[PATCH v7 1/5] drm: Introduce device wedged event
Christian König
christian.koenig at amd.com
Thu Oct 17 07:59:10 UTC 2024
Am 17.10.24 um 04:47 schrieb Raag Jadav:
> On Mon, Sep 30, 2024 at 01:08:41PM +0530, Raag Jadav wrote:
>> Introduce device wedged event, which will notify userspace of wedged
>> (hanged/unusable) state of the DRM device through a uevent. This is
>> useful especially in cases where the device is no longer operating as
>> expected even after a hardware reset and has become unrecoverable from
>> driver context.
Well introduce is probably the wrong wording since i915 already has that
and amdgpu looked into it but never upstreamed the support.
I would rather say standardize.
>>
>> Purpose of this implementation is to provide drivers a generic way to
>> recover with the help of userspace intervention. Different drivers may
>> have different ideas of a "wedged device" depending on their hardware
>> implementation, and hence the vendor agnostic nature of the event.
>> It is up to the drivers to decide when they see the need for recovery
>> and how they want to recover from the available methods.
>>
>> Current implementation defines three recovery methods, out of which,
>> drivers can choose to support any one or multiple of them. Preferred
>> recovery method will be sent in the uevent environment as WEDGED=<method>.
>> Userspace consumers (sysadmin) can define udev rules to parse this event
>> and take respective action to recover the device.
>>
>> =============== ==================================
>> Recovery method Consumer expectations
>> =============== ==================================
>> rebind unbind + rebind driver
>> bus-reset unbind + reset bus device + rebind
>> reboot reboot system
>> =============== ==================================
Well that sounds like userspace would need to be involved in recovery.
That in turn is a complete no-go since we at least need to signal all
dma_fences to unblock the kernel. In other words things like bus reset
needs to happen inside the kernel and *not* in userspace.
What we can do is to signal to userspace: Hey a bus reset of device X
happened, maybe restart container, daemon, whatever service which was
using this device.
Regards,
Christian.
>>
>> v4: s/drm_dev_wedged/drm_dev_wedged_event
>> Use drm_info() (Jani)
>> Kernel doc adjustment (Aravind)
>> v5: Send recovery method with uevent (Lina)
>> v6: Access wedge_recovery_opts[] using helper function (Jani)
>> Use snprintf() (Jani)
>> v7: Convert recovery helpers into regular functions (Andy, Jani)
>> Aesthetic adjustments (Andy)
>> Handle invalid method cases
>>
>> Signed-off-by: Raag Jadav <raag.jadav at intel.com>
>> ---
> Cc'ing amd, collabora and others as I found semi-related work at
>
> https://lore.kernel.org/dri-devel/20230627132323.115440-1-andrealmeid@igalia.com/
> https://lore.kernel.org/amd-gfx/20240725150055.1991893-1-alexander.deucher@amd.com/
> https://lore.kernel.org/dri-devel/20241011225906.3789965-3-adrian.larumbe@collabora.com/
> https://lore.kernel.org/amd-gfx/CAAxE2A5v_RkZ9ex4=7jiBSKVb22_1FAj0AANBcmKtETt5c3gVA@mail.gmail.com/
>
>
> Please share feedback about usefulness and adoption of this.
> Improvements are welcome.
>
> Raag
>
>> drivers/gpu/drm/drm_drv.c | 77 +++++++++++++++++++++++++++++++++++++++
>> include/drm/drm_device.h | 23 ++++++++++++
>> include/drm/drm_drv.h | 3 ++
>> 3 files changed, 103 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
>> index ac30b0ec9d93..cfe9600da2ee 100644
>> --- a/drivers/gpu/drm/drm_drv.c
>> +++ b/drivers/gpu/drm/drm_drv.c
>> @@ -26,6 +26,8 @@
>> * DEALINGS IN THE SOFTWARE.
>> */
>>
>> +#include <linux/array_size.h>
>> +#include <linux/build_bug.h>
>> #include <linux/debugfs.h>
>> #include <linux/fs.h>
>> #include <linux/module.h>
>> @@ -33,6 +35,7 @@
>> #include <linux/mount.h>
>> #include <linux/pseudo_fs.h>
>> #include <linux/slab.h>
>> +#include <linux/sprintf.h>
>> #include <linux/srcu.h>
>> #include <linux/xarray.h>
>>
>> @@ -70,6 +73,42 @@ static struct dentry *drm_debugfs_root;
>>
>> DEFINE_STATIC_SRCU(drm_unplug_srcu);
>>
>> +/*
>> + * Available recovery methods for wedged device. To be sent along with device
>> + * wedged uevent.
>> + */
>> +static const char *const drm_wedge_recovery_opts[] = {
>> + [DRM_WEDGE_RECOVERY_REBIND] = "rebind",
>> + [DRM_WEDGE_RECOVERY_BUS_RESET] = "bus-reset",
>> + [DRM_WEDGE_RECOVERY_REBOOT] = "reboot",
>> +};
>> +
>> +static bool drm_wedge_recovery_is_valid(enum drm_wedge_recovery method)
>> +{
>> + static_assert(ARRAY_SIZE(drm_wedge_recovery_opts) == DRM_WEDGE_RECOVERY_MAX);
>> +
>> + return method >= DRM_WEDGE_RECOVERY_REBIND && method < DRM_WEDGE_RECOVERY_MAX;
>> +}
>> +
>> +/**
>> + * drm_wedge_recovery_name - provide wedge recovery name
>> + * @method: method to be used for recovery
>> + *
>> + * This validates wedge recovery @method against the available ones in
>> + * drm_wedge_recovery_opts[] and provides respective recovery name in string
>> + * format if found valid.
