On Wed, May 22, 2019 at 1:38 PM Dave Young <dyoung@xxxxxxxxxx> wrote:
>
> On 05/20/19 at 02:18pm, Kairui Song wrote:
> > 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 <kasong@xxxxxxxxxx>
> > ---
> > 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]
>
> It looks better to have above two line merged in one line, also use
> [KNL, KDUMP] will be better.
>
> > + Format: {"off" | "on"}
> > + If CONFIG_PROC_VMCORE_DEVICE_DUMP is set,
> > + 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;
> > #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */
> >
> > /* 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;
> > }
> > EXPORT_SYMBOL(vmcore_add_device_dump);
> > +
> > +static int __init vmcoredd_parse_cmdline(char *arg)
> > +{
> > + return kstrtobool(arg, &vmcoredd_enabled);
> > +}
> > +__setup("vmcore_device_dump=", vmcoredd_parse_cmdline);
> > #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */
> >
> > /* Free all dumps in vmcore device dump list */
> > --
> > 2.21.0
> >
>
> Thanks
> Dave
Good suggestion, I'll update in V3.
--
Best Regards,
Kairui Song
_______________________________________________
kexec mailing list
kexec@xxxxxxxxxxxxxxxxxxx
http://lists.infradead.org/mailman/listinfo/kexec
