LKML Archive on
help / color / mirror / Atom feed
From: Kairui Song <>
Cc: Rahul Lakkireddy <>,
	"David S . Miller" <>,
	Eric Biederman <>,
	Alexey Dobriyan <>,
	Andrew Morton <>,
	Dave Young <>,
	"" <>,
	Bhupesh Sharma <>,
	Kairui Song <>
Subject: [PATCH v2] vmcore: Add a kernel cmdline vmcore_device_dump
Date: Mon, 20 May 2019 14:18:34 +0800	[thread overview]
Message-ID: <> (raw)

Since commit 2724273e8fd0 ('vmcore: add API to collect hardware dump in
second kernel'), drivers is allowed to add device related dump data to
vmcore as they want by using the device dump API. This have a potential
issue, the data is stored in memory, drivers may append too much data
and use too much memory. The vmcore is typically used in a kdump kernel
which runs in a pre-reserved small chunk of memory. So as a result it
will make kdump unusable at all due to OOM issues.

So introduce new vmcore_device_dump= kernel parameter, and disable
device dump by default. User can enable it only if device dump data is
required for debugging, and have the chance to increase the kdump
reserved memory accordingly before device dump fails kdump.

Signed-off-by: Kairui Song <>
 Update from V1:
  - Use bool parameter to turn it on/off instead of letting user give
    the size limit. Size of device dump is hard to determine.

 Documentation/admin-guide/kernel-parameters.txt | 15 +++++++++++++++
 fs/proc/vmcore.c                                | 13 +++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 43176340c73d..2d48e39fd080 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5062,6 +5062,21 @@
 			decrease the size and leave more room for directly
 			mapped kernel RAM.
+	vmcore_device_dump=
+			[VMCORE]
+			Format: {"off" | "on"}
+			this parameter allows enable or disable device dump
+			for vmcore.
+			Device dump allows drivers to append dump data to
+			vmcore so you can collect driver specified debug info.
+			Note that the drivers could append the data without
+			any limit, and the data is stored in memory, this may
+			bring a significant memory stress. If you want to turn
+			on this option, make sure you have reserved enough memory
+			with crashkernel= parameter.
+			default: off
 	vmcp_cma=nn[MG]	[KNL,S390]
 			Sets the memory size reserved for contiguous memory
 			allocations for the vmcp device driver.
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 3fe90443c1bb..d1b608b0efad 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -53,6 +53,8 @@ static struct proc_dir_entry *proc_vmcore;
 /* Device Dump list and mutex to synchronize access to list */
 static LIST_HEAD(vmcoredd_list);
 static DEFINE_MUTEX(vmcoredd_mutex);
+static bool vmcoredd_enabled;
 /* Device Dump Size */
@@ -1451,6 +1453,11 @@ int vmcore_add_device_dump(struct vmcoredd_data *data)
 	size_t data_size;
 	int ret;
+	if (!vmcoredd_enabled) {
+		pr_err_once("Device dump is disabled\n");
+		return -EINVAL;
+	}
 	if (!data || !strlen(data->dump_name) ||
 	    !data->vmcoredd_callback || !data->size)
 		return -EINVAL;
@@ -1502,6 +1509,12 @@ int vmcore_add_device_dump(struct vmcoredd_data *data)
 	return ret;
+static int __init vmcoredd_parse_cmdline(char *arg)
+	return kstrtobool(arg, &vmcoredd_enabled);
+__setup("vmcore_device_dump=", vmcoredd_parse_cmdline);
 /* Free all dumps in vmcore device dump list */

             reply	other threads:[~2019-05-20  6:19 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-20  6:18 Kairui Song [this message]
2019-05-22  5:38 ` Dave Young
2019-05-23 11:04   ` Kairui Song
2019-05-22 18:44 ` Bhupesh Sharma
2019-05-23 11:04   ` Kairui Song

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \ \
    --subject='Re: [PATCH v2] vmcore: Add a kernel cmdline vmcore_device_dump' \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).