RE: [PATCH v1 3/8] vfio/type1: Report PASID alloc/free support to userspace

[Tian, Kevin]

> From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> Sent: Sunday, March 22, 2020 8:32 PM
> 
> From: Liu Yi L <yi.l.liu@xxxxxxxxx>
> 
> This patch reports PASID alloc/free availability to userspace (e.g. QEMU)
> thus userspace could do a pre-check before utilizing this feature.
> 
> Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
> CC: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>
> Cc: Eric Auger <eric.auger@xxxxxxxxxx>
> Cc: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> Signed-off-by: Liu Yi L <yi.l.liu@xxxxxxxxx>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 28 ++++++++++++++++++++++++++++
>  include/uapi/linux/vfio.h       |  8 ++++++++
>  2 files changed, 36 insertions(+)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c
> b/drivers/vfio/vfio_iommu_type1.c
> index e40afc0..ddd1ffe 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -2234,6 +2234,30 @@ static int vfio_iommu_type1_pasid_free(struct
> vfio_iommu *iommu,
>  	return ret;
>  }
> 
> +static int vfio_iommu_info_add_nesting_cap(struct vfio_iommu *iommu,
> +					 struct vfio_info_cap *caps)
> +{
> +	struct vfio_info_cap_header *header;
> +	struct vfio_iommu_type1_info_cap_nesting *nesting_cap;
> +
> +	header = vfio_info_cap_add(caps, sizeof(*nesting_cap),
> +				   VFIO_IOMMU_TYPE1_INFO_CAP_NESTING,
> 1);
> +	if (IS_ERR(header))
> +		return PTR_ERR(header);
> +
> +	nesting_cap = container_of(header,
> +				struct vfio_iommu_type1_info_cap_nesting,
> +				header);
> +
> +	nesting_cap->nesting_capabilities = 0;
> +	if (iommu->nesting) {

Is it good to report a nesting cap when iommu->nesting is disabled? I suppose
the check should move before vfio_info_cap_add...

> +		/* nesting iommu type supports PASID requests (alloc/free)
> */
> +		nesting_cap->nesting_capabilities |=
> VFIO_IOMMU_PASID_REQS;

VFIO_IOMMU_CAP_PASID_REQ? to avoid confusion with ioctl cmd
VFIO_IOMMU_PASID_REQUEST...

> +	}
> +
> +	return 0;
> +}
> +
>  static long vfio_iommu_type1_ioctl(void *iommu_data,
>  				   unsigned int cmd, unsigned long arg)
>  {
> @@ -2283,6 +2307,10 @@ static long vfio_iommu_type1_ioctl(void
> *iommu_data,
>  		if (ret)
>  			return ret;
> 
> +		ret = vfio_iommu_info_add_nesting_cap(iommu, &caps);
> +		if (ret)
> +			return ret;
> +
>  		if (caps.size) {
>  			info.flags |= VFIO_IOMMU_INFO_CAPS;
> 
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 298ac80..8837219 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -748,6 +748,14 @@ struct vfio_iommu_type1_info_cap_iova_range {
>  	struct	vfio_iova_range iova_ranges[];
>  };
> 
> +#define VFIO_IOMMU_TYPE1_INFO_CAP_NESTING  2
> +
> +struct vfio_iommu_type1_info_cap_nesting {
> +	struct	vfio_info_cap_header header;
> +#define VFIO_IOMMU_PASID_REQS	(1 << 0)
> +	__u32	nesting_capabilities;
> +};
> +
>  #define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12)
> 
>  /**
> --
> 2.7.4