On 05/24/19 at 02:29pm, 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 V2:
> - Improve related docs
>
> 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 | 14 ++++++++++++++
> fs/proc/Kconfig | 6 ++++--
> fs/proc/vmcore.c | 13 +++++++++++++
> 3 files changed, 31 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 138f6664b2e2..3706ad9e1d97 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -5078,6 +5078,20 @@
> decrease the size and leave more room for directly
> mapped kernel RAM.
>
> + vmcore_device_dump= [KNL,KDUMP]
> + Format: {"off" | "on"}
> + Depends on CONFIG_PROC_VMCORE_DEVICE_DUMP.
> + This parameter allows enable or disable device dump
> + for vmcore on kernel start-up.
> + 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/Kconfig b/fs/proc/Kconfig
> index 817c02b13b1d..1a7a38976bb0 100644
> --- a/fs/proc/Kconfig
> +++ b/fs/proc/Kconfig
> @@ -56,8 +56,10 @@ config PROC_VMCORE_DEVICE_DUMP
> recovery kernel's initramfs to collect its underlying device
> snapshot.
>
> - If you say Y here, the collected device dumps will be added
> - as ELF notes to /proc/vmcore.
> + If you say Y here, a new kernel parameter 'vmcore_device_dump'
> + will be available. You can then enable device dump by passing
"a new kernel parameter 'vmcore_device_dump' will be available" is not
necessary, "new" is a not a clear word. I suggest to remove this
sentence.
s/You can then/You can
Otherwise:
Acked-by: Dave Young <dyoung@xxxxxxxxxx>
> + 'vmcore_device_dump=on' to kernel, the collected device dumps
> + will be added as ELF notes to /proc/vmcore.
>
> config PROC_SYSCTL
> bool "Sysctl support (/proc/sys)" if EXPERT
> 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
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