[PATCH rc] gpu: host1x: Do not assume that a NULL domain means no DMA IOMMU

[Diogo Ivo]

Hi all,

On 2/4/25 7:18 PM, Jason Gunthorpe wrote:
> Previously with tegra-smmu, even with CONFIG_IOMMU_DMA, the default domain
> could have been left as NULL. The NULL domain is specially recognized by
> host1x_iommu_attach() as meaning it is not the DMA domain and
> should be replaced with the special shared domain.
> 
> This happened prior to the below commit because tegra-smmu was using the
> NULL domain to mean IDENTITY.
> 
> Now that the domain is properly labled the test in DRM doesn't see NULL.
> Check for IDENTITY as well to enable the special domains.
> 
> This is the same issue and basic fix as seen in
> commit fae6e669cdc5 ("drm/tegra: Do not assume that a NULL domain means no
> DMA IOMMU").
> 
> Fixes: c8cc2655cc6c ("iommu/tegra-smmu: Implement an IDENTITY domain")
> Reported-by: Diogo Ivo <diogo.ivo at tecnico.ulisboa.pt>
> Closes: https://lore.kernel.org/all/c6a6f114-3acd-4d56-a13b-b88978e927dc@tecnico.ulisboa.pt/
> Tested-by: Diogo Ivo <diogo.ivo at tecnico.ulisboa.pt>
> Signed-off-by: Jason Gunthorpe <jgg at nvidia.com>
> ---
>   drivers/gpu/host1x/dev.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/host1x/dev.c b/drivers/gpu/host1x/dev.c
> index 7b1d091f3c090c..5d27662019d28b 100644
> --- a/drivers/gpu/host1x/dev.c
> +++ b/drivers/gpu/host1x/dev.c
> @@ -361,6 +361,10 @@ static bool host1x_wants_iommu(struct host1x *host1x)
>   	return true;
>   }
>   
> +/*
> + * Returns ERR_PTR on failure, NULL if the translation is IDENTITY, otherwise a
> + * valid paging domain.
> + */
>   static struct iommu_domain *host1x_iommu_attach(struct host1x *host)
>   {
>   	struct iommu_domain *domain = iommu_get_domain_for_dev(host->dev);
> @@ -385,6 +389,8 @@ static struct iommu_domain *host1x_iommu_attach(struct host1x *host)
>   	 * Similarly, if host1x is already attached to an IOMMU (via the DMA
>   	 * API), don't try to attach again.
>   	 */
> +	if (domain && domain->type == IOMMU_DOMAIN_IDENTITY)
> +		domain = NULL;
>   	if (!host1x_wants_iommu(host) || domain)
>   		return domain;
>   
> 
> base-commit: 2014c95afecee3e76ca4a56956a936e23283f05b

Any updates on the status of this patch?

Thanks,
Diogo