On Tue, 20 Jun 2023 21:57:17 -0300
André Almeida <andrealmeid@xxxxxxxxxx> wrote:
> Create a new DRM ioctl operation to get the numbers of resets for a
> given context. The numbers reflect just the resets that happened after
> the context was created, and not since the machine was booted.
>
> Create a debugfs interface to make easier to test the API without real
> resets.
>
> Signed-off-by: André Almeida <andrealmeid@xxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_debugfs.c | 2 ++
> drivers/gpu/drm/drm_ioctl.c | 58 +++++++++++++++++++++++++++++++++++
> include/drm/drm_device.h | 3 ++
> include/drm/drm_drv.h | 3 ++
> include/uapi/drm/drm.h | 21 +++++++++++++
> include/uapi/drm/drm_mode.h | 15 +++++++++
> 6 files changed, 102 insertions(+)
...
> diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
> index a87bbbbca2d4..a84559aa0d77 100644
> --- a/include/uapi/drm/drm.h
> +++ b/include/uapi/drm/drm.h
> @@ -1169,6 +1169,27 @@ extern "C" {
> */
> #define DRM_IOCTL_MODE_GETFB2 DRM_IOWR(0xCE, struct drm_mode_fb_cmd2)
>
> +/**
> + * DRM_IOCTL_GET_RESET - Get information about device resets
> + *
> + * This operation requests from the device information about resets. It should
> + * consider only resets that happens after the context is created, therefore,
> + * the counter should be zero during context creation.
> + *
> + * dev_reset_count tells how many resets have happened on this device, and
> + * ctx_reset_count tells how many of such resets were caused by this context.
> + *
> + * Flags can be used to tell if a reset is in progress, and userspace should
> + * wait until it's not in progress anymore to be able to create a new context;
> + * and to tell if the VRAM is considered lost. There's no safe way to clean this
> + * flag so if a context see this flag set, it should be like that until the end
> + * of the context.
Is "this flag" the VRAM_LOST? Or any flag?
Does this mean that not all resets are fatal to the context? Is there
any kind of reset that should not be fatal to a context? All the
rendering APIs seem to assume that any reset is fatal and the context
must be destroyed.
> + */
> +#define DRM_IOCTL_GET_RESET DRM_IOWR(0xCF, struct drm_get_reset)
> +
> +#define DRM_RESET_IN_PROGRESS 0x1
> +#define DRM_RESET_VRAM_LOST 0x2
Ok, so the dmabuf lost is being communicated here, but how would a
userspace process know on which device a dmabuf resides on?
Let's assume process A uses device 1 to draw, exports a dmabuf, sends
it to process B which imports it to device 2. Device 1 resets and loses
VRAM contents. How would process B notice that the dmabuf is lost when
it never touches device 1 itself?
> +
> /*
> * Device specific ioctls should only be in their respective headers
> * The device specific ioctl range is from 0x40 to 0x9f.
> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> index 43691058d28f..c3257bd1af9c 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -1308,6 +1308,21 @@ struct drm_mode_rect {
> __s32 y2;
> };
>
> +/**
> + * struct drm_get_reset - Get information about a DRM device resets
> + * @ctx_id: the context id to be queried about resets
> + * @flags: flags
> + * @dev_reset_count: global counter of resets for a given DRM device
> + * @ctx_reset_count: of all the resets counted by this device, how many were
> + * caused by this context.
> + */
> +struct drm_get_reset {
> + __u32 ctx_id;
> + __u32 flags;
> + __u64 dev_reset_count;
> + __u64 ctx_reset_count;
> +};
> +
> #if defined(__cplusplus)
> }
> #endif
Thanks,
pq
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