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Mon, 10 Nov 2025 04:32:11 +0000 (GMT) From: Sourabh Jain To: linux-kernel@vger.kernel.org Cc: Sourabh Jain , Aditya Gupta , Andrew Morton , Baoquan he , Dave Young , Hari Bathini , Jiri Bohac , Madhavan Srinivasan , Mahesh J Salgaonkar , Pingfan Liu , "Ritesh Harjani (IBM)" , Shivang Upadhyay , Vivek Goyal , linuxppc-dev@lists.ozlabs.org, kexec@lists.infradead.org Subject: [PATCH v3 5/5] crash: export crashkernel CMA reservation to userspace Date: Mon, 10 Nov 2025 10:01:43 +0530 Message-ID: <20251110043143.484408-6-sourabhjain@linux.ibm.com> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20251110043143.484408-1-sourabhjain@linux.ibm.com> References: <20251110043143.484408-1-sourabhjain@linux.ibm.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=Ss+dKfO0 c=1 sm=1 tr=0 ts=69116ad4 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=6UeiqGixMTsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=Z4Rwk6OoAAAA:8 a=20KFwNOVAAAA:8 a=pGLkceISAAAA:8 a=voM4FWlXAAAA:8 a=JfrnYn6hAAAA:8 a=xHySkhmCpRGYbmLIrh4A:9 a=HkZW87K1Qel5hWWM3VKY:22 a=IC2XNlieTeVoXbcui8wp:22 a=1CNFftbPRP8L7MoqJWF3:22 a=cPQSjfK2_nFv0Q5t_7PE:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTA4MDA5NSBTYWx0ZWRfXxviF4FCwEarM yc1LY5Tu8GcyGsCVpQaqoUaZAVbe4a3a0MfS/jZRPM0K4YerWDDjCrxZ4u0MEKp6nA6nkAO5A4J 0J4ekljfk6jQ+VrV2IzSp05iLz3TeDqgE1uf3pkuQ3RnxOOPUbizgkJUo60HIy9FqO4pgCXNSRw tIJluGlaYzKM/qSOzRobVB8RJr/wPyA/ujXuR2vAJJCZ/f2I9ZV1VXv/dk7raSfM7tMHiY3Jbd4 TqGPQHr1oSH0uWp25QV5Gi9XFyJghieKKyMQbLXLn3a5iA79D0sNPj9Ut+ywciTf+5l6Sm7ynwe fdbBX86+jBjWirf8NHYvHO8QLk6dtl9VQGVbu82ztCSBJ/4jXc/xoHrIAZzrovnfTkj1UfK2bZ5 BPbpCkDTHwpaZ1SHaWNhIbT+X5yJFw== X-Proofpoint-GUID: auHh23VC4ON0syCQXH9zdfVE6uPG1e4W X-Proofpoint-ORIG-GUID: YOWHrtq7ZAwkVSY61seUoCGRKrnTKQYS X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-11-10_01,2025-11-06_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 suspectscore=0 impostorscore=0 bulkscore=0 phishscore=0 lowpriorityscore=0 adultscore=0 priorityscore=1501 spamscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511080095 Add a sysfs entry /sys/kernel/kexec/crash_cma_ranges to expose all CMA crashkernel ranges. This allows userspace tools configuring kdump to determine how much memory is reserved for crashkernel. If CMA is used, tools can warn users when attempting to capture user pages with CMA reservation. The new sysfs hold the CMA ranges in below format: cat /sys/kernel/kexec/crash_cma_ranges 100000000-10c7fffff Cc: Aditya Gupta Cc: Andrew Morton Cc: Baoquan he Cc: Dave Young Cc: Hari Bathini Cc: Jiri Bohac Cc: Madhavan Srinivasan Cc: Mahesh J Salgaonkar Cc: Pingfan Liu Cc: Ritesh Harjani (IBM) Cc: Shivang Upadhyay Cc: Vivek Goyal Cc: linuxppc-dev@lists.ozlabs.org Cc: kexec@lists.infradead.org Signed-off-by: Sourabh Jain --- Changelog: - Add the missing hunk to export crash_cma_ranges sysfs --- .../ABI/testing/sysfs-kernel-kexec-kdump | 10 ++++++++++ kernel/kexec_core.c | 17 +++++++++++++++++ 2 files changed, 27 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump index 00c00f380fea..f59051b5d96d 100644 --- a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump +++ b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump @@ -49,3 +49,13 @@ Description: read only is used by the user space utility kexec to support updating the in-kernel kdump image during hotplug operations. User: Kexec tools + +What: /sys/kernel/kexec/crash_cma_ranges +Date: Nov 2025 +Contact: kexec@lists.infradead.org +Description: read only + Provides information about the memory ranges reserved from + the Contiguous Memory Allocator (CMA) area that are allocated + to the crash (kdump) kernel. It lists the start and end physical + addresses of CMA regions assigned for crashkernel use. +User: kdump service diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index 7476a46de5d6..da6ff72b4669 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -1271,6 +1271,22 @@ static ssize_t crash_size_store(struct kobject *kobj, } static struct kobj_attribute crash_size_attr = __ATTR_RW(crash_size); +static ssize_t crash_cma_ranges_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + + ssize_t len = 0; + int i; + + for (i = 0; i < crashk_cma_cnt; ++i) { + len += sysfs_emit_at(buf, len, "%08llx-%08llx\n", + crashk_cma_ranges[i].start, + crashk_cma_ranges[i].end); + } + return len; +} +static struct kobj_attribute crash_cma_ranges_attr = __ATTR_RO(crash_cma_ranges); + #ifdef CONFIG_CRASH_HOTPLUG static ssize_t crash_elfcorehdr_size_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) @@ -1289,6 +1305,7 @@ static struct attribute *kexec_attrs[] = { #ifdef CONFIG_CRASH_DUMP &crash_loaded_attr.attr, &crash_size_attr.attr, + &crash_cma_ranges_attr.attr, #ifdef CONFIG_CRASH_HOTPLUG &crash_elfcorehdr_size_attr.attr, #endif -- 2.51.1