Re: [PATCH 2/6] iommu/vt-d: Implement hw_info for iommu capability query

[Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx>]

On 2/9/2023 12:16 PM, Yi Liu wrote:
> From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
>
> To support nested translation in the userspace, it should check the
> underlying hardware information for the capabilities.
>
> Add intel_iommu_hw_info() to report cap_reg and ecap_reg information.
>
> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
> Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> Signed-off-by: Yi Sun <yi.y.sun@xxxxxxxxxxxxxxx>
> ---
>   drivers/iommu/intel/iommu.c  | 19 +++++++++++++++++++
>   drivers/iommu/intel/iommu.h  |  1 +
>   include/uapi/linux/iommufd.h | 21 +++++++++++++++++++++
>   3 files changed, 41 insertions(+)
>
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 59df7e42fd53..929f600cc350 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -4760,8 +4760,26 @@ static void intel_iommu_remove_dev_pasid(struct device *dev, ioasid_t pasid)
>   	intel_pasid_tear_down_entry(iommu, dev, pasid, false);
>   }
>   
> +static void *intel_iommu_hw_info(struct device *dev, u32 *length)
> +{
> +	struct device_domain_info *info = dev_iommu_priv_get(dev);
> +	struct intel_iommu *iommu = info->iommu;
> +	struct iommu_device_info_vtd *vtd;
> +
> +	vtd = kzalloc(sizeof(*vtd), GFP_KERNEL);
> +	if (!vtd)
> +		return ERR_PTR(-ENOMEM);
> +
> +	vtd->cap_reg = iommu->cap;
> +	vtd->ecap_reg = iommu->ecap;
> +	*length = sizeof(*vtd);
> +
> +	return vtd;
> +}
> +
>   const struct iommu_ops intel_iommu_ops = {
>   	.capable		= intel_iommu_capable,
> +	.hw_info		= intel_iommu_hw_info,
>   	.domain_alloc		= intel_iommu_domain_alloc,
>   	.probe_device		= intel_iommu_probe_device,
>   	.probe_finalize		= intel_iommu_probe_finalize,
> @@ -4774,6 +4792,7 @@ const struct iommu_ops intel_iommu_ops = {
>   	.def_domain_type	= device_def_domain_type,
>   	.remove_dev_pasid	= intel_iommu_remove_dev_pasid,
>   	.pgsize_bitmap		= SZ_4K,
> +	.driver_type		= IOMMU_DEVICE_DATA_INTEL_VTD,
>   #ifdef CONFIG_INTEL_IOMMU_SVM
>   	.page_response		= intel_svm_page_response,
>   #endif
> diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h
> index 06e61e474856..2e70265d4ceb 100644
> --- a/drivers/iommu/intel/iommu.h
> +++ b/drivers/iommu/intel/iommu.h
> @@ -22,6 +22,7 @@
>   #include <linux/ioasid.h>
>   #include <linux/bitfield.h>
>   #include <linux/xarray.h>
> +#include <uapi/linux/iommufd.h>
>   
>   #include <asm/cacheflush.h>
>   #include <asm/iommu.h>
> diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
> index 2309edb55028..fda75c8450ee 100644
> --- a/include/uapi/linux/iommufd.h
> +++ b/include/uapi/linux/iommufd.h
> @@ -347,7 +347,28 @@ struct iommu_vfio_ioas {
>   
>   /**
>    * enum iommu_device_data_type - IOMMU hardware Data types
> + * @IOMMU_DEVICE_DATA_INTEL_VTD: Intel VT-d iommu data type
>    */
>   enum iommu_device_data_type {
> +	IOMMU_DEVICE_DATA_INTEL_VTD = 1,
> +};
> +
> +/**
> + * struct iommu_device_info_vtd - Intel VT-d device info
> + *
> + * @flags: Must be set to 0

Could you add more description about the usage of flags here?


> + * @__reserved: Must be 0
> + * @cap_reg: Value of Intel VT-d capability register defined in chapter
> + *	     11.4.2 of Intel VT-d spec.
> + * @ecap_reg: Value of Intel VT-d capability register defined in chapter
> + *	     11.4.3 of Intel VT-d spec.
> + *
> + * Intel hardware iommu capability.
> + */
> +struct iommu_device_info_vtd {
> +	__u32 flags;
> +	__u32 __reserved;
> +	__aligned_u64 cap_reg;
> +	__aligned_u64 ecap_reg;
>   };
>   #endif