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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8CC29C54798 for ; Thu, 29 Feb 2024 05:57:10 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=G9gP8Rg+; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4TlgTw6qnbz3dmy for ; Thu, 29 Feb 2024 16:57:08 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=G9gP8Rg+; dkim-atps=neutral Received: from gandalf.ozlabs.org (mail.ozlabs.org [IPv6:2404:9400:2221:ea00::3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4TlgT25DR6z3bsQ for ; Thu, 29 Feb 2024 16:56:22 +1100 (AEDT) Received: from gandalf.ozlabs.org (gandalf.ozlabs.org [150.107.74.76]) by gandalf.ozlabs.org (Postfix) with ESMTP id 4TlgT24yYhz4wc5 for ; Thu, 29 Feb 2024 16:56:22 +1100 (AEDT) Received: by gandalf.ozlabs.org (Postfix) id 4TlgT24v19z4wc7; Thu, 29 Feb 2024 16:56:22 +1100 (AEDT) Authentication-Results: gandalf.ozlabs.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: gandalf.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=G9gP8Rg+; dkim-atps=neutral Authentication-Results: gandalf.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=redhat.com (client-ip=170.10.129.124; helo=us-smtp-delivery-124.mimecast.com; envelope-from=bhe@redhat.com; receiver=ozlabs.org) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) by gandalf.ozlabs.org (Postfix) with ESMTPS id 4TlgT16sHhz4wc5 for ; Thu, 29 Feb 2024 16:56:21 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1709186179; 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=PAIgBGO6G8y2Ki/n2ZSEuvfNZqACiPoGuCSfmEbEjqA=; b=G9gP8Rg+ihq00DTriZMiPT855ZWlRMIhG7Pkcj4K3QSADRAPIavPSLto+ywUdpCkxZk0Bp bIwbMttn9vLLSj/t9612U00Z7YGrpKwE8/hjmvV6avwt/VwBsvrvDyGFg4LY20v+a75eaR 6fwXp6brxkmguoisCkAcalwvAeQTU1A= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-275-5G5crAYXNOeAzyl6MYGvlA-1; Thu, 29 Feb 2024 00:56:13 -0500 X-MC-Unique: 5G5crAYXNOeAzyl6MYGvlA-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6B9FA845E61; Thu, 29 Feb 2024 05:56:12 +0000 (UTC) Received: from localhost (unknown [10.72.116.6]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 920F6492BC6; Thu, 29 Feb 2024 05:56:10 +0000 (UTC) Date: Thu, 29 Feb 2024 13:56:07 +0800 From: Baoquan He To: Sourabh Jain Subject: Re: [PATCH v17 2/6] crash: add a new kexec flag for hotplug support Message-ID: References: <20240226084118.16310-1-sourabhjain@linux.ibm.com> <20240226084118.16310-3-sourabhjain@linux.ibm.com> <40de57a1-0a09-4c6a-bf38-04ea5dc2d48b@linux.ibm.com> MIME-Version: 1.0 In-Reply-To: <40de57a1-0a09-4c6a-bf38-04ea5dc2d48b@linux.ibm.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.9 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: David Hildenbrand , Dave Hansen , Mimi Zohar , linuxppc-dev@ozlabs.org, Eric DeVolder , Boris Ostrovsky , Valentin Schneider , x86@kernel.org, "Aneesh Kumar K . V" , Laurent Dufour , Dave Young , Vivek Goyal , Naveen N Rao , Borislav Petkov , Thomas Gleixner , Hari Bathini , Oscar Salvador , Greg Kroah-Hartman , kexec@lists.infradead.org, Mahesh Salgaonkar , Akhil Raj , Andrew Morton Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 02/29/24 at 10:35am, Sourabh Jain wrote: > Hello Baoquan, > > Do you have any comments or suggestions for this patch series, especially > for this patch? Have applied this series and reviewing, will ack or add comment if any concern. Thanks. > On 26/02/24 14:11, Sourabh Jain wrote: > > Commit a72bbec70da2 ("crash: hotplug support for kexec_load()") > > introduced a new kexec flag, `KEXEC_UPDATE_ELFCOREHDR`. Kexec tool uses > > this flag to indicate to the kernel that it is safe to modify the > > elfcorehdr of the kdump image loaded using the kexec_load system call. > > > > However, it is possible that architectures