[PATCH v2 1/2] drm/amdgpu: Detect if amdgpu in IOMMU direct map mode

[Alex Deucher]

On Thu, Dec 9, 2021 at 12:02 PM Philip Yang <Philip.Yang at amd.com> wrote:
>
> If host and amdgpu IOMMU is not enabled or IOMMU is pass through mode,
> set adev->ram_is_direct_mapped flag which will be used to optimize
> memory usage for multi GPU mappings.
>
> Signed-off-by: Philip Yang <Philip.Yang at amd.com>

Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu.h        |  2 ++
>  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 19 +++++++++++++++++++
>  2 files changed, 21 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index 54c882a6b433..0ec19c83a203 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -1097,6 +1097,8 @@ struct amdgpu_device {
>
>         struct amdgpu_reset_control     *reset_cntl;
>         uint32_t                        ip_versions[MAX_HWIP][HWIP_MAX_INSTANCE];
> +
> +       bool                            ram_is_direct_mapped;
>  };
>
>  static inline struct amdgpu_device *drm_to_adev(struct drm_device *ddev)
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index ce9bdef185c0..3318d92de8eb 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -30,6 +30,7 @@
>  #include <linux/module.h>
>  #include <linux/console.h>
>  #include <linux/slab.h>
> +#include <linux/iommu.h>
>
>  #include <drm/drm_atomic_helper.h>
>  #include <drm/drm_probe_helper.h>
> @@ -3381,6 +3382,22 @@ static int amdgpu_device_get_job_timeout_settings(struct amdgpu_device *adev)
>         return ret;
>  }
>
> +/**
> + * amdgpu_device_check_iommu_direct_map - check if RAM direct mapped to GPU
> + *
> + * @adev: amdgpu_device pointer
> + *
> + * RAM direct mapped to GPU if IOMMU is not enabled or is pass through mode
> + */
> +static void amdgpu_device_check_iommu_direct_map(struct amdgpu_device *adev)
> +{
> +       struct iommu_domain *domain;
> +
> +       domain = iommu_get_domain_for_dev(adev->dev);
> +       if (!domain || domain->type == IOMMU_DOMAIN_IDENTITY)
> +               adev->ram_is_direct_mapped = true;
> +}
> +
>  static const struct attribute *amdgpu_dev_attributes[] = {
>         &dev_attr_product_name.attr,
>         &dev_attr_product_number.attr,
> @@ -3784,6 +3801,8 @@ int amdgpu_device_init(struct amdgpu_device *adev,
>                 queue_delayed_work(system_wq, &mgpu_info.delayed_reset_work,
>                                    msecs_to_jiffies(AMDGPU_RESUME_MS));
>
> +       amdgpu_device_check_iommu_direct_map(adev);
> +
>         return 0;
>
>  release_ras_con:
> --
> 2.17.1
>