Re: [PATCH 1/2] drm/amdkfd: Add SVM range mapped_to_gpu flag

[Felix Kuehling <felix.kuehling@xxxxxxx>]

Am 2022-04-19 um 20:47 schrieb Philip Yang:
> To avoid unnecessary unmap SVM range from GPUs if range is not mapped on
> GPUs when migrating the range. This flag will also be used to flush TLB
> when updating the existing mapping on GPUs.
>
> It is protected by prange->migrate_mutex and mmap read lock in MMU
> notifier callback.
>
> Signed-off-by: Philip Yang <Philip.Yang@xxxxxxx>

Reviewed-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>


> ---
>   drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 17 ++++++++++++++++-
>   drivers/gpu/drm/amd/amdkfd/kfd_svm.h |  1 +
>   2 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> index 5afe216cf099..6be1695f3a09 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> @@ -951,6 +951,7 @@ svm_range_split_adjust(struct svm_range *new, struct svm_range *old,
>   	new->prefetch_loc = old->prefetch_loc;
>   	new->actual_loc = old->actual_loc;
>   	new->granularity = old->granularity;
> +	new->mapped_to_gpu = old->mapped_to_gpu;
>   	bitmap_copy(new->bitmap_access, old->bitmap_access, MAX_GPU_INSTANCE);
>   	bitmap_copy(new->bitmap_aip, old->bitmap_aip, MAX_GPU_INSTANCE);
>   
> @@ -1204,6 +1205,17 @@ svm_range_unmap_from_gpus(struct svm_range *prange, unsigned long start,
>   	uint32_t gpuidx;
>   	int r = 0;
>   
> +	if (!prange->mapped_to_gpu) {
> +		pr_debug("prange 0x%p [0x%lx 0x%lx] not mapped to GPU\n",
> +			 prange, prange->start, prange->last);
> +		return 0;
> +	}
> +
> +	if (prange->start == start && prange->last == last) {
> +		pr_debug("unmap svms 0x%p prange 0x%p\n", prange->svms, prange);
> +		prange->mapped_to_gpu = false;
> +	}
> +
>   	bitmap_or(bitmap, prange->bitmap_access, prange->bitmap_aip,
>   		  MAX_GPU_INSTANCE);
>   	p = container_of(prange->svms, struct kfd_process, svms);
> @@ -1590,8 +1602,10 @@ static int svm_range_validate_and_map(struct mm_struct *mm,
>   		addr = next;
>   	}
>   
> -	if (addr == end)
> +	if (addr == end) {
>   		prange->validated_once = true;
> +		prange->mapped_to_gpu = true;
> +	}
>   
>   unreserve_out:
>   	svm_range_unreserve_bos(&ctx);
> @@ -1822,6 +1836,7 @@ static struct svm_range *svm_range_clone(struct svm_range *old)
>   	new->prefetch_loc = old->prefetch_loc;
>   	new->actual_loc = old->actual_loc;
>   	new->granularity = old->granularity;
> +	new->mapped_to_gpu = old->mapped_to_gpu;
>   	bitmap_copy(new->bitmap_access, old->bitmap_access, MAX_GPU_INSTANCE);
>   	bitmap_copy(new->bitmap_aip, old->bitmap_aip, MAX_GPU_INSTANCE);
>   
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.h b/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
> index 66c77f00ac3e..2d54147b4dda 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
> @@ -133,6 +133,7 @@ struct svm_range {
>   	DECLARE_BITMAP(bitmap_access, MAX_GPU_INSTANCE);
>   	DECLARE_BITMAP(bitmap_aip, MAX_GPU_INSTANCE);
>   	bool				validated_once;
> +	bool				mapped_to_gpu;
>   };
>   
>   static inline void svm_range_lock(struct svm_range *prange)