may need to update kexec > > segments other then elfcorehdr. For example, FDT (Flatten Device Tree) > > on PowerPC. Introducing a new kexec flag for every new kexec segment > > may not be a good solution. Hence, a generic kexec flag bit, > > `KEXEC_CRASH_HOTPLUG_SUPPORT`, is introduced to share the CPU/Memory > > hotplug support intent between the kexec tool and the kernel for the > > kexec_load system call. > > > > Now, if the kexec tool sends KEXEC_CRASH_HOTPLUG_SUPPORT kexec flag to > > the kernel, it indicates to the kernel that all the required kexec > > segment is skipped from SHA calculation and it is safe to update kdump > > image loaded using the kexec_load syscall. > > > > While loading the kdump image using the kexec_load syscall, the > > @update_elfcorehdr member of struct kimage is set if the kexec tool > > sends the KEXEC_UPDATE_ELFCOREHDR kexec flag. This member is later used > > to determine whether it is safe to update elfcorehdr on hotplug events. > > However, with the introduction of the KEXEC_CRASH_HOTPLUG_SUPPORT kexec > > flag, the kexec tool could mark all the required kexec segments on an > > architecture as safe to update. So rename the @update_elfcorehdr to > > @hotplug_support. If @hotplug_support is set, the kernel can safely > > update all the required kexec segments of the kdump image during > > CPU/Memory hotplug events. > > > > Introduce an architecture-specific function to process kexec flags for > > determining hotplug support. Set the @hotplug_support member of struct > > kimage for both kexec_load and kexec_file_load system calls. This > > simplifies kernel checks to identify hotplug support for the currently > > loaded kdump image by just examining the value of @hotplug_support. > > > > Signed-off-by: Sourabh Jain > > Cc: Akhil Raj > > Cc: Andrew Morton > > Cc: Aneesh Kumar K.V > > Cc: Baoquan He > > Cc: Borislav Petkov (AMD) > > Cc: Boris Ostrovsky > > Cc: Christophe Leroy > > Cc: Dave Hansen > > Cc: Dave Young > > Cc: David Hildenbrand > > Cc: Eric DeVolder > > Cc: Greg Kroah-Hartman > > Cc: Hari Bathini > > Cc: Laurent Dufour > > Cc: Mahesh Salgaonkar > > Cc: Michael Ellerman > > Cc: Mimi Zohar > > Cc: Naveen N Rao > > Cc: Oscar Salvador > > Cc: Thomas Gleixner > > Cc: Valentin Schneider > > Cc: Vivek Goyal > > Cc: kexec@lists.infradead.org > > Cc: x86@kernel.org > > --- > > arch/x86/include/asm/kexec.h | 11 ++--------- > > arch/x86/kernel/crash.c | 28 +++++++++++++++++----------- > > drivers/base/cpu.c | 2 +- > > drivers/base/memory.c | 2 +- > > include/linux/crash_core.h | 13 ++++++------- > > include/linux/kexec.h | 11 +++++++---- > > include/uapi/linux/kexec.h | 1 + > > kernel/crash_core.c | 11 ++++------- > > kernel/kexec.c | 4 ++-- > > kernel/kexec_file.c | 5 +++++ > > 10 files changed, 46 insertions(+), 42 deletions(-) > > > > diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h > > index cb1320ebbc23..ae5482a2f0ca 100644 > > --- a/arch/x86/include/asm/kexec.h > > +++ b/arch/x86/include/asm/kexec.h > > @@ -210,15 +210,8 @@ extern void kdump_nmi_shootdown_cpus(void); > > void arch_crash_handle_hotplug_event(struct kimage *image, void *arg); > > #define arch_crash_handle_hotplug_event arch_crash_handle_hotplug_event > > -#ifdef CONFIG_HOTPLUG_CPU > > -int arch_crash_hotplug_cpu_support(void); > > -#define crash_hotplug_cpu_support arch_crash_hotplug_cpu_support > > -#endif > > - > > -#ifdef CONFIG_MEMORY_HOTPLUG > > -int arch_crash_hotplug_memory_support(void); > > -#define crash_hotplug_memory_support arch_crash_hotplug_memory_support > > -#endif > > +int arch_crash_hotplug_support(struct kimage *image, unsigned long kexec_flags); > > +#define arch_crash_hotplug_support arch_crash_hotplug_support > > unsigned int