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x86/crash: add x86 crash hotplug support
When CPU or memory is hot un/plugged, or off/onlined, the crash elfcorehdr, which describes the CPUs and memory in the system, must also be updated. A new elfcorehdr is generated from the available CPUs and memory and replaces the existing elfcorehdr. The segment containing the elfcorehdr is identified at run-time in crash_core:crash_handle_hotplug_event(). No modifications to purgatory (see 'kexec: exclude elfcorehdr from the segment digest') or boot_params (as the elfcorehdr= capture kernel command line parameter pointer remains unchanged and correct) are needed, just elfcorehdr. For kexec_file_load(), the elfcorehdr segment size is based on NR_CPUS and CRASH_MAX_MEMORY_RANGES in order to accommodate a growing number of CPU and memory resources. For kexec_load(), the userspace kexec utility needs to size the elfcorehdr segment in the same/similar manner. To accommodate kexec_load() syscall in the absence of kexec_file_load() syscall support, prepare_elf_headers() and dependents are moved outside of CONFIG_KEXEC_FILE. [eric.devolder@oracle.com: correct unused function build error] Link: https://lkml.kernel.org/r/20230821182644.2143-1-eric.devolder@oracle.com Link: https://lkml.kernel.org/r/20230814214446.6659-6-eric.devolder@oracle.com Signed-off-by: Eric DeVolder <eric.devolder@oracle.com> Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com> Acked-by: Hari Bathini <hbathini@linux.ibm.com> Acked-by: Baoquan He <bhe@redhat.com> Cc: Akhil Raj <lf32.dev@gmail.com> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: Borislav Petkov (AMD) <bp@alien8.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Dave Young <dyoung@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Mimi Zohar <zohar@linux.ibm.com> Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: "Rafael J. Wysocki" <rafael@kernel.org> Cc: Sean Christopherson <seanjc@google.com> Cc: Takashi Iwai <tiwai@suse.de> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Thomas Weißschuh <linux@weissschuh.net> Cc: Valentin Schneider <vschneid@redhat.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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@ -2069,6 +2069,9 @@ config ARCH_SUPPORTS_KEXEC_JUMP
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config ARCH_SUPPORTS_CRASH_DUMP
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def_bool X86_64 || (X86_32 && HIGHMEM)
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config ARCH_SUPPORTS_CRASH_HOTPLUG
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def_bool y
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config PHYSICAL_START
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hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
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default "0x1000000"
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@ -209,6 +209,21 @@ typedef void crash_vmclear_fn(void);
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extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss;
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extern void kdump_nmi_shootdown_cpus(void);
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#ifdef CONFIG_CRASH_HOTPLUG
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void arch_crash_handle_hotplug_event(struct kimage *image);
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#define arch_crash_handle_hotplug_event arch_crash_handle_hotplug_event
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#ifdef CONFIG_HOTPLUG_CPU
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static inline int crash_hotplug_cpu_support(void) { return 1; }
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#define crash_hotplug_cpu_support crash_hotplug_cpu_support
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#endif
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#ifdef CONFIG_MEMORY_HOTPLUG
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static inline int crash_hotplug_memory_support(void) { return 1; }
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#define crash_hotplug_memory_support crash_hotplug_memory_support
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#endif
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#endif
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#endif /* __ASSEMBLY__ */
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#endif /* _ASM_X86_KEXEC_H */
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@ -158,8 +158,7 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
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crash_save_cpu(regs, safe_smp_processor_id());
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}
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#ifdef CONFIG_KEXEC_FILE
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#if defined(CONFIG_KEXEC_FILE) || defined(CONFIG_CRASH_HOTPLUG)
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static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
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{
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unsigned int *nr_ranges = arg;
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@ -231,7 +230,7 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
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/* Prepare elf headers. Return addr and size */
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static int prepare_elf_headers(struct kimage *image, void **addr,
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unsigned long *sz)
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unsigned long *sz, unsigned long *nr_mem_ranges)
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{
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struct crash_mem *cmem;
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int ret;
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@ -249,6 +248,9 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
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if (ret)
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goto out;
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/* Return the computed number of memory ranges, for hotplug usage */
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*nr_mem_ranges = cmem->nr_ranges;
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/* By default prepare 64bit headers */
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ret = crash_prepare_elf64_headers(cmem, IS_ENABLED(CONFIG_X86_64), addr, sz);
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@ -256,7 +258,9 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
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vfree(cmem);
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return ret;
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}
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#endif
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#ifdef CONFIG_KEXEC_FILE
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static int add_e820_entry(struct boot_params *params, struct e820_entry *entry)
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{
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unsigned int nr_e820_entries;
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@ -371,18 +375,42 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
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int crash_load_segments(struct kimage *image)
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{
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int ret;
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unsigned long pnum = 0;
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struct kexec_buf kbuf = { .image = image, .buf_min = 0,
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.buf_max = ULONG_MAX, .top_down = false };
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/* Prepare elf headers and add a segment */
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ret = prepare_elf_headers(image, &kbuf.buffer, &kbuf.bufsz);
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ret = prepare_elf_headers(image, &kbuf.buffer, &kbuf.bufsz, &pnum);
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if (ret)
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return ret;
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image->elf_headers = kbuf.buffer;
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image->elf_headers_sz = kbuf.bufsz;
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kbuf.memsz = kbuf.bufsz;
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#ifdef CONFIG_CRASH_HOTPLUG
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/*
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* The elfcorehdr segment size accounts for VMCOREINFO, kernel_map,
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* maximum CPUs and maximum memory ranges.
