On 12/09/22 at 10:36am, Eric DeVolder wrote: ...... snip out > diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c > index 9ceb93c176a6..5186df48ce6c 100644 > --- a/arch/x86/kernel/crash.c > +++ b/arch/x86/kernel/crash.c > @@ -42,6 +42,21 @@ > #include <asm/crash.h> > #include <asm/cmdline.h> > > +/* > + * For the kexec_file_load() syscall path, specify the maximum number of > + * memory regions that the elfcorehdr buffer/segment can accommodate. > + * These regions are obtained via walk_system_ram_res(); eg. the > + * 'System RAM' entries in /proc/iomem. > + * This value is combined with NR_CPUS_DEFAULT and multiplied by > + * sizeof(Elf64_Phdr) to determine the final elfcorehdr memory buffer/ > + * segment size. > + * The value 8192, for example, covers a (sparsely populated) 1TiB system > + * consisting of 128MiB memblocks, while resulting in an elfcorehdr > + * memory buffer/segment size under 1MiB. This represents a sane choice > + * to accommodate both baremetal and virtual machine configurations. > + */ > +#define CRASH_MAX_MEMORY_RANGES 8192 > + > /* Used while preparing memory map entries for second kernel */ > struct crash_memmap_data { > struct boot_params *params; > @@ -394,10 +409,39 @@ int crash_load_segments(struct kimage *image) > if (ret) > return ret; > > - image->elf_headers = kbuf.buffer; > - image->elf_headers_sz = kbuf.bufsz; > + image->elf_headers = kbuf.buffer; > + image->elf_headers_sz = kbuf.bufsz; > + kbuf.memsz = kbuf.bufsz; > + > +#ifdef CONFIG_CRASH_HOTPLUG > + if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) { Do I miss anything important during reviewing? I can't see why memory hotplug is also relying on HOTPLUG_CPU. > + /* > + * Ensure the elfcorehdr segment large enough for hotplug changes. > + * Start with VMCOREINFO and kernel_map. > + */ > + unsigned long pnum = 2; > + > + if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) > + pnum += CONFIG_NR_CPUS_DEFAULT; > + > + if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) > + pnum += CRASH_MAX_MEMORY_RANGES; > + > + if (pnum < (unsigned long)PN_XNUM) { > + kbuf.memsz = pnum * sizeof(Elf64_Phdr); > + kbuf.memsz += sizeof(Elf64_Ehdr); > + > + image->elfcorehdr_index = image->nr_segments; > + image->elfcorehdr_index_valid = true; > + > + /* Mark as usable to crash kernel, else crash kernel fails on boot */ > + image->elf_headers_sz = kbuf.memsz; > + } else { > + pr_err("number of Phdrs %lu exceeds max\n", pnum); > + } > + } > +#endif > > - kbuf.memsz = kbuf.bufsz; > kbuf.buf_align = ELF_CORE_HEADER_ALIGN; > kbuf.mem = KEXEC_BUF_MEM_UNKNOWN; > ret = kexec_add_buffer(&kbuf); > @@ -412,3 +456,67 @@ int crash_load_segments(struct kimage *image) > return ret; > } > #endif /* CONFIG_KEXEC_FILE */ > + > +#ifdef CONFIG_CRASH_HOTPLUG > + > +#undef pr_fmt > +#define pr_fmt(fmt) "crash hp: " fmt > + > +/** > + * arch_crash_handle_hotplug_event() - Handle hotplug elfcorehdr changes > + * @image: the active struct kimage > + * > + * 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) > +{ > + void *elfbuf = NULL, *old_elfcorehdr; > + unsigned long mem, memsz; > + unsigned long elfsz = 0; > + > + /* > + * Create the new elfcorehdr reflecting the changes to CPU and/or > + * memory resources. > + */ > + if (prepare_elf_headers(image, &elfbuf, &elfsz)) { > + pr_err("unable to prepare elfcore headers"); > + goto out; > + } > + > + /* > + * Obtain address and size of the elfcorehdr segment, and > + * check it against the new elfcorehdr buffer. > + */ > + mem = image->segment[image->elfcorehdr_index].mem; > + memsz = image->segment[image->elfcorehdr_index].memsz; > + if (elfsz > memsz) { > + pr_err("update elfcorehdr elfsz %lu > memsz %lu", > + elfsz, memsz); > + goto out; > + } > + > + /* > + * Copy new elfcorehdr over the old elfcorehdr at destination. > + */ > + old_elfcorehdr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT)); > + if (old_elfcorehdr) { > + pr_err("updating elfcorehdr failed\n"); > + goto out; > + } > + > + /* > + * Temporarily invalidate the crash image while the > + * elfcorehdr is updated. > + */ > + xchg(&kexec_crash_image, NULL); > + memcpy_flushcache(old_elfcorehdr, elfbuf, elfsz); > + xchg(&kexec_crash_image, image); > + kunmap_local(old_elfcorehdr); > + pr_debug("updated elfcorehdr\n"); > + > +out: > + vfree(elfbuf); > +} > +#endif > -- > 2.31.1 > _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec