RE: [PATCH v2 1/4] iommu/vt-d: Block force-snoop domain attaching if no SC support

[Tian, Kevin]

> From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Sent: Thursday, May 5, 2022 9:07 AM
> 
> In the attach_dev callback of the default domain ops, if the domain has
> been set force_snooping, but the iommu hardware of the device does not
> support SC(Snoop Control) capability, the callback should block it and
> return a corresponding error code.
> 
> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>

> ---
>  drivers/iommu/intel/iommu.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index cf43e8f9091b..d68f5bbf3e93 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -4354,6 +4354,9 @@ static int prepare_domain_attach_device(struct
> iommu_domain *domain,
>  	if (!iommu)
>  		return -ENODEV;
> 
> +	if (dmar_domain->force_snooping && !ecap_sc_support(iommu-
> >ecap))
> +		return -EOPNOTSUPP;
> +
>  	/* check if this iommu agaw is sufficient for max mapped address */
>  	addr_width = agaw_to_width(iommu->agaw);
>  	if (addr_width > cap_mgaw(iommu->cap))
> --
> 2.25.1