Messages in this thread Patch in this message | | | Subject | Re: [PATCH v2] vmcore: Add a kernel cmdline vmcore_device_dump | From | Bhupesh Sharma <> | Date | Thu, 23 May 2019 00:14:39 +0530 |
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On 05/20/2019 11:48 AM, 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@redhat.com> > --- > 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"} > + If CONFIG_PROC_VMCORE_DEVICE_DUMP is set, > + this parameter allows enable or disable device dump > + for vmcore.
We can add a simpler description here, something like: Depends on CONFIG_PROC_VMCORE_DEVICE_DUMP
> + 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
... and massage the rest of text accordingly.
Better to also modify the help text for 'PROC_VMCORE_DEVICE_DUMP' config option defined in 'fs/proc/Kconfig'. Something like:
config PROC_VMCORE_DEVICE_DUMP bool "Device Hardware/Firmware Log Collection" <..snip..> If you say Y here, the collected device dumps will be added as ELF notes to /proc/vmcore.
If this option is selected, device dump collection can still be disabled by passing vmcore_device_dump=off to the kernel.
See config INTEL_IOMMU_DEFAULT_ON in 'drivers/iommu/Kconfig' as an example.
> 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 */ >
Thanks, Bhupesh
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