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 57F8DC433F5 for ; Wed, 23 Feb 2022 04:11:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237584AbiBWELd (ORCPT ); Tue, 22 Feb 2022 23:11:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38712 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231986AbiBWELc (ORCPT ); Tue, 22 Feb 2022 23:11:32 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 5BFBB66FAB for ; Tue, 22 Feb 2022 20:11:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1645589464; 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=Af9+WWK+R5EImF9noLlIgQ4gYNRPHI7xgUiLn28faM4=; b=jDyQ5GuB5eqUTChTo71Zydqtoq9sQXCOjjM2hzwZXKjZIm9n3Eb/4RqvwuF2zc/pigOHWI 3nemmyZLZdQ8tbf18uYXWdArdwo3nELdFQ7SkzzhqzsyFetKA6gZMxv9MvCIapf4dpXqnR Fj9gmb2ZTmxuJSJhY+/Uv8M7DBxYyhY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-224-tQcaiPVSPLqMj1_ldGcNoA-1; Tue, 22 Feb 2022 23:11:02 -0500 X-MC-Unique: tQcaiPVSPLqMj1_ldGcNoA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C8889824FA7; Wed, 23 Feb 2022 04:11:00 +0000 (UTC) Received: from localhost (ovpn-14-1.pek2.redhat.com [10.72.14.1]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2C91D4CEF9; Wed, 23 Feb 2022 04:10:55 +0000 (UTC) Date: Wed, 23 Feb 2022 12:10:51 +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, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com Subject: Re: [PATCH v4 09/10] crash hp: Add x86 crash hotplug support for kexec_file_load Message-ID: References: <20220209195706.51522-1-eric.devolder@oracle.com> <20220209195706.51522-10-eric.devolder@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220209195706.51522-10-eric.devolder@oracle.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/09/22 at 02:57pm, 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. Please mark the patch as X86 related by adding: x86/kexec: Add x86 crash hotplug support for kexec_file_load And also update other subject to reflect under which component the changes are made, crash hp is the feature name. Otherwise, this looks good to me. > > 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 > --- > 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 > #include > #include > +#include > > #include > #include > @@ -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 > From mboxrd@z Thu Jan 1 00:00:00 1970 From: Baoquan He Date: Wed, 23 Feb 2022 12:10:51 +0800 Subject: [PATCH v4 09/10] crash hp: Add x86 crash hotplug support for kexec_file_load In-Reply-To: <20220209195706.51522-10-eric.devolder@oracle.com> References: <20220209195706.51522-1-eric.devolder@oracle.com> <20220209195706.51522-10-eric.devolder@oracle.com> Message-ID: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: kexec@lists.infradead.org On 02/09/22 at 02:57pm, 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. Please mark the patch as X86 related by adding: x86/kexec: Add x86 crash hotplug support for kexec_file_load And also update other subject to reflect under which component the changes are made, crash hp is the feature name. Otherwise, this looks good to me. > > 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 > --- > 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 > #include > #include > +#include > > #include > #include > @@ -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 >