Re: [RFC PATCH v3 2/4] drm: Create DRM_IOCTL_GET_RESET
From: André Almeida
Date: Wed Jun 21 2023 - 12:35:23 EST
Em 21/06/2023 05:09, Pekka Paalanen escreveu:
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.
I got this flag from the `AMDGPU_CTX_OP_QUERY_STATE2` operation, and
it's used to notify that the reset was fatal for a giving context,
although the idea of non-fatal resets seems to be a bit controversial
for now, so I think it will be better if I leave this flag for latter
improvements of the API.
+ */
+#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