Re: [Intel-gfx] [PATCH v6] drm/i915: Individualize fences before adding to dma_resv obj

["Das, Nirmoy" <nirmoy.das@intel.com>]

On 5/26/2022 11:27 AM, Matthew Auld wrote:
> On 25/05/2022 10:59, Nirmoy Das wrote:
>> _i915_vma_move_to_active() can receive > 1 fences for
>> multiple batch buffers submission. Because dma_resv_add_fence()
>> can only accept one fence at a time, change _i915_vma_move_to_active()
>> to be aware of multiple fences so that it can add individual
>> fences to the dma resv object.
>>
>> v6: fix multi-line comment.
>> v5: remove double fence reservation for batch VMAs.
>> v4: Reserve fences for composite_fence on multi-batch contexts and
>>      also reserve fence slots to composite_fence for each VMAs.
>> v3: dma_resv_reserve_fences is not cumulative so pass num_fences.
>> v2: make sure to reserve enough fence slots before adding.
>>
>> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/5614
>> Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
> Reviewed-by: Matthew Auld <matthew.auld@intel.com>
>
> Do we need Fixes: ?


We can add:

Fixes: 544460c33821 ("drm/i915: Multi-BB execbuf")


Regards,

Nirmoy


>
>> ---
>>   .../gpu/drm/i915/gem/i915_gem_execbuffer.c    |  3 +-
>>   drivers/gpu/drm/i915/i915_vma.c               | 48 +++++++++++--------
>>   2 files changed, 30 insertions(+), 21 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c 
>> b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
>> index b279588c0672..8880d38d36b6 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
>> @@ -1010,7 +1010,8 @@ static int eb_validate_vmas(struct 
>> i915_execbuffer *eb)
>>               }
>>           }
>>   -        err = dma_resv_reserve_fences(vma->obj->base.resv, 1);
>> +        /* Reserve enough slots to accommodate composite fences */
>> +        err = dma_resv_reserve_fences(vma->obj->base.resv, 
>> eb->num_batches);
>>           if (err)
>>               return err;
>>   diff --git a/drivers/gpu/drm/i915/i915_vma.c 
>> b/drivers/gpu/drm/i915/i915_vma.c
>> index 4f6db539571a..0bffb70b3c5f 100644
>> --- a/drivers/gpu/drm/i915/i915_vma.c
>> +++ b/drivers/gpu/drm/i915/i915_vma.c
>> @@ -23,6 +23,7 @@
>>    */
>>     #include <linux/sched/mm.h>
>> +#include <linux/dma-fence-array.h>
>>   #include <drm/drm_gem.h>
>>     #include "display/intel_frontbuffer.h"
>> @@ -1823,6 +1824,21 @@ int _i915_vma_move_to_active(struct i915_vma 
>> *vma,
>>       if (unlikely(err))
>>           return err;
>>   +    /*
>> +     * Reserve fences slot early to prevent an allocation after 
>> preparing
>> +     * the workload and associating fences with dma_resv.
>> +     */
>> +    if (fence && !(flags & __EXEC_OBJECT_NO_RESERVE)) {
>> +        struct dma_fence *curr;
>> +        int idx;
>> +
>> +        dma_fence_array_for_each(curr, idx, fence)
>> +            ;
>> +        err = dma_resv_reserve_fences(vma->obj->base.resv, idx);
>> +        if (unlikely(err))
>> +            return err;
>> +    }
>> +
>>       if (flags & EXEC_OBJECT_WRITE) {
>>           struct intel_frontbuffer *front;
>>   @@ -1832,31 +1848,23 @@ int _i915_vma_move_to_active(struct 
>> i915_vma *vma,
>>                   i915_active_add_request(&front->write, rq);
>>               intel_frontbuffer_put(front);
>>           }
>> +    }
>>   -        if (!(flags & __EXEC_OBJECT_NO_RESERVE)) {
>> -            err = dma_resv_reserve_fences(vma->obj->base.resv, 1);
>> -            if (unlikely(err))
>> -                return err;
>> -        }
>> +    if (fence) {
>> +        struct dma_fence *curr;
>> +        enum dma_resv_usage usage;
>> +        int idx;
>>   -        if (fence) {
>> -            dma_resv_add_fence(vma->obj->base.resv, fence,
>> -                       DMA_RESV_USAGE_WRITE);
>> +        obj->read_domains = 0;
>> +        if (flags & EXEC_OBJECT_WRITE) {
>> +            usage = DMA_RESV_USAGE_WRITE;
>>               obj->write_domain = I915_GEM_DOMAIN_RENDER;
>> -            obj->read_domains = 0;
>> -        }
>> -    } else {
>> -        if (!(flags & __EXEC_OBJECT_NO_RESERVE)) {
>> -            err = dma_resv_reserve_fences(vma->obj->base.resv, 1);
>> -            if (unlikely(err))
>> -                return err;
>> +        } else {
>> +            usage = DMA_RESV_USAGE_READ;
>>           }
>>   -        if (fence) {
>> -            dma_resv_add_fence(vma->obj->base.resv, fence,
>> -                       DMA_RESV_USAGE_READ);
>> -            obj->write_domain = 0;
>> -        }
>> +        dma_fence_array_for_each(curr, idx, fence)
>> +            dma_resv_add_fence(vma->obj->base.resv, curr, usage);
>>       }
>>         if (flags & EXEC_OBJECT_NEEDS_FENCE && vma->fence)