On 08/26/22 at 01:37pm, Eric DeVolder wrote: > For x86_64, when CPU or memory is hot un/plugged, the crash > elfcorehdr, which describes the CPUs and memory in the system, > must also be updated. > > When loading the crash kernel via kexec_load or kexec_file_load, > the elfcorehdr is identified at run time in > crash_core:handle_hotplug_event(). > > To update the elfcorehdr for x86_64, a new elfcorehdr must be > generated from the available CPUs and memory. The new elfcorehdr > is prepared into a buffer, and then installed over the top of > the existing elfcorehdr. > > In the patch 'kexec: exclude elfcorehdr from the segment digest' > the need to update purgatory due to the change in elfcorehdr was > eliminated. As a result, no changes to purgatory or boot_params > (as the elfcorehdr= kernel command line parameter pointer > remains unchanged and correct) are needed, just elfcorehdr. > > To accommodate a growing number of resources via hotplug, the > elfcorehdr segment must be sufficiently large enough to accommodate > changes, see the CRASH_MAX_MEMORY_RANGES configure item. > > With this change, crash hotplug for kexec_file_load syscall > is supported. The kexec_load is also supported, but also > requires a corresponding change to userspace kexec-tools. > > Signed-off-by: Eric DeVolder <eric.devolder@xxxxxxxxxx> > --- > arch/x86/Kconfig | 11 ++++ > arch/x86/include/asm/kexec.h | 20 +++++++ > arch/x86/kernel/crash.c | 102 +++++++++++++++++++++++++++++++++++ > 3 files changed, 133 insertions(+) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index f9920f1341c8..cdfc9b2fdf98 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -2056,6 +2056,17 @@ config CRASH_DUMP > (CONFIG_RELOCATABLE=y). > For more details see Documentation/admin-guide/kdump/kdump.rst > > +config CRASH_MAX_MEMORY_RANGES > + depends on CRASH_DUMP && KEXEC_FILE && (HOTPLUG_CPU || MEMORY_HOTPLUG) > + int > + default 32768 > + help > + For the kexec_file_load path, specify the maximum number of > + memory regions, eg. as represented by the 'System RAM' entries > + in /proc/iomem, that the elfcorehdr buffer/segment can accommodate. > + This value is combined with NR_CPUS and multiplied by Elf64_Phdr > + size to determine the final buffer size. > + > config KEXEC_JUMP > bool "kexec jump" > depends on KEXEC && HIBERNATION > diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h > index a3760ca796aa..432073385b2d 100644 > --- a/arch/x86/include/asm/kexec.h > +++ b/arch/x86/include/asm/kexec.h > @@ -212,6 +212,26 @@ typedef void crash_vmclear_fn(void); > extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss; > extern void kdump_nmi_shootdown_cpus(void); > > +void *arch_map_crash_pages(unsigned long paddr, unsigned long size); > +#define arch_map_crash_pages arch_map_crash_pages > + > +void arch_unmap_crash_pages(void **ptr); > +#define arch_unmap_crash_pages arch_unmap_crash_pages > + > +void arch_crash_handle_hotplug_event(struct kimage *image, > + unsigned int hp_action); > +#define arch_crash_handle_hotplug_event arch_crash_handle_hotplug_event > + > +#ifdef CONFIG_HOTPLUG_CPU > +static inline int crash_hotplug_cpu_support(void) { return 1; } > +#define crash_hotplug_cpu_support crash_hotplug_cpu_support > +#endif > + > +#ifdef CONFIG_MEMORY_HOTPLUG > +static inline int crash_hotplug_memory_support(void) { return 1; } > +#define crash_hotplug_memory_support crash_hotplug_memory_support > +#endif Check these two functions again, wonder whether this is a common usage to show support of a feature. I don't remember where we do like this. We usually define a global variable to mark it? Anyway, it works. See if other people have comments, I could be ignorant. Other than this tiny concern, this patch looks good to me: Acked-by: Baoquan He <bhe@xxxxxxxxxx> > + > #endif /* __ASSEMBLY__ */ > > #endif /* _ASM_X86_KEXEC_H */ > diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c > index 9ceb93c176a6..8fc7d678ac72 100644 > --- a/arch/x86/kernel/crash.c > +++ b/arch/x86/kernel/crash.c > @@ -25,6 +25,7 @@ > #include <linux/slab.h> > #include <linux/vmalloc.h> > #include <linux/memblock.h> > +#include <linux/highmem.h> > > #include <asm/processor.h> > #include <asm/hardirq.h> > @@ -397,7 +398,18 @@ int crash_load_segments(struct kimage *image) > image->elf_headers = kbuf.buffer; > image->elf_headers_sz = kbuf.bufsz; > > +#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG) > + /* Ensure elfcorehdr segment large enough for hotplug changes */ > + kbuf.memsz = > + (CONFIG_NR_CPUS_DEFAULT + CONFIG_CRASH_MAX_MEMORY_RANGES) * > + sizeof(Elf64_Phdr); > + /* Mark as usable to crash kernel, else crash kernel fails on boot */ > + image->elf_headers_sz = kbuf.memsz; > + image->elfcorehdr_index = image->nr_segments; > + image->elfcorehdr_index_valid = true; > +#else > kbuf.memsz = kbuf.bufsz; > +#endif > kbuf.buf_align = ELF_CORE_HEADER_ALIGN; > kbuf.mem = KEXEC_BUF_MEM_UNKNOWN; > ret = kexec_add_buffer(&kbuf); > @@ -412,3 +424,93 @@ int crash_load_segments(struct kimage *image) > return ret; > } > #endif /* CONFIG_KEXEC_FILE */ > + > +#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG) > +/* > + * NOTE: The addresses and sizes passed to this routine have > + * already been fully aligned on page boundaries. There is no > + * need for massaging the address or size. > + */ > +void *arch_map_crash_pages(unsigned long paddr, unsigned long size) > +{ > + void *ptr = NULL; > + > + if (size > 0) { > + struct page *page = pfn_to_page(paddr >> PAGE_SHIFT); > + > + ptr = kmap_local_page(page); > + } > + > + return ptr; > +} > + > +void arch_unmap_crash_pages(void **ptr) > +{ > + if (ptr) { > + if (*ptr) > + kunmap_local(*ptr); > + *ptr = NULL; > + } > +} > + > +/** > + * arch_crash_handle_hotplug_event() - Handle hotplug elfcorehdr changes > + * @image: the active struct kimage > + * @hp_action: the hot un/plug action being handled > + * > + * To accurately reflect hot un/plug changes, the new elfcorehdr > + * is prepared in a kernel buffer, and then it is written on top > + * of the existing/old elfcorehdr. > + */ > +void arch_crash_handle_hotplug_event(struct kimage *image, > + unsigned int hp_action) > +{ > + struct kexec_segment *ksegment; > + unsigned char *ptr = NULL; > + unsigned long elfsz = 0; > + void *elfbuf = NULL; > + unsigned long mem, memsz; > + > + /* > + * Elfcorehdr_index_valid checked in crash_core:handle_hotplug_event() > + */ > + ksegment = &image->segment[image->elfcorehdr_index]; > + mem = ksegment->mem; > + memsz = ksegment->memsz; > + > + /* > + * Create the new elfcorehdr reflecting the changes to CPU and/or > + * memory resources. > + */ > + if (prepare_elf_headers(image, &elfbuf, &elfsz)) { > + pr_err("crash hp: unable to prepare elfcore headers"); > + goto out; > + } > + if (elfsz > memsz) { > + pr_err("crash hp: update elfcorehdr elfsz %lu > memsz %lu", > + elfsz, memsz); > + goto out; > + } > + > + /* > + * At this point, we are all but assured of success. > + * Copy new elfcorehdr into destination. > + */ > + ptr = arch_map_crash_pages(mem, memsz); > + if (ptr) { > + /* > + * Temporarily invalidate the crash image while the > + * elfcorehdr is updated. > + */ > + xchg(&kexec_crash_image, NULL); > + memcpy_flushcache((void *)ptr, elfbuf, elfsz); > + xchg(&kexec_crash_image, image); > + } > + arch_unmap_crash_pages((void **)&ptr); > + pr_debug("crash hp: re-loaded elfcorehdr at 0x%lx\n", mem); > + > +out: > + if (elfbuf) > + vfree(elfbuf); > +} > +#endif > -- > 2.31.1 > _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec