From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 B879C2DE707 for ; Tue, 11 Nov 2025 01:15:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762823746; cv=none; b=G7yul4lwPKvhfKteijTpRONUmcud+R2sBPXCi1sCMPhnqjTaUcZkSNFiuwPTwUfrl8lV/f0Kz5RkMUmCgMlS4DYodkAZRQd3rWcM5o/tMKkMpd8ZDtvS8B3zRX9tVQbxAahWdRm2R8qG1aUzw9Wge7xAZV6bxifFYUsLjbCEHlc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762823746; c=relaxed/simple; bh=UHwWdL8yMFiyzuIXi3IpIyFuianaoUXyCkSZKyhpm4I=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=S32/LBWB9ghdEKaFWqJmd9M/kLp+wD22AkSi3vTxPvwojkCT8ShB/UsliWZOLxv/T7KBnqUneCzKmho9RTWjGdc1fHbS9Wf6kehFC57EgVhVnuSEEkXwjQyuWEp8vg/bNgV6no1l9Xpt3iIL0vxdGL0sxtaY3FSvVaiZBP3b6dE= 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=MCn1GxXV; arc=none smtp.client-ip=170.10.129.124 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="MCn1GxXV" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1762823743; 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=lFuNMW6QorcHfFRhlUpmszpPvplH5exAgJCXldoReDA=; b=MCn1GxXVoBSAWRqCthTJkV58iCJlrwDtPwY72f74v4aXDjpeA45clsZ5M7apvklzowLJ40 uu1LHvIx5JzT00sIcutIMOpuR+ABXmKuqdRfoexOXyL19I5veo0gj+U1Um4y1UAPdT3gG4 4mQgso9drOBDl55W15YJLlyHJqDHMIQ= 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-213-dxEhYB_gNzeGhPkRGAx9IQ-1; Mon, 10 Nov 2025 20:15:40 -0500 X-MC-Unique: dxEhYB_gNzeGhPkRGAx9IQ-1 X-Mimecast-MFC-AGG-ID: dxEhYB_gNzeGhPkRGAx9IQ_1762823738 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 5A91B19560A2; Tue, 11 Nov 2025 01:15:37 +0000 (UTC) Received: from localhost (unknown [10.72.112.59]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 2CF2F30044E0; Tue, 11 Nov 2025 01:15:33 +0000 (UTC) Date: Tue, 11 Nov 2025 09:15:23 +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> <09c4c181-eb4b-43ea-a439-04b83f4c20ba@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: <09c4c181-eb4b-43ea-a439-04b83f4c20ba@linux.ibm.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 On 11/10/25 at 02:09pm, Sourabh Jain wrote: > > > On 10/11/25 12:38, Baoquan he wrote: > > 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. > > Handling conflict is challenging. Hence we don't export crashk_res and > crashk_low_res to iomem on powerpc. Checkout [1] > > And I think conflicts can occur regardless of the order in which System RAM > and > Crash CMA ranges are added to iomem. > > [1] https://lore.kernel.org/all/20251016142831.144515-1-sourabhjain@linux.ibm.com/ Then I would suggest you add this reason and the link into patch log to keep a record. One day people may post patch to 'optimize' this. > > > > > > 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 > > > >