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Fri, 8 Dec 2023 11:52:16 +0000 (GMT) From: Sourabh Jain To: linuxppc-dev@ozlabs.org Subject: [PATCH v6 2/3] powerpc/fadump: add hotplug_ready sysfs interface Date: Fri, 8 Dec 2023 17:21:58 +0530 Message-ID: <20231208115159.82236-3-sourabhjain@linux.ibm.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20231208115159.82236-1-sourabhjain@linux.ibm.com> References: <20231208115159.82236-1-sourabhjain@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: SlSfsBnRxeF1-O_H9tXfaFS72Nq6hdZA X-Proofpoint-ORIG-GUID: SlSfsBnRxeF1-O_H9tXfaFS72Nq6hdZA X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.997,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-12-08_06,2023-12-07_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 mlxscore=0 mlxlogscore=741 spamscore=0 clxscore=1015 phishscore=0 suspectscore=0 impostorscore=0 bulkscore=0 lowpriorityscore=0 adultscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311290000 definitions=main-2312080098 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: Mahesh Salgaonkar , Sourabh Jain , Naveen N Rao , "Aneesh Kumar K . V" , Aditya Gupta , Hari Bathini Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" The elfcorehdr describes the CPUs and memory of the crashed kernel to the kernel that captures the dump, known as the second or fadump kernel. The elfcorehdr needs to be updated if the system's memory changes due to memory hotplug or online/offline events. Currently, memory hotplug events are monitored in userspace by udev rules, and fadump is re-registered, which recreates the elfcorehdr with the latest available memory in the system. However, the previous patch ("powerpc: make fadump resilient with memory add/remove events") moved the creation of elfcorehdr to the second or fadump kernel. This eliminates the need to regenerate the elfcorehdr during memory hotplug or online/offline events. Create a sysfs entry at /sys/kernel/fadump/hotplug_ready to let userspace know that fadump re-registration is not required for memory add/remove events. Signed-off-by: Sourabh Jain Cc: Aditya Gupta Cc: Aneesh Kumar K.V Cc: Hari Bathini Cc: Mahesh Salgaonkar Cc: Michael Ellerman Cc: Naveen N Rao --- Documentation/ABI/testing/sysfs-kernel-fadump | 11 +++++++++++ arch/powerpc/kernel/fadump.c | 14 ++++++++++++++ 2 files changed, 25 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-kernel-fadump b/Documentation/ABI/testing/sysfs-kernel-fadump index 8f7a64a81783..971934b2891e 100644 --- a/Documentation/ABI/testing/sysfs-kernel-fadump +++ b/Documentation/ABI/testing/sysfs-kernel-fadump @@ -38,3 +38,14 @@ Contact: linuxppc-dev@lists.ozlabs.org Description: read only Provide information about the amount of memory reserved by FADump to save the crash dump in bytes. + +What: /sys/kernel/fadump/hotplug_ready +Date: Sep 2023 +Contact: linuxppc-dev@lists.ozlabs.org +Description: read only + Kdump udev rule re-registers fadump on memory add/remove events, + primarily to update the elfcorehdr. This sysfs indicates the + kdump udev rule that fadump re-registration is not required on + memory add/remove events because elfcorehdr is now prepared in + the second/fadump kernel. +User: kexec-tools diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c index eb9132538268..a55dd9bf754c 100644 --- a/arch/powerpc/kernel/fadump.c +++ b/arch/powerpc/kernel/fadump.c @@ -1455,6 +1455,18 @@ static ssize_t enabled_show(struct kobject *kobj, return sprintf(buf, "%d\n", fw_dump.fadump_enabled); } +/* + * /sys/kernel/fadump/hotplug_ready sysfs node returns 1, which inidcates + * to usersapce that fadump re-registration is not required on memory + * hotplug events. + */ +static ssize_t hotplug_ready_show(struct kobject *kobj, + struct kobj_attribute *attr, + char *buf) +{ + return sprintf(buf, "%d\n", 1); +} + static ssize_t mem_reserved_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) @@ -1527,11 +1539,13 @@ static struct kobj_attribute release_attr = __ATTR_WO(release_mem); static struct kobj_attribute enable_attr = __ATTR_RO(enabled); static struct kobj_attribute register_attr = __ATTR_RW(registered); static struct kobj_attribute mem_reserved_attr = __ATTR_RO(mem_reserved); +static struct kobj_attribute hotplug_ready_attr = __ATTR_RO(hotplug_ready); static struct attribute *fadump_attrs[] = { &enable_attr.attr, ®ister_attr.attr, &mem_reserved_attr.attr, + &hotplug_ready_attr.attr, NULL, }; -- 2.41.0