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oracle.com X-MS-Exchange-CrossTenant-Network-Message-Id: 0e9c7625-b475-488c-6ae5-08db6c224bbf X-MS-Exchange-CrossTenant-AuthSource: CO1PR10MB4531.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Jun 2023 15:24:36.1044 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: aLXJ7Imoq0HjwCp26X6yHGcrBUsO70d0rMJylr7OqkY215sYzK6Wb5ua/yX2XrKqOxk2XS9y4ex0HwmSUPApS7pAn0Pg9+FJ3GgnJ2lDlGM= X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR10MB4163 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.957,Hydra:6.0.573,FMLib:17.11.176.26 definitions=2023-06-13_18,2023-06-12_02,2023-05-22_02 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 phishscore=0 malwarescore=0 mlxscore=0 adultscore=0 bulkscore=0 spamscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2305260000 definitions=main-2306130136 X-Proofpoint-ORIG-GUID: cgQFTKcgfbRT3pqDiPagsWZrd21qwGIl X-Proofpoint-GUID: cgQFTKcgfbRT3pqDiPagsWZrd21qwGIl X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230613_082500_918733_3D154519 X-CRM114-Status: GOOD ( 14.54 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org On 6/13/23 03:03, Greg KH wrote: > On Mon, Jun 12, 2023 at 05:07:08PM -0400, Eric DeVolder wrote: >> Introduce the crash_hotplug attribute for memory and CPUs for >> use by userspace. These attributes directly facilitate the udev >> rule for managing userspace re-loading of the crash kernel upon >> hot un/plug changes. >> >> For memory, expose the crash_hotplug attribute to the >> /sys/devices/system/memory directory. For example: >> >> # udevadm info --attribute-walk /sys/devices/system/memory/memory81 >> looking at device '/devices/system/memory/memory81': >> KERNEL=="memory81" >> SUBSYSTEM=="memory" >> DRIVER=="" >> ATTR{online}=="1" >> ATTR{phys_device}=="0" >> ATTR{phys_index}=="00000051" >> ATTR{removable}=="1" >> ATTR{state}=="online" >> ATTR{valid_zones}=="Movable" >> >> looking at parent device '/devices/system/memory': >> KERNELS=="memory" >> SUBSYSTEMS=="" >> DRIVERS=="" >> ATTRS{auto_online_blocks}=="offline" >> ATTRS{block_size_bytes}=="8000000" >> ATTRS{crash_hotplug}=="1" >> >> For CPUs, expose the crash_hotplug attribute to the >> /sys/devices/system/cpu directory. For example: >> >> # udevadm info --attribute-walk /sys/devices/system/cpu/cpu0 >> looking at device '/devices/system/cpu/cpu0': >> KERNEL=="cpu0" >> SUBSYSTEM=="cpu" >> DRIVER=="processor" >> ATTR{crash_notes}=="277c38600" >> ATTR{crash_notes_size}=="368" >> ATTR{online}=="1" >> >> looking at parent device '/devices/system/cpu': >> KERNELS=="cpu" >> SUBSYSTEMS=="" >> DRIVERS=="" >> ATTRS{crash_hotplug}=="1" >> ATTRS{isolated}=="" >> ATTRS{kernel_max}=="8191" >> ATTRS{nohz_full}==" (null)" >> ATTRS{offline}=="4-7" >> ATTRS{online}=="0-3" >> ATTRS{possible}=="0-7" >> ATTRS{present}=="0-3" >> >> With these sysfs attributes in place, it is possible to efficiently >> instruct the udev rule to skip crash kernel reloading for kernels >> configured with crash hotplug support. >> >> For example, the following is the proposed udev rule change for RHEL >> system 98-kexec.rules (as the first lines of the rule file): >> >> # The kernel updates the crash elfcorehdr for CPU and memory changes >> SUBSYSTEM=="cpu", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end" >> SUBSYSTEM=="memory", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end" >> >> When examined in the context of 98-kexec.rules, the above rules >> test if crash_hotplug is set, and if so, the userspace initiated >> unload-then-reload of the crash kernel is skipped. >> >> CPU and memory checks are separated in accordance with >> CONFIG_HOTPLUG_CPU and CONFIG_MEMORY_HOTPLUG kernel config options. >> If an architecture supports, for example, memory hotplug but not >> CPU hotplug, then the /sys/devices/system/memory/crash_hotplug >> attribute file is present, but the /sys/devices/system/cpu/crash_hotplug >> attribute file will NOT be present. Thus the udev rule skips >> userspace processing of memory hot un/plug events, but the udev >> rule will evaluate false for CPU events, thus allowing userspace to >> process CPU hot un/plug events (ie the unload-then-reload of the kdump >> capture kernel). >> >> Signed-off-by: Eric DeVolder >> Reviewed-by: Sourabh Jain >> Acked-by: Hari Bathini >> Acked-by: Baoquan He >> --- >> .../admin-guide/mm/memory-hotplug.rst | 8 ++++++++ >> Documentation/core-api/cpu_hotplug.rst | 18 ++++++++++++++++++ >> drivers/base/cpu.c | 14 ++++++++++++++ >> drivers/base/memory.c | 13 +++++++++++++ >> include/linux/kexec.h | 8 ++++++++ >> 5 files changed, 61 insertions(+) >> >> diff --git a/Documentation/admin-guide/mm/memory-hotplug.rst b/Documentation/admin-guide/mm/memory-hotplug.rst >> index 1b02fe5807cc..eb99d79223a3 100644 >> --- a/Documentation/admin-guide/mm/memory-hotplug.rst >> +++ b/Documentation/admin-guide/mm/memory-hotplug.rst >> @@ -291,6 +291,14 @@ The following files are currently defined: >> Availability depends on the CONFIG_ARCH_MEMORY_PROBE >> kernel configuration option. >> ``uevent`` read-write: generic udev file for device subsystems. >> +``crash_hotplug`` read-only: when changes to the system memory map >> + occur due to hot un/plug of memory, this file contains >> + '1' if the kernel updates the kdump capture kernel memory >> + map itself (via elfcorehdr), or '0' if userspace must update >> + the kdump capture kernel memory map. >> + >> + Availability depends on the CONFIG_MEMORY_HOTPLUG kernel >> + configuration option. >> ====================== ========================================================= >> >> .. note:: >> diff --git a/Documentation/core-api/cpu_hotplug.rst b/Documentation/core-api/cpu_hotplug.rst >> index f75778d37488..0c8dc3fe5f94 100644 >> --- a/Documentation/core-api/cpu_hotplug.rst >> +++ b/Documentation/core-api/cpu_hotplug.rst >> @@ -750,6 +750,24 @@ will receive all events. A script like:: >> >> can process the event further. >> >> +When changes to the CPUs in the system occur, the sysfs file >> +/sys/devices/system/cpu/crash_hotplug contains '1' if the kernel >> +updates the kdump capture kernel list of CPUs itself (via elfcorehdr), >> +or '0' if userspace must update the kdump capture kernel list of CPUs. >> + >> +The availability depends on the CONFIG_HOTPLUG_CPU kernel configuration >> +option. >> + >> +To skip userspace processing of CPU hot un/plug events for kdump >> +(ie the unload-then-reload to obtain a current list of CPUs), this sysfs >> +file can be used in a udev rule as follows: >> + >> + SUBSYSTEM=="cpu", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end" >> + >> +For a cpu hot un/plug event, if the architecture supports kernel updates >> +of the elfcorehdr (which contains the list of CPUs), then the rule skips >> +the unload-then-reload of the kdump capture kernel. >> + >> Kernel Inline Documentations Reference >> ====================================== >> >> diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c >> index c1815b9dae68..06a0c22b37b8 100644 >> --- a/drivers/base/cpu.c >> +++ b/drivers/base/cpu.c >> @@ -282,6 +282,17 @@ static ssize_t print_cpus_nohz_full(struct device *dev, >> static DEVICE_ATTR(nohz_full, 0444, print_cpus_nohz_full, NULL); >> #endif >> >> +#ifdef CONFIG_HOTPLUG_CPU >> +#include >> +static ssize_t crash_hotplug_show(struct device *dev, >> + struct device_attribute *attr, >> + char *buf) >> +{ >> + return sprintf(buf, "%d\n", crash_hotplug_cpu_support()); >> +} >> +static DEVICE_ATTR_ADMIN_RO(crash_hotplug); >> +#endif >> + >> static void cpu_device_release(struct device *dev) >> { >> /* >> @@ -469,6 +480,9 @@ static struct attribute *cpu_root_attrs[] = { >> #ifdef CONFIG_NO_HZ_FULL >> &dev_attr_nohz_full.attr, >> #endif >> +#ifdef CONFIG_HOTPLUG_CPU >> + &dev_attr_crash_hotplug.attr, >> +#endif >> #ifdef CONFIG_GENERIC_CPU_AUTOPROBE >> &dev_attr_modalias.attr, >> #endif >> diff --git a/drivers/base/memory.c b/drivers/base/memory.c >> index b456ac213610..24b8ef4c830c 100644 >> --- a/drivers/base/memory.c >> +++ b/drivers/base/memory.c >> @@ -490,6 +490,16 @@ static ssize_t auto_online_blocks_store(struct device *dev, >> >> static DEVICE_ATTR_RW(auto_online_blocks); >> >> +#ifdef CONFIG_MEMORY_HOTPLUG >> +#include >> +static ssize_t crash_hotplug_show(struct device *dev, >> + struct device_attribute *attr, char *buf) >> +{ >> + return sprintf(buf, "%d\n", crash_hotplug_memory_support()); >> +} > > This sysfs file has to be documented in Documentation/ABI/ right? I will add these entries. > > And did you use checkpatch? It should have told you to use sysfs_emit() > instead... I did use checkpatch, and it did not reveal that. [root@localhost linux]# ./scripts/checkpatch.pl --patch ../v23/0004-crash-memory-and-CPU-hotplug-sysfs-attributes.patch total: 0 errors, 0 warnings, 103 lines checked ../v23/0004-crash-memory-and-CPU-hotplug-sysfs-attributes.patch has no obvious style problems and is ready for submission. This is not the first time it's been suggested to me that checkpatch should have caught a problem; is there a different invocation than what I'm doing? > >> +static DEVICE_ATTR_RO(crash_hotplug); >> +#endif > > All of these #ifdefs should all be removed and instead use the > is_visible() callback to determine if the attribute is shown or not, > using the IS_ENABLED() test in the function. ok, I'll correct this. Thank you for looking at this! eric > > thanks, > > greg k-h _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec