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[2620:137:e000::1:20]) by mx.google.com with ESMTP id ee42-20020a056402292a00b00410875aa4b8si986869edb.381.2022.03.03.03.00.27; Thu, 03 Mar 2022 03:00:50 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=BMc3h4ER; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232063AbiCCK2e (ORCPT + 99 others); Thu, 3 Mar 2022 05:28:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58934 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229665AbiCCK2d (ORCPT ); Thu, 3 Mar 2022 05:28:33 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 0966E10FE7 for ; Thu, 3 Mar 2022 02:27:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1646303265; 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=ESDfPkpzdO/GRRxJlraJfXW+JEa1V/JWH+0g5PNHMsA=; b=BMc3h4ERLmFVAueo+e4U9vbMhKaLdC8avB2VV/3bbKWGdWn5l6e2yDuIdpH1L+GIrpzdLe aGBoZatZMZlqVlZmXwlrhk0xY9rmZT0f+R1cB7jxYujMKS+SivxffyrCQupvTl3KH20QwV mAqAwdwmmD9Q/zJMnjz+MCp7wuVotxE= 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-117-43zrGepVMI-V4jafoNo52g-1; Thu, 03 Mar 2022 05:27:43 -0500 X-MC-Unique: 43zrGepVMI-V4jafoNo52g-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7147C520F; Thu, 3 Mar 2022 10:27:40 +0000 (UTC) Received: from localhost (ovpn-13-148.pek2.redhat.com [10.72.13.148]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E93C77610F; Thu, 3 Mar 2022 10:27:19 +0000 (UTC) Date: Thu, 3 Mar 2022 18:27:16 +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: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Spam-Status: No, score=-3.2 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/01/22 at 02:12pm, Eric DeVolder wrote: > > > On 2/22/22 22:10, Baoquan He wrote: > > 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 > Done! > > > > And also update other subject to reflect under which component the > > changes are made, crash hp is the feature name. > Here's what I have at the moment, is this matching expectation? > > pick 891fcff41a8f crash: fix minor typo/bug in debug message It's x86 code change, shoud be: x86/crash: fix minor typo/bug in debug message Others are similar. > pick 8f44e0d695be crash hp: Introduce CRASH_HOTPLUG configuration options > pick bae60e9db6ad crash: prototype change for crash_prepare_elf64_headers > pick cb98d1d923c8 crash: generic crash hotplug support infrastructure > pick 40e4434abad4 kexec: exclude elfcorehdr from the segment digest > pick 75039922aedc kexec: exclude hot remove cpu from elfcorehdr notes > pick 0be483dadeb8 x86/kexec: Add x86 crash hotplug support for kexec_file_load > pick 388bb5e4bf9a x86/kexec: Add x86 crash hotplug support for kexec_load > > > > > Otherwise, this looks good to me. > Thanks! > eric > > > > > > > > > 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 > > > > > >