>> + *
>> + * Returns: pointer to const recovery string on success, NULL otherwise.
>> + */
>> +const char *drm_wedge_recovery_name(enum drm_wedge_recovery method)
>> +{
>> + if (drm_wedge_recovery_is_valid(method))
>> + return drm_wedge_recovery_opts[method];
>> +
>> + return NULL;
>> +}
>> +EXPORT_SYMBOL(drm_wedge_recovery_name);
>> +
>> /*
>> * DRM Minors
>> * A DRM device can provide several char-dev interfaces on the DRM-Major. Each
>> @@ -497,6 +536,44 @@ void drm_dev_unplug(struct drm_device *dev)
>> }
>> EXPORT_SYMBOL(drm_dev_unplug);
>>
>> +/**
>> + * drm_dev_wedged_event - generate a device wedged uevent
>> + * @dev: DRM device
>> + * @method: method to be used for recovery
>> + *
>> + * This generates a device wedged uevent for the DRM device specified by @dev.
>> + * Recovery @method from drm_wedge_recovery_opts[] (if supprted by the device)
>> + * is sent in the uevent environment as WEDGED=<method>, on the basis of which,
>> + * userspace may take respective action to recover the device.
>> + *
>> + * Returns: 0 on success, or negative error code otherwise.
>> + */
>> +int drm_dev_wedged_event(struct drm_device *dev, enum drm_wedge_recovery method)
>> +{
>> + /* Event string length up to 16+ characters with available methods */
>> + char event_string[32] = {};
>> + char *envp[] = { event_string, NULL };
>> + const char *recovery;
>> +
>> + recovery = drm_wedge_recovery_name(method);
>> + if (!recovery) {
>> + drm_err(dev, "device wedged, invalid recovery method %d\n", method);
>> + return -EINVAL;
>> + }
>> +
>> + if (!test_bit(method, &dev->wedge_recovery)) {
>> + drm_err(dev, "device wedged, %s based recovery not supported\n",
>> + drm_wedge_recovery_name(method));
>> + return -EOPNOTSUPP;
>> + }
>> +
>> + snprintf(event_string, sizeof(event_string), "WEDGED=%s", recovery);
>> +
>> + drm_info(dev, "device wedged, generating uevent for %s based recovery\n", recovery);
>> + return kobject_uevent_env(&dev->primary->kdev->kobj, KOBJ_CHANGE, envp);
>> +}
>> +EXPORT_SYMBOL(drm_dev_wedged_event);
>> +
>> /*
>> * DRM internal mount
>> * We want to be able to allocate our own "struct address_space" to control
>> diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
>> index c91f87b5242d..fed6f20e52fb 100644
>> --- a/include/drm/drm_device.h
>> +++ b/include/drm/drm_device.h
>> @@ -40,6 +40,26 @@ enum switch_power_state {
>> DRM_SWITCH_POWER_DYNAMIC_OFF = 3,
>> };
>>
>> +/**
>> + * enum drm_wedge_recovery - Recovery method for wedged device in order of
>> + * severity. To be set as bit fields in drm_device.wedge_recovery variable.
>> + * Drivers can choose to support any one or multiple of them depending on
>> + * their needs.
>> + */
>> +enum drm_wedge_recovery {
>> + /** @DRM_WEDGE_RECOVERY_REBIND: unbind + rebind driver */
>> + DRM_WEDGE_RECOVERY_REBIND,
>> +
>> + /** @DRM_WEDGE_RECOVERY_BUS_RESET: unbind + reset bus device + rebind */
>> + DRM_WEDGE_RECOVERY_BUS_RESET,
>> +
>> + /** @DRM_WEDGE_RECOVERY_REBOOT: reboot system */
>> + DRM_WEDGE_RECOVERY_REBOOT,
>> +
>> + /** @DRM_WEDGE_RECOVERY_MAX: for bounds checking, do not use */
>> + DRM_WEDGE_RECOVERY_MAX
>> +};
>> +
>> /**
>> * struct drm_device - DRM device structure
>> *
>> @@ -317,6 +337,9 @@ struct drm_device {
>> * Root directory for debugfs files.
>> */
>> struct dentry *debugfs_root;
>> +
>> + /** @wedge_recovery: Supported recovery methods for wedged device */
>> + unsigned long wedge_recovery;
>> };
>>
>> #endif
>> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
>> index 02ea4e3248fd..d8dbc77010b0 100644
>> --- a/include/drm/drm_drv.h
>> +++ b/include/drm/drm_drv.h
>> @@ -462,6 +462,9 @@ bool drm_dev_enter(struct drm_device *dev, int *idx);
>> void drm_dev_exit(int idx);
>> void drm_dev_unplug(struct drm_device *dev);
>>
>> +const char *drm_wedge_recovery_name(enum drm_wedge_recovery method);
>> +int drm_dev_wedged_event(struct drm_device *dev, enum drm_wedge_recovery method);
>> +
>> /**
>> * drm_dev_is_unplugged - is a DRM device unplugged
>> * @dev: DRM device
>> --
>> 2.34.1
>>
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