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*/
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if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
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pnum = 2 + CONFIG_NR_CPUS_DEFAULT + CONFIG_CRASH_MAX_MEMORY_RANGES;
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else
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pnum += 2 + CONFIG_NR_CPUS_DEFAULT;
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if (pnum < (unsigned long)PN_XNUM) {
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kbuf.memsz = pnum * sizeof(Elf64_Phdr);
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kbuf.memsz += sizeof(Elf64_Ehdr);
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image->elfcorehdr_index = image->nr_segments;
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/* Mark as usable to crash kernel, else crash kernel fails on boot */
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image->elf_headers_sz = kbuf.memsz;
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} else {
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pr_err("number of Phdrs %lu exceeds max\n", pnum);
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}
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#endif
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kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
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kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
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ret = kexec_add_buffer(&kbuf);
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@ -395,3 +423,66 @@ int crash_load_segments(struct kimage *image)
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return ret;
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}
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#endif /* CONFIG_KEXEC_FILE */
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#ifdef CONFIG_CRASH_HOTPLUG
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#undef pr_fmt
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#define pr_fmt(fmt) "crash hp: " fmt
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/**
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* arch_crash_handle_hotplug_event() - Handle hotplug elfcorehdr changes
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* @image: a pointer to kexec_crash_image
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*
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* Prepare the new elfcorehdr and replace the existing elfcorehdr.
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*/
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void arch_crash_handle_hotplug_event(struct kimage *image)
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{
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void *elfbuf = NULL, *old_elfcorehdr;
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unsigned long nr_mem_ranges;
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unsigned long mem, memsz;
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unsigned long elfsz = 0;
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/*
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* Create the new elfcorehdr reflecting the changes to CPU and/or
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* memory resources.
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*/
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if (prepare_elf_headers(image, &elfbuf, &elfsz, &nr_mem_ranges)) {
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pr_err("unable to create new elfcorehdr");
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goto out;
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}
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/*
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* Obtain address and size of the elfcorehdr segment, and
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* check it against the new elfcorehdr buffer.
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*/
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mem = image->segment[image->elfcorehdr_index].mem;
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memsz = image->segment[image->elfcorehdr_index].memsz;
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if (elfsz > memsz) {
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pr_err("update elfcorehdr elfsz %lu > memsz %lu",
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elfsz, memsz);
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goto out;
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}
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/*
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* Copy new elfcorehdr over the old elfcorehdr at destination.
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*/
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old_elfcorehdr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
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if (!old_elfcorehdr) {
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pr_err("mapping elfcorehdr segment failed\n");
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goto out;
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}
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/*
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* Temporarily invalidate the crash image while the
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* elfcorehdr is updated.
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*/
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xchg(&kexec_crash_image, NULL);
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memcpy_flushcache(old_elfcorehdr, elfbuf, elfsz);
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xchg(&kexec_crash_image, image);
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kunmap_local(old_elfcorehdr);
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pr_debug("updated elfcorehdr\n");
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out:
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vfree(elfbuf);
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}
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#endif
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