Re: [PATCH 4/4] drm/i915: l3 parity sysfs interface

[Ben Widawsky <ben@bwidawsk.net>]

On Fri, 27 Jul 2012 04:19:10 +0000
"Zhang, Xiong Y" <xiong.y.zhang@intel.com> wrote:

>    
>    Who will monitor this sysfs interface, 2D driver or 3D driver or other application ?
>    Now, I don't find any user of this sysfs interface in 2D driver or 3D driver.
> 
> thanks

The notification is meant to be received through a udev event. What user
space should do at that point has been somewhat up to discussion thus
far. In order to correct the issues, a neutral root third party should
receieve the event and program the sysfs entry with the remap
information (possibly also force a GPU reset through debugfs).

In the ideal case, I think we should have GPU clients somehow register
that they want to be notified by such an event, maybe a signal based
mechanism, so they can dump all of their buffers and start over. That
should allow us to not force the GPU reset.

So far, we've not had any GPU clients that care enough abuot a faulty
cacheline to use such an interface. It was really provided as a
gpgpu/compute shader type of feature.


> 
> -----Original Message-----
> From: intel-gfx-bounces+xiong.y.zhang=intel.com@lists.freedesktop.org [mailto:intel-gfx-bounces+xiong.y.zhang=intel.com@lists.freedesktop.org] On Behalf Of Ben Widawsky
> Sent: Saturday, May 26, 2012 7:56 AM
> To: intel-gfx@lists.freedesktop.org
> Cc: Ben Widawsky
> Subject: [Intel-gfx] [PATCH 4/4] drm/i915: l3 parity sysfs interface
> 
> Dumb binary interfaces which allow root-only updates of the cache remapping registers. As mentioned in a previous patch, software using this interface needs to know about HW limits, and other programming considerations as the kernel interface does no checking for these things on the root-only interface.
> 
> v1: Drop extra posting reads (Chris)
> Return negative values in the sysfs interfaces on errors (Chris)
> 
> v2: Return -EINVAL for offset % 4 (Jesse) Move schizo userspace check out (Jesse) Cleaner sysfs item initializers (Daniel)
> 
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> ---
>  drivers/gpu/drm/i915/i915_sysfs.c |  121 ++++++++++++++++++++++++++++++++++++-
>  1 file changed, 119 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_sysfs.c b/drivers/gpu/drm/i915/i915_sysfs.c
> index 79f8344..c201327 100644
> --- a/drivers/gpu/drm/i915/i915_sysfs.c
> +++ b/drivers/gpu/drm/i915/i915_sysfs.c
> @@ -29,6 +29,7 @@
>  #include <linux/module.h>
>  #include <linux/stat.h>
>  #include <linux/sysfs.h>
> +#include "intel_drv.h"
>  #include "i915_drv.h"
>  
>  static u32 calc_residency(struct drm_device *dev, const u32 reg) @@ -92,20 +93,136 @@ static struct attribute_group rc6_attr_group = {
>  	.attrs =  rc6_attrs
>  };
>  
> +static int l3_access_valid(struct drm_device *dev, loff_t offset) {
> +	if (!IS_IVYBRIDGE(dev))
> +		return -EPERM;
> +
> +	if (offset % 4 != 0)
> +		return -EINVAL;
> +
> +	if (offset >= GEN7_L3LOG_SIZE)
> +		return -ENXIO;
> +
> +	return 0;
> +}
> +
> +static ssize_t
> +i915_l3_read(struct file *filp, struct kobject *kobj,
> +	     struct bin_attribute *attr, char *buf,
> +	     loff_t offset, size_t count)
> +{
> +	struct device *dev = container_of(kobj, struct device, kobj);
> +	struct drm_minor *dminor = container_of(dev, struct drm_minor, kdev);
> +	struct drm_device *drm_dev = dminor->dev;
> +	struct drm_i915_private *dev_priv = drm_dev->dev_private;
> +	uint32_t misccpctl;
> +	int i, ret;
> +
> +	ret = l3_access_valid(drm_dev, offset);
> +	if (ret)
> +		return ret;
> +
> +	ret = i915_mutex_lock_interruptible(drm_dev);
> +	if (ret)
> +		return ret;
> +
> +	misccpctl = I915_READ(GEN7_MISCCPCTL);
> +	I915_WRITE(GEN7_MISCCPCTL, misccpctl & ~GEN7_DOP_CLOCK_GATE_ENABLE);
> +
> +	for (i = offset; count >= 4 && i < GEN7_L3LOG_SIZE; i += 4, count -= 4)
> +		*((uint32_t *)(&buf[i])) = I915_READ(GEN7_L3LOG_BASE + i);
> +
> +	I915_WRITE(GEN7_MISCCPCTL, misccpctl);
> +
> +	mutex_unlock(&drm_dev->struct_mutex);
> +
> +	return i - offset;
> +}
> +
> +static ssize_t
> +i915_l3_write(struct file *filp, struct kobject *kobj,
> +	      struct bin_attribute *attr, char *buf,
> +	      loff_t offset, size_t count)
> +{
> +	struct device *dev = container_of(kobj, struct device, kobj);
> +	struct drm_minor *dminor = container_of(dev, struct drm_minor, kdev);
> +	struct drm_device *drm_dev = dminor->dev;
> +	struct drm_i915_private *dev_priv = drm_dev->dev_private;
> +	u32 *temp = NULL; /* Just here to make handling failures easy */
> +	int ret;
> +
> +	ret = l3_access_valid(drm_dev, offset);
> +	if (ret)
> +		return ret;
> +
> +	ret = i915_mutex_lock_interruptible(drm_dev);
> +	if (ret)
> +		return ret;
> +
> +	if (!dev_priv->mm.l3_remap_info) {
> +		temp = kzalloc(GEN7_L3LOG_SIZE, GFP_KERNEL);
> +		if (!temp) {
> +			mutex_unlock(&drm_dev->struct_mutex);
> +			return -ENOMEM;
> +		}
> +	}
> +
> +	ret = i915_gpu_idle(drm_dev);
> +	if (ret) {
> +		kfree(temp);
> +		mutex_unlock(&drm_dev->struct_mutex);
> +		return ret;
> +	}
> +
> +	/* TODO: Ideally we really want a GPU reset here to make sure errors
> +	 * aren't propagated. Since I cannot find a stable way to reset the GPU
> +	 * at this point it is left as a TODO.
> +	*/
> +	if (temp)
> +		dev_priv->mm.l3_remap_info = temp;
> +
> +	memcpy(dev_priv->mm.l3_remap_info + (offset/4),
> +	       buf + (offset/4),
> +	       count);
> +
> +	i915_gem_l3_remap(drm_dev);
> +
> +	mutex_unlock(&drm_dev->struct_mutex);
> +
> +	return count;
> +}
> +
> +static struct bin_attribute dpf_attrs = {
> +	.attr = {.name = "l3_parity", .mode = (S_IRUSR | S_IWUSR)},
> +	.size = GEN7_L3LOG_SIZE,
> +	.read = i915_l3_read,
> +	.write = i915_l3_write,
> +	.mmap = NULL
> +};
> +
>  void i915_setup_sysfs(struct drm_device *dev)  {
>  	int ret;
>  
> -	/* ILK doesn't have any residency information */
> +	/* ILK and below don't yet have relevant sysfs files */
>  	if (INTEL_INFO(dev)->gen < 6)
>  		return;
>  
>  	ret = sysfs_merge_group(&dev->primary->kdev.kobj, &rc6_attr_group);
>  	if (ret)
> -		DRM_ERROR("sysfs setup failed\n");
> +		DRM_ERROR("RC6 residency sysfs setup failed\n");
> +
> +	if (!IS_IVYBRIDGE(dev))
> +		return;
> +
> +	ret = device_create_bin_file(&dev->primary->kdev, &dpf_attrs);
> +	if (ret)
> +		DRM_ERROR("l3 parity sysfs setup failed\n");
>  }
>  
>  void i915_teardown_sysfs(struct drm_device *dev)  {
> +	device_remove_bin_file(&dev->primary->kdev,  &dpf_attrs);
>  	sysfs_unmerge_group(&dev->primary->kdev.kobj, &rc6_attr_group);  }
> --
> 1.7.10.2
> 
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-- 
Ben Widawsky, Intel Open Source Technology Center