Re: [Intel-gfx] [PATCH] drm/i915/uc: use io memcpy functions for device memory copy

[Siva Mullati <siva.mullati@intel.com>]

LGTM

Acked-by: Siva Mullati <siva.mullati@intel.com>

On 06/04/22 14:48, Vivekanandan, Balasubramani wrote:
> When copying RSA use io memcpy functions if the destination address
> contains a GPU local memory address. Considering even the source
> address can be on local memory, a bounce buffer is used to copy from io
> to io.
> The intention of this patch is to make i915 portable outside x86 mainly
> on ARM64.
>
> Signed-off-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
> ---
>  drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c | 23 +++++++++++++++++++++--
>  1 file changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c b/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c
> index bb864655c495..06d30670e15c 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c
> @@ -589,7 +589,7 @@ static int uc_fw_rsa_data_create(struct intel_uc_fw *uc_fw)
>  	struct intel_gt *gt = __uc_fw_to_gt(uc_fw);
>  	struct i915_vma *vma;
>  	size_t copied;
> -	void *vaddr;
> +	void *vaddr, *bounce;
>  	int err;
>  
>  	err = i915_inject_probe_error(gt->i915, -ENXIO);
> @@ -621,7 +621,26 @@ static int uc_fw_rsa_data_create(struct intel_uc_fw *uc_fw)
>  		goto unpin_out;
>  	}
>  
> -	copied = intel_uc_fw_copy_rsa(uc_fw, vaddr, vma->size);
> +	if (i915_gem_object_is_lmem(vma->obj)) {
> +		/* When vma is allocated from the GPU local memmory, it means
> +		 * the destination address contains an io memory and we need to
> +		 * use memcpy function for io memory for copying, to ensure
> +		 * i915 portability outside x86. It is most likely the RSA will
> +		 * also be on local memory and so the source of copy will also
> +		 * be an io address. Since we cannot directly copy from io to
> +		 * io, we use a bounce buffer to copy.
> +		 */
> +		copied = 0;
> +		bounce = kmalloc(vma->size, GFP_KERNEL);
> +		if (likely(bounce)) {
> +			copied = intel_uc_fw_copy_rsa(uc_fw, bounce, vma->size);
> +			memcpy_toio((void __iomem *)vaddr, bounce, copied);
> +			kfree(bounce);
> +		}
> +	} else {
> +		copied = intel_uc_fw_copy_rsa(uc_fw, vaddr, vma->size);
> +	}
> +
>  	i915_gem_object_unpin_map(vma->obj);
>  
>  	if (copied < uc_fw->rsa_size) {