On 07/07/22 at 07:55am, Eric DeVolder wrote: > > > On 6/20/22 00:06, Sourabh Jain wrote: > > Hello Eric, > > > > On 14/06/22 04:12, 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/kernel/crash.c | 116 ++++++++++++++++++++++++++++++++++++++++ > > > 2 files changed, 127 insertions(+) > > > > > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > > > index 762a0b6ab8b6..e9eecff3b97d 100644 > > > --- a/arch/x86/Kconfig > > > +++ b/arch/x86/Kconfig > > > @@ -2082,6 +2082,17 @@ 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/kernel/crash.c b/arch/x86/kernel/crash.c > > > index 9db41cce8d97..b9cdf7a0d868 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> > > > @@ -398,7 +399,17 @@ 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); > > > + /* For marking as usable to crash kernel */ > > > + image->elf_headers_sz = kbuf.memsz; > > > + /* Record the index of the elfcorehdr segment */ > > > + 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); > > > @@ -413,3 +424,108 @@ int crash_load_segments(struct kimage *image) > > > return ret; > > > } > > > #endif /* CONFIG_KEXEC_FILE */ > > > + > > > +#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG) > > > +int crash_hotplug_support(void) { return 1; } > > > +void *arch_map_crash_pages(unsigned long paddr, unsigned long size) > > > +{ > > > + /* > > > + * 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 *ptr = NULL; > > > + > > > + /* NOTE: requires arch_kexec_[un]protect_crashkres() for write access */ > > > + if (size > 0) { > > > + struct page *page = pfn_to_page(paddr >> PAGE_SHIFT); > > > + > > > + ptr = kmap(page); > > > + } > > > + > > > + return ptr; > > > +} > > > + > > > +void arch_unmap_crash_pages(void **ptr) > > > +{ > > > + if (ptr) { > > > + if (*ptr) > > > + kunmap(*ptr); > > > + *ptr = NULL; > > > + } > > > +} > > > > Aren't arch will have build issue if arch_[un]map_crash_pages methods are not defined? > Sourabh, > Yes, you are correct. I'll add __weak versions of each in crash_core.c in the next patch. Just a reminder, __weak is deprecated and has been cleaned up in kernel/kexec*.c in below patch. [PATCH 0/2] kexec: Drop __weak attributes from functions _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec