Re: [PATCH 3/3] drm/i915: FB backing gem obj should reside in LMEM

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 26/09/2019 10:14, Ramalingam C wrote:
> On 2019-09-26 at 09:53:03 +0100, Tvrtko Ursulin wrote:
>>
>> On 26/09/2019 06:21, Ramalingam C wrote:
>>> If Local memory is supported by hardware, we want framebuffer backing
>>> gem objects out of local memory.
>>>
>>> If local memory is supported and gem object if not from local memory we
>>> migrate the obj into local memory. And once framebuffer is created we
>>> block the migration of the associated object out of local memory.
>>>
>>> This is developed on top of v3 LMEM series
>>> https://patchwork.freedesktop.org/series/56683/
>>>
>>> cc: Matthew Auld <matthew.auld@intel.com>
>>> Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
>>> ---
>>>    drivers/gpu/drm/i915/display/intel_display.c | 25 +++++++++
>>>    drivers/gpu/drm/i915/gem/i915_gem_object.c   | 58 ++++++++++++--------
>>>    drivers/gpu/drm/i915/gem/i915_gem_object.h   |  3 +
>>>    3 files changed, 62 insertions(+), 24 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
>>> index 1cc74844d3ea..d1921a317066 100644
>>> --- a/drivers/gpu/drm/i915/display/intel_display.c
>>> +++ b/drivers/gpu/drm/i915/display/intel_display.c
>>> @@ -56,6 +56,8 @@
>>>    #include "display/intel_tv.h"
>>>    #include "display/intel_vdsc.h"
>>> +#include "gem/i915_gem_object.h"
>>> +
>>>    #include "i915_drv.h"
>>>    #include "i915_trace.h"
>>>    #include "intel_acpi.h"
>>> @@ -15496,6 +15498,10 @@ static void intel_setup_outputs(struct drm_i915_private *dev_priv)
>>>    static void intel_user_framebuffer_destroy(struct drm_framebuffer *fb)
>>>    {
>>>    	struct intel_framebuffer *intel_fb = to_intel_framebuffer(fb);
>>> +	struct drm_i915_private *dev_priv = to_i915(fb->dev);
>>> +
>>> +	/* removing the FB memory region restriction on obj, if any */
>>> +	intel_fb->front_buffer->obj = INTEL_INFO(dev_priv)->memory_regions;
>>
>> Is this right, assigning bitmask to something called obj?
> Oops. wanted to assign into the obj->memory_regions. Thanks for
> catching it.
> 
>>
>>>    	drm_framebuffer_cleanup(fb);
>>>    	intel_frontbuffer_put(intel_fb->frontbuffer);
>>> @@ -15543,11 +15549,26 @@ static int intel_framebuffer_init(struct intel_framebuffer *intel_fb,
>>>    {
>>>    	struct drm_i915_private *dev_priv = to_i915(obj->base.dev);
>>>    	struct drm_framebuffer *fb = &intel_fb->base;
>>> +	u32 *region_map;
>>>    	u32 max_stride;
>>>    	unsigned int tiling, stride;
>>>    	int ret = -EINVAL;
>>>    	int i;
>>> +	/* GEM Obj for frame buffer is expected to be in LMEM. */
>>> +	if (HAS_LMEM(dev_priv))
>>> +		if (obj->mm.region->type != INTEL_LMEM) {
>>> +			region_map = &intel_region_map[INTEL_MEMORY_LMEM];
>>> +			ret = i915_gem_object_mem_region_migrate(dev_priv, obj,
>>> +								 region_map,
>>> +								 1);
>>> +			if (ret) {
>>> +				DRM_ERROR("FB migration to LMEM Failed(%d)\n",
>>> +					  ret);
>>
>> Probably should be just debug level since it is imaginably user triggerable
>> and not really an error for the kernel as such.
> 
> Sure.
>>
>>> +				return ret;
>>> +			}
>>> +		}
>>> +
>>>    	intel_fb->frontbuffer = intel_frontbuffer_get(obj);
>>>    	if (!intel_fb->frontbuffer)
>>>    		return -ENOMEM;
>>> @@ -15666,6 +15687,10 @@ static int intel_framebuffer_init(struct intel_framebuffer *intel_fb,
>>>    		goto err;
>>>    	}
>>> +	/* Blocking the migration of gem obj out of LMEM */
>>> +	if (HAS_LMEM(dev_priv))
>>> +		obj->memory_regions = REGION_LMEM;
>>> +
>>>    	return 0;
>>>    err:
>>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c
>>> index e6f8426dedff..65b47054130b 100644
>>> --- a/drivers/gpu/drm/i915/gem/i915_gem_object.c
>>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c
>>> @@ -501,30 +501,11 @@ __region_id(u32 region)
>>>    	return INTEL_MEMORY_UKNOWN;
>>>    }
>>> -static int i915_gem_object_region_select(struct drm_i915_private *dev_priv,
>>> -					 struct drm_i915_gem_object_param *args,
>>> -					 struct drm_file *file,
>>> -					 struct drm_i915_gem_object *obj)
>>> +int i915_gem_object_mem_region_migrate(struct drm_i915_private *dev_priv,
>>> +				       struct drm_i915_gem_object *obj,
>>> +				       u32 *uregions, u32 region_count)
>>>    {
>>>    	struct intel_context *ce = dev_priv->engine[BCS0]->kernel_context;
>>> -	u32 __user *uregions = u64_to_user_ptr(args->data);
>>> -	u32 uregions_copy[INTEL_MEMORY_UKNOWN];
>>> -	int i, ret;
>>> -
>>> -	if (args->size > INTEL_MEMORY_UKNOWN)
>>> -		return -EINVAL;
>>> -
>>> -	memset(uregions_copy, 0, sizeof(uregions_copy));
>>> -	for (i = 0; i < args->size; i++) {
>>> -		u32 region;
>>> -
>>> -		ret = get_user(region, uregions);
>>> -		if (ret)
>>> -			return ret;
>>> -
>>> -		uregions_copy[i] = region;
>>> -		++uregions;
>>> -	}
>>>    	mutex_lock(&dev_priv->drm.struct_mutex);
>>>    	ret = i915_gem_object_prepare_move(obj);
>>> @@ -533,8 +514,8 @@ static int i915_gem_object_region_select(struct drm_i915_private *dev_priv,
>>>    	        goto err;
>>>    	}
>>> -	for (i = 0; i < args->size; i++) {
>>> -		u32 region = uregions_copy[i];
>>> +	for (i = 0; i < region_count; i++) {
>>> +		u32 region = uregions[i];
>>>    		enum intel_region_id id = __region_id(region);
>>>    		if (!(obj->memory_region & region)) {
>>> @@ -576,6 +557,35 @@ static int i915_gem_object_region_select(struct drm_i915_private *dev_priv,
>>>    	return ret;
>>>    }
>>> +static int i915_gem_object_region_select(struct drm_i915_private *dev_priv,
>>> +					 struct drm_i915_gem_object_param *args,
>>> +					 struct drm_file *file,
>>> +					 struct drm_i915_gem_object *obj)
>>> +{
>>> +	struct intel_context *ce = dev_priv->engine[BCS0]->kernel_context;
>>> +	u32 __user *uregions = u64_to_user_ptr(args->data);
>>> +	u32 uregions_copy[INTEL_MEMORY_UKNOWN];
>>> +	int i, ret;
>>> +
>>> +	if (args->size > INTEL_MEMORY_UKNOWN)
>>> +		return -EINVAL;
>>> +
>>> +	memset(uregions_copy, 0, sizeof(uregions_copy));
>>> +	for (i = 0; i < args->size; i++) {
>>> +		u32 region;
>>> +
>>> +		ret = get_user(region, uregions);
>>> +		if (ret)
>>> +			return ret;
>>> +
>>> +		uregions_copy[i] = region;
>>> +		++uregions;
>>> +	}
>>
>> I do understand this is old code (not yours) but I fail to penetrate why is
>> this a loop and not copy_from_user?
> What i understood is, list of possible regions_maps are passed here. and
> they are reading it one after another.

