From: Eric DeVolder <eric.devolder@oracle.com> To: linux-kernel@vger.kernel.org, x86@kernel.org, kexec@lists.infradead.org, ebiederm@xmission.com, dyoung@redhat.com, bhe@redhat.com, vgoyal@redhat.com Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, nramas@linux.microsoft.com, thomas.lendacky@amd.com, robh@kernel.org, efault@gmx.de, rppt@kernel.org, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com, eric.devolder@oracle.com Subject: [PATCH v4 09/10] crash hp: Add x86 crash hotplug support for kexec_file_load Date: Wed, 9 Feb 2022 14:57:05 -0500 [thread overview] Message-ID: <20220209195706.51522-10-eric.devolder@oracle.com> (raw) In-Reply-To: <20220209195706.51522-1-eric.devolder@oracle.com> 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. 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 if no errors occur, it is installed over the top of the existing elfcorehdr. In the patch 'crash hp: 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_HOTPLUG_ELFCOREHDR_SZ configure item. With this change, the kexec_file_load syscall (not kexec_load) is supported. When loading the crash kernel via kexec_file_load, the elfcorehdr is identified at load time in crash_load_segments(). Signed-off-by: Eric DeVolder <eric.devolder@oracle.com> --- arch/x86/kernel/crash.c | 92 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 92 insertions(+) diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c index 9db41cce8d97..6215c51919db 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; +#ifdef CONFIG_CRASH_HOTPLUG + /* Ensure elfcorehdr segment large enough for hotplug changes */ + kbuf.memsz = CONFIG_CRASH_HOTPLUG_ELFCOREHDR_SZ; + /* For marking as usable to crash kernel */ + image->elf_headers_sz = kbuf.memsz; + /* Record the index of the elfcorehdr segment */ + image->elf_index = image->nr_segments; + image->elf_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 +424,84 @@ int crash_load_segments(struct kimage *image) return ret; } #endif /* CONFIG_KEXEC_FILE */ + +#ifdef CONFIG_CRASH_HOTPLUG +/** + * arch_crash_hotplug_handler() - Handle hotplug elfcorehdr changes + * @image: the active struct kimage + * @hp_action: the hot un/plug action being handled + * @a: first parameter dependent upon hp_action + * @b: first parameter dependent upon hp_action + * + * To accurately reflect hot un/plug changes, the elfcorehdr (which + * is passed to the crash kernel via the elfcorehdr= parameter) + * must be updated with the new list of CPUs and memories. The new + * elfcorehdr is prepared in a kernel buffer, and if no errors, + * then it is written on top of the existing/old elfcorehdr. + * + * For hotplug changes to elfcorehdr to work, two conditions are + * needed: + * First, the segment containing the elfcorehdr must be large enough + * to permit a growing number of resources. See + * CONFIG_CRASH_HOTPLUG_ELFCOREHDR_SZ. + * Second, purgatory must explicitly exclude the elfcorehdr from the + * list of segments it checks (since the elfcorehdr changes and thus + * would require an update to purgatory itself to update the digest). + * + */ +void arch_crash_hotplug_handler(struct kimage *image, + unsigned int hp_action, unsigned long a, unsigned long b) +{ + struct kexec_segment *ksegment; + unsigned char *ptr = NULL; + unsigned long elfsz = 0; + void *elfbuf = NULL; + unsigned long mem, memsz; + + /* Must have valid elfcorehdr index */ + if (!image->elf_index_valid) { + pr_err("crash hp: unable to locate elfcorehdr segment"); + goto out; + } + + ksegment = &image->segment[image->elf_index]; + mem = ksegment->mem; + memsz = ksegment->memsz; + + /* + * Create the new elfcorehdr reflecting the changes to CPU and/or + * memory resources. The elfcorehdr segment memsz must be + * sufficiently large to accommodate increases due to hotplug + * activity. See CRASH_HOTPLUG_ELFCOREHDR_SZ. + */ + 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 = map_crash_pages(mem, memsz); + if (ptr) { + /* Temporarily invalidate the crash image while it is replaced */ + xchg(&kexec_crash_image, NULL); + /* Write the new elfcorehdr into memory */ + memcpy_flushcache((void *)ptr, elfbuf, elfsz); + /* The crash image is now valid once again */ + xchg(&kexec_crash_image, image); + } + unmap_crash_pages((void **)&ptr); + pr_debug("crash hp: re-loaded elfcorehdr at 0x%lx\n", mem); + +out: + if (elfbuf) + vfree(elfbuf); +} +#endif /* CONFIG_CRASH_HOTPLUG */ -- 2.27.0
