Re: [PATCH v3 7/8] drm/panfrost: Implement generic DRM object RSS reporting function

[Adrián Larumbe]

On 06.09.2023 10:01, Boris Brezillon wrote:
>On Tue,  5 Sep 2023 19:45:23 +0100
>Adrián Larumbe <adrian.larumbe@xxxxxxxxxxxxx> wrote:
>
>> BO's RSS is updated every time new pages are allocated on demand and mapped
>> for the object at GPU page fault's IRQ handler, but only for heap buffers.
>> The reason this is unnecessary for non-heap buffers is that they are mapped
>> onto the GPU's VA space and backed by physical memory in their entirety at
>> BO creation time.
>> 
>> This calculation is unnecessary for imported PRIME objects, since heap
>> buffers cannot be exported by our driver, and the actual BO RSS size is the
>> one reported in its attached dmabuf structure.
>> 
>> Signed-off-by: Adrián Larumbe <adrian.larumbe@xxxxxxxxxxxxx>
>> ---
>>  drivers/gpu/drm/panfrost/panfrost_gem.c | 14 ++++++++++++++
>>  drivers/gpu/drm/panfrost/panfrost_gem.h |  5 +++++
>>  drivers/gpu/drm/panfrost/panfrost_mmu.c | 12 ++++++++----
>>  3 files changed, 27 insertions(+), 4 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
>> index 7d8f83d20539..cb92c0ed7615 100644
>> --- a/drivers/gpu/drm/panfrost/panfrost_gem.c
>> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
>> @@ -208,6 +208,19 @@ static enum drm_gem_object_status panfrost_gem_status(struct drm_gem_object *obj
>>  	return res;
>>  }
>>  
>> +static size_t panfrost_gem_rss(struct drm_gem_object *obj)
>> +{
>> +	struct panfrost_gem_object *bo = to_panfrost_bo(obj);
>> +
>> +	if (bo->is_heap)
>> +		return bo->heap_rss_size;
>> +	else if (bo->base.pages) {
>> +		WARN_ON(bo->heap_rss_size);
>> +		return bo->base.base.size;
>> +	} else
>> +		return 0;
>
>Nit: please add brackets on all conditional blocks, even if only the
>second one needs it.
>
>> +}
>> +
>>  static const struct drm_gem_object_funcs panfrost_gem_funcs = {
>>  	.free = panfrost_gem_free_object,
>>  	.open = panfrost_gem_open,
>> @@ -220,6 +233,7 @@ static const struct drm_gem_object_funcs panfrost_gem_funcs = {
>>  	.vunmap = drm_gem_shmem_object_vunmap,
>>  	.mmap = drm_gem_shmem_object_mmap,
>>  	.status = panfrost_gem_status,
>> +	.rss = panfrost_gem_rss,
>>  	.vm_ops = &drm_gem_shmem_vm_ops,
>>  };
>>  
>> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.h b/drivers/gpu/drm/panfrost/panfrost_gem.h
>> index ad2877eeeccd..13c0a8149c3a 100644
>> --- a/drivers/gpu/drm/panfrost/panfrost_gem.h
>> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.h
>> @@ -36,6 +36,11 @@ struct panfrost_gem_object {
>>  	 */
>>  	atomic_t gpu_usecount;
>>  
>> +	/*
>> +	 * Object chunk size currently mapped onto physical memory
>> +	 */
>> +	size_t heap_rss_size;
>> +
>>  	bool noexec		:1;
>>  	bool is_heap		:1;
>>  };
>> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
>> index d54d4e7b2195..67c206124781 100644
>> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
>> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
>> @@ -285,17 +285,19 @@ static void panfrost_mmu_flush_range(struct panfrost_device *pfdev,
>>  	pm_runtime_put_autosuspend(pfdev->dev);
>>  }
>>  
>> -static int mmu_map_sg(struct panfrost_device *pfdev, struct panfrost_mmu *mmu,
>> +static size_t mmu_map_sg(struct panfrost_device *pfdev, struct panfrost_mmu *mmu,
>>  		      u64 iova, int prot, struct sg_table *sgt)
>>  {
>>  	unsigned int count;
>>  	struct scatterlist *sgl;
>>  	struct io_pgtable_ops *ops = mmu->pgtbl_ops;
>>  	u64 start_iova = iova;
>> +	size_t total = 0;
>>  
>>  	for_each_sgtable_dma_sg(sgt, sgl, count) {
>>  		unsigned long paddr = sg_dma_address(sgl);
>>  		size_t len = sg_dma_len(sgl);
>> +		total += len;
>>  
>>  		dev_dbg(pfdev->dev, "map: as=%d, iova=%llx, paddr=%lx, len=%zx", mmu->as, iova, paddr, len);
>>  
>> @@ -315,7 +317,7 @@ static int mmu_map_sg(struct panfrost_device *pfdev, struct panfrost_mmu *mmu,
>>  
>>  	panfrost_mmu_flush_range(pfdev, mmu, start_iova, iova - start_iova);
>>  
>> -	return 0;
>> +	return total;
>>  }
>>  
>>  int panfrost_mmu_map(struct panfrost_gem_mapping *mapping)
>> @@ -447,6 +449,7 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
>>  	pgoff_t page_offset;
>>  	struct sg_table *sgt;
>>  	struct page **pages;
>> +	size_t mapped_size;
>>  
>>  	bomapping = addr_to_mapping(pfdev, as, addr);
>>  	if (!bomapping)
>> @@ -518,10 +521,11 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
>>  	if (ret)
>>  		goto err_map;
>>  
>> -	mmu_map_sg(pfdev, bomapping->mmu, addr,
>> -		   IOMMU_WRITE | IOMMU_READ | IOMMU_NOEXEC, sgt);
>> +	mapped_size = mmu_map_sg(pfdev, bomapping->mmu, addr,
>> +				 IOMMU_WRITE | IOMMU_READ | IOMMU_NOEXEC, sgt);
>>  
>>  	bomapping->active = true;
>> +	bo->heap_rss_size += mapped_size;
>
>The alloc-on-fault granularity is set static (2MB), so no need to
>make mmu_map_sg() return the mapped size, we can just do += SZ_2M if
>things worked.

At the moment mmu_map_sg is treated as though it always succeeds in mapping the
page. Would it be alright if I changed it so that we take into account the
unlikely case that ops->map_pages might fail?
Something like this: https://gitlab.collabora.com/-/snippets/323

>>  
>>  	dev_dbg(pfdev->dev, "mapped page fault @ AS%d %llx", as, addr);
>>