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Thu, 22 Feb 2024 03:31:51 GMT Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id ACCC620040; Thu, 22 Feb 2024 03:31:49 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8452520043; Thu, 22 Feb 2024 03:31:38 +0000 (GMT) Received: from [9.61.79.25] (unknown [9.61.79.25]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 22 Feb 2024 03:31:38 +0000 (GMT) Message-ID: <8af4b0ec-9e0c-4023-ab66-98bb8e9f914d@linux.ibm.com> Date: Thu, 22 Feb 2024 09:01:36 +0530 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v16 2/5] crash: add a new kexec flag for hotplug support Content-Language: en-US To: Baoquan He References: <20240217081452.164571-1-sourabhjain@linux.ibm.com> <20240217081452.164571-3-sourabhjain@linux.ibm.com> From: Sourabh Jain In-Reply-To: <20240217081452.164571-3-sourabhjain@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: pd_VZXyMw6afFLbANNBoVDyzxmKIjbuR X-Proofpoint-GUID: VcA-Dhb2VriYUA6DQIwvWa1mgvxlh7eW Content-Transfer-Encoding: 7bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2024-02-22_01,2024-02-21_02,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=999 bulkscore=0 mlxscore=0 phishscore=0 suspectscore=0 clxscore=1015 spamscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 adultscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311290000 definitions=main-2402220025 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 , Baoquan He , 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" Hello Baoquan, There are a lot of code movements introduced by your patch series, 'Split crash out from kexec and clean up related config items.' https://lore.kernel.org/all/20240221125752.36fbfe9c307496313198b60f@linux-foundation.org/ Do you want me to rebase this patch series on top of the above patch series? Thanks, Sourabh Jain On 17/02/24 13:44, 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/kexec.h | 27 +++++++++++++++++---------- > include/uapi/linux/kexec.h | 1 + > kernel/crash_core.c | 11 ++++------- > kernel/kexec.c | 4 ++-- > kernel/kexec_file.c | 5 +++++ > 9 files changed, 50 insertions(+), 41 deletions(-) > > diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h > index 9bb6607e864e..8be622e82ba8 100644 > --- a/arch/x86/include/asm/kexec.h > +++ b/arch/x86/include/asm/kexec.h > @@ -211,15 +211,8 @@ 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 44744e9c68ec..7072aaee2ea0 100644 > --- a/arch/x86/kernel/crash.c > +++ b/arch/x86/kernel/crash.c > @@ -398,20 +398,26 @@ 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 47de0f140ba6..24eb52607151 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 14f964a7719b..b80be8193970 100644 > --- a/drivers/base/memory.c > +++ b/drivers/base/memory.c > @@ -514,7 +514,7 @@ 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/kexec.h b/include/linux/kexec.h > index 802052d9c64b..175152b99cb7 100644 > --- a/include/linux/kexec.h > +++ b/include/linux/kexec.h > @@ -317,8 +317,10 @@ 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 > @@ -396,9 +398,10 @@ 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 */ > @@ -486,14 +489,18 @@ static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages) { > 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 arch_crash_hotplug_support > +static inline int arch_crash_hotplug_support(struct kimage *image, unsigned long kexec_flags) > +{ > > -#ifndef crash_hotplug_memory_support > -static inline int crash_hotplug_memory_support(void) { return 0; } > +#ifdef CONFIG_KEXEC_FILE > + if (image->file_mode) > + return 1; > +#endif > + return kexec_flags & KEXEC_CRASH_HOTPLUG_SUPPORT; > +} > #endif > > #ifndef crash_get_elfcorehdr_size > 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 b692ec5955de..3142884a5a5b 100644 > --- a/kernel/crash_core.c > +++ b/kernel/crash_core.c > @@ -886,7 +886,7 @@ 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; > > @@ -898,10 +898,7 @@ 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(); > @@ -942,8 +939,8 @@ 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 8f35a5a42af8..9dc5b7ed5b73 100644 > --- a/kernel/kexec.c > +++ b/kernel/kexec.c > @@ -130,8 +130,8 @@ 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 bef2f6f2571b..4dddf9264a69 100644 > --- a/kernel/kexec_file.c > +++ b/kernel/kexec_file.c > @@ -373,6 +373,11 @@ 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;