WARNING: multiple messages have this Message-ID (diff)
From: Eric DeVolder <eric.devolder@oracle.com> To: kexec@lists.infradead.org Subject: [PATCH v4 09/10] crash hp: Add x86 crash hotplug support for kexec_file_load Date: Wed, 9 Feb 2022 14:57:05 -0500 [thread overview] Message-ID: <20220209195706.51522-10-eric.devolder@oracle.com> (raw) In-Reply-To: <20220209195706.51522-1-eric.devolder@oracle.com> 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. 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 if no errors occur, it is installed over the top of the existing elfcorehdr. In the patch 'crash hp: 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_HOTPLUG_ELFCOREHDR_SZ configure item. With this change, the kexec_file_load syscall (not kexec_load) is supported. When loading the crash kernel via kexec_file_load, the elfcorehdr is identified at load time in crash_load_segments(). Signed-off-by: Eric DeVolder <eric.devolder@oracle.com> --- arch/x86/kernel/crash.c | 92 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 92 insertions(+) diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c index 9db41cce8d97..6215c51919db 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; +#ifdef CONFIG_CRASH_HOTPLUG + /* Ensure elfcorehdr segment large enough for hotplug changes */ + kbuf.memsz = CONFIG_CRASH_HOTPLUG_ELFCOREHDR_SZ; + /* For marking as usable to crash kernel */ + image->elf_headers_sz = kbuf.memsz; + /* Record the index of the elfcorehdr segment */ + image->elf_index = image->nr_segments; + image->elf_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 +424,84 @@ int crash_load_segments(struct kimage *image) return ret; } #endif /* CONFIG_KEXEC_FILE */ + +#ifdef CONFIG_CRASH_HOTPLUG +/** + * arch_crash_hotplug_handler() - Handle hotplug elfcorehdr changes + * @image: the active struct kimage + * @hp_action: the hot un/plug action being handled + * @a: first parameter dependent upon hp_action + * @b: first parameter dependent upon hp_action + * + * To accurately reflect hot un/plug changes, the elfcorehdr (which + * is passed to the crash kernel via the elfcorehdr= parameter) + * must be updated with the new list of CPUs and memories. The new + * elfcorehdr is prepared in a kernel buffer, and if no errors, + * then it is written on top of the existing/old elfcorehdr. + * + * For hotplug changes to elfcorehdr to work, two conditions are + * needed: + * First, the segment containing the elfcorehdr must be large enough + * to permit a growing number of resources. See + * CONFIG_CRASH_HOTPLUG_ELFCOREHDR_SZ. + * Second, purgatory must explicitly exclude the elfcorehdr from the + * list of segments it checks (since the elfcorehdr changes and thus + * would require an update to purgatory itself to update the digest). + * + */ +void arch_crash_hotplug_handler(struct kimage *image, + unsigned int hp_action, unsigned long a, unsigned long b) +{ + struct kexec_segment *ksegment; + unsigned char *ptr = NULL; + unsigned long elfsz = 0; + void *elfbuf = NULL; + unsigned long mem, memsz; + + /* Must have valid elfcorehdr index */ + if (!image->elf_index_valid) { + pr_err("crash hp: unable to locate elfcorehdr segment"); + goto out; + } + + ksegment = &image->segment[image->elf_index]; + mem = ksegment->mem; + memsz = ksegment->memsz; + + /* + * Create the new elfcorehdr reflecting the changes to CPU and/or + * memory resources. The