vfio: Introduce VFIO_DEVICE_FEATURE ioctl and first user

The VFIO_DEVICE_FEATURE ioctl is meant to be a general purpose, device
agnostic ioctl for setting, retrieving, and probing device features.
This implementation provides a 16-bit field for specifying a feature
index, where the data porition of the ioctl is determined by the
semantics for the given feature.  Additional flag bits indicate the
direction and nature of the operation; SET indicates user data is
provided into the device feature, GET indicates the device feature is
written out into user data.  The PROBE flag augments determining
whether the given feature is supported, and if provided, whether the
given operation on the feature is supported.

The first user of this ioctl is for setting the vfio-pci VF token,
where the user provides a shared secret key (UUID) on a SR-IOV PF
device, which users must provide when opening associated VF devices.

Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

1 files changed, 37 insertions, 0 deletions

diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 9e843a147ead..015516bcfaa3 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -707,6 +707,43 @@ struct vfio_device_ioeventfd {
 
 #define VFIO_DEVICE_IOEVENTFD		_IO(VFIO_TYPE, VFIO_BASE + 16)
 
+/**
+ * VFIO_DEVICE_FEATURE - _IORW(VFIO_TYPE, VFIO_BASE + 17,
+ *			       struct vfio_device_feature)
+ *
+ * Get, set, or probe feature data of the device.  The feature is selected
+ * using the FEATURE_MASK portion of the flags field.  Support for a feature
+ * can be probed by setting both the FEATURE_MASK and PROBE bits.  A probe
+ * may optionally include the GET and/or SET bits to determine read vs write
+ * access of the feature respectively.  Probing a feature will return success
+ * if the feature is supported and all of the optionally indicated GET/SET
+ * methods are supported.  The format of the data portion of the structure is
+ * specific to the given feature.  The data portion is not required for
+ * probing.  GET and SET are mutually exclusive, except for use with PROBE.
+ *
+ * Return 0 on success, -errno on failure.
+ */
+struct vfio_device_feature {
+	__u32	argsz;
+	__u32	flags;
+#define VFIO_DEVICE_FEATURE_MASK	(0xffff) /* 16-bit feature index */
+#define VFIO_DEVICE_FEATURE_GET		(1 << 16) /* Get feature into data[] */
+#define VFIO_DEVICE_FEATURE_SET		(1 << 17) /* Set feature from data[] */
+#define VFIO_DEVICE_FEATURE_PROBE	(1 << 18) /* Probe feature support */
+	__u8	data[];
+};
+
+#define VFIO_DEVICE_FEATURE		_IO(VFIO_TYPE, VFIO_BASE + 17)
+
+/*
+ * Provide support for setting a PCI VF Token, which is used as a shared
+ * secret between PF and VF drivers.  This feature may only be set on a
+ * PCI SR-IOV PF when SR-IOV is enabled on the PF and there are no existing
+ * open VFs.  Data provided when setting this feature is a 16-byte array
+ * (__u8 b[16]), representing a UUID.
+ */
+#define VFIO_DEVICE_FEATURE_PCI_VF_TOKEN	(0)
+
 /* -------- API for Type1 VFIO IOMMU -------- */
 
 /**