Re: [PATCH] iommu/amd: Enhance def_domain_type to handle untrusted device

[Baolu Lu <baolu.lu@linux.intel.com>]

On 2024/4/19 19:47, Vasant Hegde wrote:
> Previously, IOMMU core layer was forcing IOMMU_DOMAIN_DMA domain for
> untrusted device. This always took precedence over driver's
> def_domain_type(). Commit 59ddce4418da ("iommu: Reorganize
> iommu_get_default_domain_type() to respect def_domain_type()") changed
> the behaviour. Current code calls def_domain_type() but if it doesn't
> return IOMMU_DOMAIN_DMA for untrusted device it throws error. This
> results in IOMMU group (and potentially IOMMU itself) in undetermined
> sstate.
> 
> This patch adds untrusted check in AMD IOMMU driver code. So that it
> lets eGPUs behind Thunderbolt work again.
> 
> Fine tuning amd_iommu_def_domain_type() will be done later.
> 
> Reported-by: Eric Wagner<ewagner12@gmail.com>
> Link:https://lore.kernel.org/linux-iommu/CAHudX3zLH6CsRmLE-yb+gRjhh-v4bU5_1jW_xCcxOo_oUUZKYg@mail.gmail.com
> Fixes: 59ddce4418da ("iommu: Reorganize iommu_get_default_domain_type() to respect def_domain_type()")
> Cc: Robin Murphy<robin.murphy@arm.com>
> Cc: Jason Gunthorpe<jgg@ziepe.ca>
> Cc:stable@kernel.org  # v6.7+
> Signed-off-by: Vasant Hegde<vasant.hegde@amd.com>
> ---
> @Eric,
>    Can you please test this patch?
> 
> -Vasant
> 
>   drivers/iommu/amd/iommu.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
> index e692217fcb28..e405714640b0 100644
> --- a/drivers/iommu/amd/iommu.c
> +++ b/drivers/iommu/amd/iommu.c
> @@ -2754,6 +2754,10 @@ static int amd_iommu_def_domain_type(struct device *dev)
>   	if (!dev_data)
>   		return 0;
>   
> +	/* Always use DMA domain for untrusted device */
> +	if (to_pci_dev(dev)->untrusted)
> +		return IOMMU_DOMAIN_DMA;

Are you sure that dev always represents a pci device? If not, perhaps
here it needs a dev_is_pci() check?

Best regards,
baolu