elfcorehdr segment memsz must be + * sufficiently large to accommodate increases due to hotplug + * activity. See CRASH_HOTPLUG_ELFCOREHDR_SZ. + */ + 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 = map_crash_pages(mem, memsz); + if (ptr) { + /* Temporarily invalidate the crash image while it is replaced */ + xchg(&kexec_crash_image, NULL); + /* Write the new elfcorehdr into memory */ + memcpy_flushcache((void *)ptr, elfbuf, elfsz); + /* The crash image is now valid once again */ + xchg(&kexec_crash_image, image); + } + unmap_crash_pages((void **)&ptr); + pr_debug("crash hp: re-loaded elfcorehdr at 0x%lx\n", mem); + +out: + if (elfbuf) + vfree(elfbuf); +} +#endif /* CONFIG_CRASH_HOTPLUG */ -- 2.27.0
next prev parent reply other threads:[~2022-02-09 20:03 UTC|newest] Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-02-09 19:56 [PATCH v4 00/10] crash: Kernel handling of CPU and memory hot un/plug Eric DeVolder 2022-02-09 19:56 ` Eric DeVolder 2022-02-09 19:56 ` [PATCH v4 01/10] crash: fix minor typo/bug in debug message Eric DeVolder 2022-02-09 19:56 ` Eric DeVolder 2022-02-09 19:56 ` [PATCH v4 02/10] crash hp: Introduce CRASH_HOTPLUG configuration options Eric DeVolder 2022-02-09 19:56 ` Eric DeVolder 2022-02-23 3:25 ` Baoquan He 2022-02-23 3:25 ` Baoquan He 2022-03-01 20:04 ` Eric DeVolder 2022-03-01 20:04 ` Eric DeVolder 2022-03-02 9:20 ` David Hildenbrand 2022-03-02 9:20 ` David Hildenbrand 2022-03-03 10:22 ` Baoquan He 2022-03-03 10:22 ` Baoquan He 2022-03-03 11:36 ` David Hildenbrand 2022-03-03 11:36 ` David Hildenbrand 2022-03-03 12:08 ` Baoquan He 2022-03-03 12:08 ` Baoquan He 2022-03-03 15:31 ` Eric DeVolder 2022-03-03 15:31 ` Eric DeVolder 2022-02-09 19:56 ` [PATCH v4 03/10] crash hp: definitions and prototype changes Eric DeVolder 2022-02-09 19:56 ` Eric DeVolder 2022-02-23 3:43 ` Baoquan He 2022-02-23 3:43 ` Baoquan He 2022-03-01 20:04 ` Eric DeVolder 2022-03-01 20:04 ` Eric DeVolder 2022-02-09 19:57 ` [PATCH v4 04/10] crash hp: prototype change for crash_prepare_elf64_headers Eric DeVolder 2022-02-09 19:57 ` Eric DeVolder 2022-02-23 3:46 ` Baoquan He 2022-02-23 3:46 ` Baoquan He 2022-03-01 20:05 ` Eric DeVolder 2022-03-01 20:05 ` Eric DeVolder 2022-02-09 19:57 ` [PATCH v4 05/10] crash hp: introduce helper functions un/map_crash_pages Eric DeVolder 2022-02-09 19:57 ` Eric DeVolder 2022-02-23 3:58 ` Baoquan He 2022-02-23 3:58 ` Baoquan He 2022-03-01 20:06 ` Eric DeVolder 2022-03-01 20:06 ` Eric DeVolder 2022-02-09 19:57 ` [PATCH v4 06/10] crash hp: generic crash hotplug support infrastructure Eric DeVolder 2022-02-09 19:57 ` Eric DeVolder 2022-02-23 3:59 ` Baoquan He 2022-02-23 3:59 ` Baoquan He 2022-03-01 20:07 ` Eric DeVolder 2022-03-01 20:07 ` Eric DeVolder 2022-02-09 19:57 ` [PATCH v4 07/10] crash hp: exclude elfcorehdr from the segment digest Eric DeVolder 2022-02-09 19:57 ` Eric DeVolder 2022-02-23 4:00 ` Baoquan He 2022-02-23 4:00 ` Baoquan He 2022-03-01 20:07 ` Eric DeVolder 2022-03-01 20:07 ` Eric DeVolder 2022-02-09 19:57 ` [PATCH v4 08/10] crash hp: exclude hot remove cpu from elfcorehdr notes Eric DeVolder 2022-02-09 19:57 ` Eric DeVolder 2022-02-23 4:04 ` Baoquan He 2022-02-23 4:04 ` Baoquan He 2022-03-01 20:08 ` Eric DeVolder 2022-03-01 20:08 ` Eric DeVolder 2022-02-09 19:57 ` Eric DeVolder [this message] 2022-02-09 19:57 ` [PATCH v4 09/10] crash hp: Add x86 crash hotplug support for kexec_file_load Eric DeVolder 2022-02-23 4:10 ` Baoquan He 2022-02-23 4:10 ` Baoquan He 2022-03-01 20:12 ` Eric DeVolder 2022-03-01 20:12 ` Eric DeVolder 2022-03-03 10:27 ` Baoquan He 2022-03-03 10:27 ` Baoquan He 2022-02-09 19:57 ` [PATCH v4 10/10] crash hp: Add x86 crash hotplug support for kexec_load Eric DeVolder 2022-02-09 19:57 ` Eric DeVolder 2022-02-21 4:08 ` [PATCH v4 00/10] crash: Kernel handling of CPU and memory hot un/plug Baoquan He 2022-02-21 4:08 ` Baoquan He
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