arch_crash_get_elfcorehdr_size(void); > > #define crash_get_elfcorehdr_size arch_crash_get_elfcorehdr_size > > diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c > > index 2a682fe86352..f06501445cd9 100644 > > --- a/arch/x86/kernel/crash.c > > +++ b/arch/x86/kernel/crash.c > > @@ -402,20 +402,26 @@ int crash_load_segments(struct kimage *image) > > #undef pr_fmt > > #define pr_fmt(fmt) "crash hp: " fmt > > -/* These functions provide the value for the sysfs crash_hotplug nodes */ > > -#ifdef CONFIG_HOTPLUG_CPU > > -int arch_crash_hotplug_cpu_support(void) > > +int arch_crash_hotplug_support(struct kimage *image, unsigned long kexec_flags) > > { > > - return crash_check_update_elfcorehdr(); > > -} > > -#endif > > -#ifdef CONFIG_MEMORY_HOTPLUG > > -int arch_crash_hotplug_memory_support(void) > > -{ > > - return crash_check_update_elfcorehdr(); > > -} > > +#ifdef CONFIG_KEXEC_FILE > > + if (image->file_mode) > > + return 1; > > #endif > > + /* > > + * Initially, crash hotplug support for kexec_load was added > > + * with the KEXEC_UPDATE_ELFCOREHDR flag. Later, this > > + * functionality was expanded to accommodate multiple kexec > > + * segment updates, leading to the introduction of the > > + * KEXEC_CRASH_HOTPLUG_SUPPORT kexec flag bit. Consequently, > > + * when the kexec tool sends either of these flags, it indicates > > + * that the required kexec segment (elfcorehdr) is excluded from > > + * the SHA calculation. > > + */ > > + return (kexec_flags & KEXEC_UPDATE_ELFCOREHDR || > > + kexec_flags & KEXEC_CRASH_HOTPLUG_SUPPORT); > > +} > > unsigned int arch_crash_get_elfcorehdr_size(void) > > { > > diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c > > index 5ae1496ccc06..a23489b8c8f0 100644 > > --- a/drivers/base/cpu.c > > +++ b/drivers/base/cpu.c > > @@ -306,7 +306,7 @@ static ssize_t crash_hotplug_show(struct device *dev, > > struct device_attribute *attr, > > char *buf) > > { > > - return sysfs_emit(buf, "%d\n", crash_hotplug_cpu_support()); > > + return sysfs_emit(buf, "%d\n", crash_check_hotplug_support()); > > } > > static DEVICE_ATTR_ADMIN_RO(crash_hotplug); > > #endif > > diff --git a/drivers/base/memory.c b/drivers/base/memory.c > > index c0436f46cfb7..67858eeb92ed 100644 > > --- a/drivers/base/memory.c > > +++ b/drivers/base/memory.c > > @@ -535,7 +535,7 @@ static DEVICE_ATTR_RW(auto_online_blocks); > > static ssize_t crash_hotplug_show(struct device *dev, > > struct device_attribute *attr, char *buf) > > { > > - return sysfs_emit(buf, "%d\n", crash_hotplug_memory_support()); > > + return sysfs_emit(buf, "%d\n", crash_check_hotplug_support()); > > } > > static DEVICE_ATTR_RO(crash_hotplug); > > #endif > > diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h > > index 647e928efee8..44305336314e 100644 > > --- a/include/linux/crash_core.h > > +++ b/include/linux/crash_core.h > > @@ -40,14 +40,13 @@ static inline void arch_kexec_unprotect_crashkres(void) { } > > static inline void arch_crash_handle_hotplug_event(struct kimage *image, void *arg) { } > > #endif > > -int crash_check_update_elfcorehdr(void); > > +int crash_check_hotplug_support(void); > > -#ifndef crash_hotplug_cpu_support > > -static inline int crash_hotplug_cpu_support(void) { return 0; } > > -#endif > > - > > -#ifndef crash_hotplug_memory_support > > -static inline int crash_hotplug_memory_support(void) { return 0; } > > +#ifndef arch_crash_hotplug_support > > +static inline int arch_crash_hotplug_support(struct kimage *image, unsigned long kexec_flags) > > +{ > > + return 0; > > +} > > #endif > > #ifndef crash_get_elfcorehdr_size > > diff --git a/include/linux/kexec.h b/include/linux/kexec.h > > index 060835bb82d5..5b93a5767413 100644 > > --- a/include/linux/kexec.h > > +++ b/include/linux/kexec.h > > @@ -319,8 +319,10 @@ struct kimage { > > /* If set, we are using file mode kexec syscall */ > > unsigned int file_mode:1; > > #ifdef CONFIG_CRASH_HOTPLUG > > - /* If set, allow changes to elfcorehdr of kexec_load'd image */ > > - unsigned int update_elfcorehdr:1; > > + /* If set, it is safe to update kexec segments that are > > + * excluded from SHA calculation. > > + */ > > + unsigned int hotplug_support:1; > > #endif > > #ifdef ARCH_HAS_KIMAGE_ARCH > > @@ -391,9 +393,10 @@ bool kexec_load_permitted(int kexec_image_type); > > /* List of defined/legal kexec flags */ > > #ifndef CONFIG_KEXEC_JUMP > > -#define KEXEC_FLAGS (KEXEC_ON_CRASH | KEXEC_UPDATE_ELFCOREHDR) > > +#define KEXEC_FLAGS (KEXEC_ON_CRASH | KEXEC_UPDATE_ELFCOREHDR | KEXEC_CRASH_HOTPLUG_SUPPORT) > > #else > > -#define KEXEC_FLAGS (KEXEC_ON_CRASH | KEXEC_PRESERVE_CONTEXT | KEXEC_UPDATE_ELFCOREHDR) > > +#define KEXEC_FLAGS (KEXEC_ON_CRASH | KEXEC_PRESERVE_CONTEXT | KEXEC_UPDATE_ELFCOREHDR | \ > > + KEXEC_CRASH_HOTPLUG_SUPPORT) > > #endif > > /* List of defined/legal kexec file flags */ > > diff --git a/include/uapi/linux/kexec.h b/include/uapi/linux/kexec.h > > index c17bb096ea68..5ae1741ea8ea 100644 > > --- a/include/uapi/linux/kexec.h > > +++ b/include/uapi/linux/kexec.h > > @@ -13,6 +13,7 @@ > > #define KEXEC_ON_CRASH 0x00000001 > > #define KEXEC_PRESERVE_CONTEXT 0x00000002 > > #define KEXEC_UPDATE_ELFCOREHDR 0x00000004 > > +#define KEXEC_CRASH_HOTPLUG_SUPPORT 0x00000008 > > #define KEXEC_ARCH_MASK 0xffff0000 > > /* > > diff --git a/kernel/crash_core.c b/kernel/crash_core.c > > index 70fa8111a9d6..630c4fd7ea39 100644 > > --- a/kernel/crash_core.c > > +++ b/kernel/crash_core.c > > @@ -496,7 +496,7 @@ static DEFINE_MUTEX(__crash_hotplug_lock); > > * It reflects the kernel's ability/permission to update the crash > > * elfcorehdr directly. > > */ > > -int crash_check_update_elfcorehdr(void) > > +int crash_check_hotplug_support(void) > > { > > int rc = 0; > > @@ -508,10 +508,7 @@ int crash_check_update_elfcorehdr(void) > > return 0; > > } > > if (kexec_crash_image) { > > - if (kexec_crash_image->file_mode) > > - rc = 1; > > - else > > - rc = kexec_crash_image->update_elfcorehdr; > > + rc = kexec_crash_image->hotplug_support; > > } > > /* Release lock now that update complete */ > > kexec_unlock(); > > @@ -552,8 +549,8 @@ static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu, > > image = kexec_crash_image; > > - /* Check that updating elfcorehdr is permitted */ > > - if (!(image->file_mode || image->update_elfcorehdr)) > > + /* Check that kexec segments update is permitted */ > > + if (!image->hotplug_support) > > goto out; > > if (hp_action == KEXEC_CRASH_HP_ADD_CPU || > > diff --git a/kernel/kexec.c b/kernel/kexec.c > > index bab542fc1463..a6b3f96bb50c 100644 > > --- a/kernel/kexec.c > > +++ b/kernel/kexec.c > > @@ -135,8 +135,8 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments, > > image->preserve_context = 1; > > #ifdef CONFIG_CRASH_HOTPLUG > > - if (flags & KEXEC_UPDATE_ELFCOREHDR) > > - image->update_elfcorehdr = 1; > > + if ((flags & KEXEC_ON_CRASH) && arch_crash_hotplug_support(image, flags)) > > + image->hotplug_support = 1; > > #endif > > ret = machine_kexec_prepare(image); > > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c > > index 2d1db05fbf04..3d64290d24c9 100644 > > --- a/kernel/kexec_file.c > > +++ b/kernel/kexec_file.c > > @@ -376,6 +376,11 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd, > > if (ret) > > goto out; > > +#ifdef CONFIG_CRASH_HOTPLUG > > + if ((flags & KEXEC_FILE_ON_CRASH) && arch_crash_hotplug_support(image, flags)) > > + image->hotplug_support = 1; > > +#endif > > + > > ret = machine_kexec_prepare(image); > > if (ret) > > goto out; >