GPU reset is a very important piece of our infrastructure.
Unfortunately we only really test it by actually hanging the gpu,
which often has bad side-effects for the entire system. And the gpu
hang handling code is one of the rather complicated pieces of code we
have, consisting of
- hang detection
- error capture
- actual gpu reset
- reset of all the gem bookkeeping
- reinitialition of the entire gpu
This patch adds a debugfs to selectively stopping rings by ceasing to
update the hw tail pointer. This way we can exercise the gpu hang code
under controlled conditions without a dying gpu taking down the entire
systems.
Patch motivated by me forgetting to properly reinitialize ppgtt after
a gpu reset.
Signed-Off-by: Daniel Vetter <daniel.vet...@ffwll.ch>
---
drivers/gpu/drm/i915/i915_debugfs.c | 63 +++++++++++++++++++++++++++++++
drivers/gpu/drm/i915/i915_drv.c | 3 +
drivers/gpu/drm/i915/i915_drv.h | 2 +
drivers/gpu/drm/i915/intel_ringbuffer.c | 4 ++
4 files changed, 72 insertions(+), 0 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c
b/drivers/gpu/drm/i915/i915_debugfs.c
index 8476441..9821a3b 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -1392,6 +1392,64 @@ static const struct file_operations i915_wedged_fops = {
};
static ssize_t
+i915_ring_stop_read(struct file *filp,
+ char __user *ubuf,
+ size_t max,
+ loff_t *ppos)
+{
+ struct drm_device *dev = filp->private_data;
+ drm_i915_private_t *dev_priv = dev->dev_private;
+ char buf[80];
+ int len;
+
+ len = snprintf(buf, sizeof(buf),
+ "%d\n", dev_priv->stop_rings);
+
+ if (len > sizeof(buf))
+ len = sizeof(buf);
+
+ return simple_read_from_buffer(ubuf, max, ppos, buf, len);
+}
+
+static ssize_t
+i915_ring_stop_write(struct file *filp,
+ const char __user *ubuf,
+ size_t cnt,
+ loff_t *ppos)
+{
+ struct drm_device *dev = filp->private_data;
+ struct drm_i915_private *dev_priv = dev->dev_private;
+ char buf[20];
+ int val = 0;
+
+ if (cnt > 0) {
+ if (cnt > sizeof(buf) - 1)
+ return -EINVAL;
+
+ if (copy_from_user(buf, ubuf, cnt))
+ return -EFAULT;
+ buf[cnt] = 0;
+
+ val = simple_strtoul(buf, NULL, 0);
+ }
+
+ DRM_DEBUG_DRIVER("Stopping rings %u\n", val);
+
+ mutex_lock(&dev->struct_mutex);
+ dev_priv->stop_rings = val;
+ mutex_unlock(&dev->struct_mutex);
+
+ return cnt;
+}
+
+static const struct file_operations i915_ring_stop_fops = {
+ .owner = THIS_MODULE,
+ .open = i915_debugfs_common_open,
+ .read = i915_ring_stop_read,
+ .write = i915_ring_stop_write,
+ .llseek = default_llseek,
+};
+static ssize_t
i915_max_freq_read(struct file *filp,
char __user *ubuf,
size_t max,
@@ -1691,6 +1749,11 @@ int i915_debugfs_init(struct drm_minor *minor)
&i915_cache_sharing_fops);
if (ret)
return ret;
+ ret = i915_debugfs_create(minor->debugfs_root, minor,
+ "i915_ring_stop",
+ &i915_ring_stop_fops);
+ if (ret)
+ return ret;
return drm_debugfs_create_files(i915_debugfs_list,
I915_DEBUGFS_ENTRIES,
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 548e04b..566cc1e 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -611,6 +611,9 @@ int i915_reset(struct drm_device *dev, u8 flags)
if (!mutex_trylock(&dev->struct_mutex))
return -EBUSY;
+ printk("reenabling rings\n");
+ dev_priv->stop_rings = 0;
+
i915_gem_reset(dev);
ret = -ENODEV;
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index bd98fb3..503ae8c 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -330,6 +330,8 @@ typedef struct drm_i915_private {
uint32_t last_instdone;
uint32_t last_instdone1;
+ unsigned int stop_rings;
+
unsigned long cfb_size;
unsigned int cfb_fb;
enum plane cfb_plane;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c
b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 3c30dba..ef7a1ca 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1179,7 +1179,11 @@ int intel_ring_begin(struct intel_ring_buffer *ring,
void intel_ring_advance(struct intel_ring_buffer *ring)
{
+ struct drm_i915_private *dev_priv = ring->dev->dev_private;
+
ring->tail &= ring->size - 1;
+ if (dev_priv->stop_rings & intel_ring_flag(ring))
+ return;
ring->write_tail(ring, ring->tail);
}
--
1.7.6.4
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