[PATCH] drm/vmwgfx: Enable DMA mappings with SEV

[Martin Krastev]

On Mon, Apr 8, 2024 at 5:28 AM Zack Rusin <zack.rusin at broadcom.com> wrote:
>
> Enable DMA mappings in vmwgfx after TTM has been fixed in commit
> 3bf3710e3718 ("drm/ttm: Add a generic TTM memcpy move for page-based iomem")
>
> This enables full guest-backed memory support and in particular allows
> usage of screen targets as the presentation mechanism.
>
> Signed-off-by: Zack Rusin <zack.rusin at broadcom.com>
> Reported-by: Ye Li <ye.li at broadcom.com>
> Tested-by: Ye Li <ye.li at broadcom.com>
> Fixes: 3b0d6458c705 ("drm/vmwgfx: Refuse DMA operation when SEV encryption is active")
> Cc: Broadcom internal kernel review list <bcm-kernel-feedback-list at broadcom.com>
> Cc: dri-devel at lists.freedesktop.org
> Cc: <stable at vger.kernel.org> # v6.6+
> ---
>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> index 41ad13e45554..bdad93864b98 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> @@ -667,11 +667,12 @@ static int vmw_dma_select_mode(struct vmw_private *dev_priv)
>                 [vmw_dma_map_populate] = "Caching DMA mappings.",
>                 [vmw_dma_map_bind] = "Giving up DMA mappings early."};
>
> -       /* TTM currently doesn't fully support SEV encryption. */
> -       if (cc_platform_has(CC_ATTR_MEM_ENCRYPT))
> -               return -EINVAL;
> -
> -       if (vmw_force_coherent)
> +       /*
> +        * When running with SEV we always want dma mappings, because
> +        * otherwise ttm tt pool pages will bounce through swiotlb running
> +        * out of available space.
> +        */
> +       if (vmw_force_coherent || cc_platform_has(CC_ATTR_MEM_ENCRYPT))
>                 dev_priv->map_mode = vmw_dma_alloc_coherent;
>         else if (vmw_restrict_iommu)
>                 dev_priv->map_mode = vmw_dma_map_bind;
> --
> 2.40.1


LGTM!

Reviewed-by: Martin Krastev <martin.krastev at broadcom.com>

Regards,
Martin