From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EF0D9ECAAD5 for ; Mon, 5 Sep 2022 03:19:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235951AbiIEDTV (ORCPT ); Sun, 4 Sep 2022 23:19:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37096 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234382AbiIEDTQ (ORCPT ); Sun, 4 Sep 2022 23:19:16 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 27A0C2CCB7 for ; Sun, 4 Sep 2022 20:19:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1662347954; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=yJDDIimosi3B8c3BT1SCh9Tw4PhjFttJOuZMYJFM+vM=; b=PfHNFzQ9rCBlVIO63OVqH47rvQEgXn8oCSbJfxKNQ89md4y1zGBWHxhXb10Dr4RB3IH8D3 kUq0ona/p75B9QgwRngG5sfd0tb0WRKQtyeu8AH+WXgCCYCC/PN0OHtt5PTlr03wDGtyq3 ccByb69WBbZeKqpcF6gelsTciZAv1Sc= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-151-CBWU-I71PTmksMhS8Bk3tA-1; Sun, 04 Sep 2022 23:19:10 -0400 X-MC-Unique: CBWU-I71PTmksMhS8Bk3tA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D14EC29AA2F5; Mon, 5 Sep 2022 03:19:09 +0000 (UTC) Received: from localhost (ovpn-12-58.pek2.redhat.com [10.72.12.58]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 810A44010E4D; Mon, 5 Sep 2022 03:19:08 +0000 (UTC) Date: Mon, 5 Sep 2022 11:19:05 +0800 From: Baoquan He To: Eric DeVolder Cc: linux-kernel@vger.kernel.org, x86@kernel.org, kexec@lists.infradead.org, ebiederm@xmission.com, dyoung@redhat.com, vgoyal@redhat.com, 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, david@redhat.com, sourabhjain@linux.ibm.com, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com Subject: Re: [PATCH v11 7/7] x86/crash: Add x86 crash hotplug support Message-ID: References: <20220826173704.1895-1-eric.devolder@oracle.com> <20220826173704.1895-8-eric.devolder@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220826173704.1895-8-eric.devolder@oracle.com> X-Scanned-By: MIMEDefang 2.84 on 10.11.54.2 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/26/22 at 01:37pm, 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 > --- > arch/x86/Kconfig | 11 ++++ > arch/x86/include/asm/kexec.h | 20 +++++++ > arch/x86/kernel/crash.c | 102 +++++++++++++++++++++++++++++++++++ > 3 files changed, 133 insertions(+) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index f9920f1341c8..cdfc9b2fdf98 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -2056,6 +2056,17 @@ 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/include/asm/kexec.h b/arch/x86/include/asm/kexec.h > index a3760ca796aa..432073385b2d 100644 > --- a/arch/x86/include/asm/kexec.h > +++ b/arch/x86/include/asm/kexec.h > @@ -212,6 +212,26 @@ typedef void crash_vmclear_fn(void); > extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss; > extern void kdump_nmi_shootdown_cpus(void); > > +void *arch_map_crash_pages(unsigned long paddr, unsigned long size); > +#define arch_map_crash_pages arch_map_crash_pages > + > +void arch_unmap_crash_pages(void **ptr); > +#define arch_unmap_crash_pages arch_unmap_crash_pages > + > +void arch_crash_handle_hotplug_event(struct kimage *image, > + unsigned int hp_action); > +#define arch_crash_handle_hotplug_event arch_crash_handle_hotplug_event > + > +#ifdef CONFIG_HOTPLUG_CPU > +static inline int crash_hotplug_cpu_support(void) { return 1; } > +#define crash_hotplug_cpu_support crash_hotplug_cpu_support > +#endif > + > +#ifdef CONFIG_MEMORY_HOTPLUG > +static inline int crash_hotplug_memory_support(void) { return 1; } > +#define crash_hotplug_memory_support crash_hotplug_memory_support > +#endif Check these two functions again, wonder whether this is a common usage to show support of a feature. I don't remember where we do like this. We usually define a global variable to mark it? Anyway, it works. See if other people have comments, I could be ignorant. Other than this tiny concern, this patch looks good to me: Acked-by: Baoquan He > + > #endif /* __ASSEMBLY__ */ > > #endif /* _ASM_X86_KEXEC_H */ > diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c > index 9ceb93c176a6..8fc7d678ac72 100644 > --- a/arch/x86/kernel/crash.c > +++ b/arch/x86/kernel/crash.c > @@ -25,6 +25,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -397,7 +398,18 @@ 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); > + /* Mark as usable to crash kernel, else crash kernel fails on boot */ > + image->elf_headers_sz = kbuf.memsz; > + 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); > @@ -412,3 +424,93 @@ int crash_load_segments(struct kimage *image) > return ret; > } > #endif /* CONFIG_KEXEC_FILE */ > + > +#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG) > +/* > + * 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 *arch_map_crash_pages(unsigned long paddr, unsigned long size) > +{ > + void *ptr = NULL; > + > + if (size > 0) { > + struct page *page = pfn_to_page(paddr >> PAGE_SHIFT); > + > + ptr = kmap_local_page(page); > + } > + > + return ptr; > +} > + > +void arch_unmap_crash_pages(void **ptr) > +{ > + if (ptr) { > + if (*ptr) > + kunmap_local(*ptr); > + *ptr = NULL; > + } > +} > + > +/** > + * arch_crash_handle_hotplug_event() - Handle hotplug elfcorehdr changes > + * @image: the active struct kimage > + * @hp_action: the hot un/plug action being handled > + * > + * 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, > + unsigned int hp_action) > +{ > + struct kexec_segment *ksegment; > + unsigned char *ptr = NULL; > + unsigned long elfsz = 0; > + void *elfbuf = NULL; > + unsigned long mem, memsz; > + > + /* > + * Elfcorehdr_index_valid checked in crash_core:handle_hotplug_event() > + */ > + ksegment = &image->segment[image->elfcorehdr_index]; > + mem = ksegment->mem; > + memsz = ksegment->memsz; > + > + /* > + * Create the new elfcorehdr reflecting the changes to CPU and/or > + * memory resources. > + */ > + 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 = arch_map_crash_pages(mem, memsz); > + if (ptr) { > + /* > + * Temporarily invalidate the crash image while the > + * elfcorehdr is updated. > + */ > + xchg(&kexec_crash_image, NULL); > + memcpy_flushcache((void *)ptr, elfbuf, elfsz); > + xchg(&kexec_crash_image, image); > + } > + arch_unmap_crash_pages((void **)&ptr); > + pr_debug("crash hp: re-loaded elfcorehdr at 0x%lx\n", mem); > + > +out: > + if (elfbuf) > + vfree(elfbuf); > +} > +#endif > -- > 2.31.1 >