Yes, and making a kernel copy. AFAICS i == uregions at the end of the 
loop and args->size worth of u32 has been copied. Equivalent to 
copy_from_user(uregions_copy, uregions, args->size * sizeof(u32)). Maybe 
I am blind yet again..

>>
>>> +
>>> +	return i915_gem_object_mem_region_migrate(dev_priv, obj, uregions_copy,
>>> +						  args->size);
>>> +}
>>> +
>>>    int i915_gem_object_setparam_ioctl(struct drm_device *dev, void *data,
>>>    				   struct drm_file *file)
>>>    {
>>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
>>> index a7c073aeb777..d09a9c741b41 100644
>>> --- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
>>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
>>> @@ -47,6 +47,9 @@ int i915_gem_object_migrate(struct drm_i915_gem_object *obj,
>>>    			    enum intel_region_id id);
>>>    void i915_gem_flush_free_objects(struct drm_i915_private *i915);
>>> +int i915_gem_object_mem_region_migrate(struct drm_i915_private *dev_priv,
>>> +				       struct drm_i915_gem_object *obj,
>>> +				       u32 *uregions, u32 region_count);
>>>    void __i915_gem_object_reset_page_iter(struct drm_i915_gem_object *obj);
>>>
>>
>> General approach looks feasible to me, but I'll leave guys directly involved
>> with local memory to call it.
>>
>> Another my comment/question would be - do we have a hook when objects are
>> released/disassociated from the framebuffer and should we restore the
>> allowed memory region mask to default at that point?
> at present I am doing this at intel_user_framebuffer_destroy. Not sure
> if we have any better place for this.

Oh it's at the top of the patch. My bad for forgetting about it. The 
region copying loop caused some head scratching and I forgot. :)

Regards,

Tvrtko
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