Re: [PATCH v14 6/6] powerpc: add crash memory hotplug support
From: Baoquan He <bhe@redhat.com>
Date: 2023-12-15 01:24:33
Also in:
kexec
On 12/11/23 at 02:00pm, Sourabh Jain wrote: ......
quoted hunk ↗ jump to hunk
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_MMUdiff --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.
quoted hunk ↗ jump to hunk
+ 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); } } #endifdiff --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