Messages in this thread | | | Date | Mon, 9 Jan 2023 13:43:39 -0600 | Subject | Re: [PATCH v16 7/7] x86/crash: add x86 crash hotplug support | From | Eric DeVolder <> |
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On 1/9/23 01:36, Baoquan He wrote: > On 01/05/23 at 10:17am, Eric DeVolder wrote: > ...... >> @@ -394,10 +409,37 @@ 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; >> + >> + if (IS_ENABLED(CONFIG_CRASH_HOTPLUG)) { >> + /* >> + * 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; > > Logic of pnum calculating is a little confusing to me. If I only enable > one of CONFIG_HOTPLUG_CPU and CONFIG_MEMORY_HOTPLUG, is it OK? Say I > only enable CONFIG_HOTPLUG_CPU and CONFIG_SMP, on x86_64, > CONFIG_NR_CPUS_DEFAULT will be 64. pnum will be 64, is it OK. Am I miss > anything?
Ah, your understanding is correct, and the issue you point out I need to fix. Specifically is only one of HOTPLUG_CPU or MEMORY_HOTPLUG is set, then I need to allow a default for the other. Using the example you have above, there would not be room for a single memory region, so I need to allow for a default number of memory regions.
Good find! eric
> >> + >> + 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); >> + } >> + } >> >> - kbuf.memsz = kbuf.bufsz; >> kbuf.buf_align = ELF_CORE_HEADER_ALIGN; >> kbuf.mem = KEXEC_BUF_MEM_UNKNOWN; >> ret = kexec_add_buffer(&kbuf); >> @@ -412,3 +454,67 @@ int crash_load_segments(struct kimage *image) >> return ret; >> } >> #endif /* CONFIG_KEXEC_FILE */ >
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