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Mon, 10 Nov 2025 02:08:53 -0500 X-MC-Unique: eeRdVSlDPZqYg8Icnng9Iw-1 X-Mimecast-MFC-AGG-ID: eeRdVSlDPZqYg8Icnng9Iw_1762758531 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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 mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 65A95195608F; Mon, 10 Nov 2025 07:08:50 +0000 (UTC) Received: from localhost (unknown [10.72.112.59]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B262E19560A7; Mon, 10 Nov 2025 07:08:47 +0000 (UTC) Date: Mon, 10 Nov 2025 15:08:41 +0800 From: Baoquan he To: Sourabh Jain Cc: linux-kernel@vger.kernel.org, Aditya Gupta , Andrew Morton , 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: Re: [PATCH v3 5/5] crash: export crashkernel CMA reservation to userspace Message-ID: References: <20251110043143.484408-1-sourabhjain@linux.ibm.com> <20251110043143.484408-6-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-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251110043143.484408-6-sourabhjain@linux.ibm.com> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 On 11/10/25 at 10:01am, Sourabh Jain wrote: > Add a sysfs entry /sys/kernel/kexec/crash_cma_ranges to expose all > CMA crashkernel ranges. I am not against this way. While wondering if it's more appropriate to export them into iomem_resource just like crashk_res and crashk_low_res doing. > > 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 >