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Subject: RE: [PATCH 3/3] vfio: Report PASID capability via VFIO_DEVICE_FEATURE
 ioctl
Thread-Topic: [PATCH 3/3] vfio: Report PASID capability via
 VFIO_DEVICE_FEATURE ioctl
Thread-Index: AQHaIPx2EKyfzMrBBEWzcc+IDcJP4bCdkKlg
Date:   Thu, 7 Dec 2023 08:47:48 +0000
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References: <20231127063909.129153-1-yi.l.liu@intel.com>
 <20231127063909.129153-4-yi.l.liu@intel.com>
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> From: Liu, Yi L <yi.l.liu@intel.com>
> Sent: Monday, November 27, 2023 2:39 PM
>=20
> +static int vfio_pci_core_feature_pasid(struct vfio_device *device, u32 f=
lags,
> +				       struct vfio_device_feature_pasid __user
> *arg,
> +				       size_t argsz)
> +{
> +	struct vfio_pci_core_device *vdev =3D
> +		container_of(device, struct vfio_pci_core_device, vdev);
> +	struct vfio_device_feature_pasid pasid =3D { 0 };
> +	struct pci_dev *pdev =3D vdev->pdev;
> +	u32 capabilities =3D 0;
> +	int ret;
> +
> +	/* We do not support SET of the PASID capability */

this line alone is meaningless. Please explain the reason e.g. due to
no PASID capability per VF...

> +	ret =3D vfio_check_feature(flags, argsz, VFIO_DEVICE_FEATURE_GET,
> +				 sizeof(pasid));
> +	if (ret !=3D 1)
> +		return ret;
> +
> +	/*
> +	 * Needs go to PF if the device is VF as VF shares its PF's
> +	 * PASID Capability.
> +	 */

/* VF shares the PASID capability of its PF */

> +	if (pdev->is_virtfn)
> +		pdev =3D pci_physfn(pdev);
> +
> +	if (!pdev->pasid_enabled)
> +		goto out;
> +
> +#ifdef CONFIG_PCI_PASID
> +	pci_read_config_dword(pdev, pdev->pasid_cap + PCI_PASID_CAP,
> +			      &capabilities);
> +#endif

#ifdef is unnecessary. If CONFIG_PCI_PASID is false pdev->pasid_enabled
won't be set anyway.

and it should read from PCI_PASID_CTRL which indicates whether a
capability is actually enabled.

> +/**
> + * Upon VFIO_DEVICE_FEATURE_GET, return the PASID capability for the
> device.
> + * Zero width means no support for PASID.

also mention the encoding of this field according to PCIe spec.

or turn it to a plain number field.

> + */
> +struct vfio_device_feature_pasid {
> +	__u16 capabilities;
> +#define VFIO_DEVICE_PASID_CAP_EXEC	(1 << 0)
> +#define VFIO_DEVICE_PASID_CAP_PRIV	(1 << 1)
> +	__u8 width;
> +	__u8 __reserved;
> +};
> +#define VFIO_DEVICE_FEATURE_PASID 11
> +
>  /* -------- API for Type1 VFIO IOMMU -------- */
>=20
>  /**
> --
> 2.34.1