From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4209F302152 for ; Thu, 20 Nov 2025 09:59:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763632755; cv=none; b=tzZGHCTZng+VjNr/5pI/6AmnAUUbxu1bzBRJGmKgDFv16FDf3v5IkVTLROpsOvdwsxSr9GxMuvT7+agyJT+gPu0WohHvR3JlEJIAyTKw3G62eO09DgQt3oaBn6B22VqhMaX9AI8/Gb+IKAhXtjEgDqG2yo2fojwnw8fux/K/yYU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763632755; c=relaxed/simple; bh=ct+PicV31HUfTMFUt0x8pWh90nfdPiw1ihFiHFAbFtI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=TORUe9+8quD4z6wn7uHTotJ3US6piVs90d8ZfQCxsre1f+oAPHzg/eW0QH1NoB/dczDQkWWIGr49P0ee2yYitVRRLHOi0ij08A7z94BhxVKyQvon9o/aLhzmbPgEgcjTnV7VnQ4/iVFunVtetp4Hq6EiR1XlHVOsp/+vnsqPY8U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=gghxkviy; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="gghxkviy" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1763632751; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=zvIUpsoLZ7xdtMtpTpJeKuy6wYQI8+9FP33pXkKgVbw=; b=gghxkviyH5lNcThMOmC5nmKphAl0dbUI0ve0grgC5F/YdWbcAajEDzWda4LnjnX5atshA9 d/C9YB8C0yiM7OqPTA3hg1R6vh5B32hfr4bctBGWjijRQ+zVzfTyk7ryPBZ4Gyd6tDHYiZ 9wdMvHUNLz8UHaYg6NpxVryfs7yW0gY= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-562-Yej5Cc9sP6qjJ7YJ90kSXA-1; Thu, 20 Nov 2025 04:59:07 -0500 X-MC-Unique: Yej5Cc9sP6qjJ7YJ90kSXA-1 X-Mimecast-MFC-AGG-ID: Yej5Cc9sP6qjJ7YJ90kSXA_1763632746 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 666E01956094; Thu, 20 Nov 2025 09:59:05 +0000 (UTC) Received: from localhost (unknown [10.72.112.60]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 99C6230044DB; Thu, 20 Nov 2025 09:59:01 +0000 (UTC) Date: Thu, 20 Nov 2025 17:58:56 +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 v6] crash: export crashkernel CMA reservation to userspace Message-ID: References: <20251118071023.1673329-1-sourabhjain@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251118071023.1673329-1-sourabhjain@linux.ibm.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 On 11/18/25 at 12:40pm, Sourabh Jain wrote: > 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 > > The reason for not including Crash CMA Ranges in /proc/iomem is to avoid > conflicts. It has been observed that contiguous memory ranges are sometimes > shown as two separate System RAM entries in /proc/iomem. If a CMA range > overlaps two System RAM ranges, adding crashk_res to /proc/iomem can create > a conflict. Reference [1] describes one such instance on the PowerPC > architecture. > > Link: https://lore.kernel.org/all/20251016142831.144515-1-sourabhjain@linux.ibm.com/ [1] > > 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: > > v4 -> v5: > https://lore.kernel.org/all/20251114152550.ac2dd5e23542f09c62defec7@linux-foundation.org/ > - Splitted patch from the above patch series. > - Code to create kexec node under /sys/kernel is added, eariler it was > done in [02/05] of the above patch series. > > v5 -> v6: > - Add Crash CMA Range sysfs interface under /sys/kernel > > Note: > This patch is dependent on the below patch: > https://lore.kernel.org/all/20251117035153.1199665-1-sourabhjain@linux.ibm.com/ > > --- > .../ABI/testing/sysfs-kernel-kexec-kdump | 10 +++++++++ > kernel/ksysfs.c | 21 +++++++++++++++++++ > 2 files changed, 31 insertions(+) Acked-by: Baoquan He > > diff --git a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump > index 96b24565b68e..f6089e38de5f 100644 > --- a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump > +++ b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump > @@ -41,3 +41,13 @@ 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/ksysfs.c b/kernel/ksysfs.c > index eefb67d9883c..0ff2179bc603 100644 > --- a/kernel/ksysfs.c > +++ b/kernel/ksysfs.c > @@ -135,6 +135,24 @@ static ssize_t kexec_crash_loaded_show(struct kobject *kobj, > } > KERNEL_ATTR_RO(kexec_crash_loaded); > > +#ifdef CONFIG_CRASH_RESERVE > +static ssize_t kexec_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; > +} > +KERNEL_ATTR_RO(kexec_crash_cma_ranges); > +#endif /* CONFIG_CRASH_RESERVE */ > + > static ssize_t kexec_crash_size_show(struct kobject *kobj, > struct kobj_attribute *attr, char *buf) > { > @@ -260,6 +278,9 @@ static struct attribute * kernel_attrs[] = { > #ifdef CONFIG_CRASH_DUMP > &kexec_crash_loaded_attr.attr, > &kexec_crash_size_attr.attr, > +#ifdef CONFIG_CRASH_RESERVE > + &kexec_crash_cma_ranges_attr.attr, > +#endif > #endif > #endif > #ifdef CONFIG_VMCORE_INFO > -- > 2.51.1 >