load_64.c
> index e2148a009701..2457d7ec2075 100644
> --- a/arch/powerpc/kexec/file_load_64.c
> +++ b/arch/powerpc/kexec/file_load_64.c
> @@ -21,6 +21,8 @@
> #include <linux/memblock.h>
> #include <linux/slab.h>
> #include <linux/vmalloc.h>
> +#include <linux/elf.h>
> +
> #include <asm/setup.h>
> #include <asm/cputhreads.h>
> #include <asm/drmem.h>
> @@ -740,7 +742,35 @@ static int load_elfcorehdr_segment(struct kimage *image,
> struct kexec_buf *kbuf)
>
> kbuf->buffer = headers;
> kbuf->mem = KEXEC_BUF_MEM_UNKNOWN;
> - kbuf->bufsz = kbuf->memsz = headers_sz;
> + kbuf->bufsz = headers_sz;
> +#if defined(CONFIG_CRASH_HOTPLUG) && defined(CONFIG_MEMORY_HOTPLUG)
> + /* Adjust the elfcorehdr segment size to accommodate
> + * future crash memory ranges.
> + */
> + int max_lmb;
> + unsigned long pnum;
> +
> + /* In the worst case, a Phdr is needed for every other LMB to be
> + * represented as an individual crash range.
> + */
> + max_lmb = memory_hotplug_max() / (2 * drmem_lmb_size());
> +
> + /* Do not cross the Phdr max limit of the elf header.
> + * Avoid counting Phdr for crash ranges (cmem->nr_ranges)
> + * which are already part of elfcorehdr.
> + */
> + if (max_lmb > PN_XNUM)
> + pnum = PN_XNUM - cmem->nr_ranges;
> + else
> + pnum = max_lmb - cmem->nr_ranges;
> +
> + /* Additional buffer space for elfcorehdr to accommodate
> + * future memory ranges.
> + */
> + kbuf->memsz = headers_sz + pnum * sizeof(Elf64_Phdr);
> +#else
> + kbuf->memsz = headers_sz;
> +#endif
> kbuf->top_down = false;
>
> ret = kexec_add_buffer(kbuf);
> @@ -750,7 +780,7 @@ static int load_elfcorehdr_segment(struct kimage *image,
> struct kexec_buf *kbuf)
> }
>
> image->elf_load_addr = kbuf->mem;
> - image->elf_headers_sz = headers_sz;
> + image->elf_headers_sz = kbuf->memsz;
> image->elf_headers = headers;
> out:
> kfree(cmem);
> diff --git a/arch/powerpc/kexec/ranges.c b/arch/powerpc/kexec/ranges.c
> index fb3e12f15214..4fd0c5d5607b 100644
> --- a/arch/powerpc/kexec/ranges.c
> +++ b/arch/powerpc/kexec/ranges.c
> @@ -234,6 +234,91 @@ int add_mem_range(struct crash_mem **mem_ranges, u64
> base, u64 size)
> return __add_mem_range(mem_ranges, base, size);
> }
>
> +/**
> + * remove_mem_range - Removes the given memory range from the range list.
> + * @mem_ranges: Range list to remove the memory range to.
> + * @base: Base address of the range to remove.
> + * @size: Size of the memory range to remove.
> + *
> + * (Re)allocates memory, if needed.
> + *
> + * Returns 0 on success, negative errno on error.
> + */
> +int remove_mem_range(struct crash_mem **mem_ranges, u64 base, u64 size)
> +{
> + u64 end;
> + int ret = 0;
> + unsigned int i;
> + u64 mstart, mend;
> + struct crash_mem *mem_rngs = *mem_ranges;
> +
> + if (!size)
> + return 0;
> +
> + /*
> + * Memory range are stored as start and end address, use
> + * the same format to do remove operation.
> + */
> + end = base + size - 1;
> +
> + for (i = 0; i < mem_rngs->nr_ranges; i++) {
> + mstart = mem_rngs->ranges[i].start;
> + mend = mem_rngs->ranges[i].end;
> +
> + /*
> + * Memory range to remove is not part of this range entry
> + * in the memory range list
> + */
> + if (!(base >= mstart && end <= mend))
> + continue;
> +
> + /*
> + * Memory range to remove is equivalent to this entry in the
> + * memory range list. Remove the range entry from the list.
> + */
> + if (base == mstart && end == mend) {
> + for (; i < mem_rngs->nr_ranges - 1; i++) {
> + mem_rngs->ranges[i].start =
> mem_rngs->ranges[i+1].start;
> + mem_rngs->ranges[i].end =
> mem_rngs->ranges[i+1].end;
> + }
> + mem_rngs->nr_ranges--;
> + goto out;
> + }
> + /*
> + * Start address of the memory range to remove and the
> + * current memory range entry in the list is same. Just
> + * move the start address of the current memory range
> + * entry in the list to end + 1.
> + */
> + else if (base == mstart) {
> + mem_rngs->ranges[i].start = end + 1;
> + goto out;
> + }
> + /*
> + * End address of the memory range to remove and the
> + * current memory range entry in the list is same.
> + * Just move the end address of the current memory
> + * range entry in the list to base - 1.
> + */
> + else if (end == mend) {
> + mem_rngs->ranges[i].end = base - 1;
> + goto out;
> + }
> + /*
> + * Memory range to remove is not at the edge of current
> + * memory range entry. Split the current memory entry into
> + * two half.
> + */
> + else {
> + mem_rngs->ranges[i].end = base - 1;
> + size = mem_rngs->ranges[i].end - end;
> + ret = add_mem_range(mem_ranges, end + 1, size);
> + }
> + }
> +out:
> + return ret;
> +}
> +
> /**
> * add_tce_mem_ranges - Adds tce-table range to the given memory ranges list.
> * @mem_ranges: Range list to add the memory range(s) to.
> --
> 2.41.0
>
