iommufd: Add IOMMUFD_OBJ_VEVENTQ and IOMMUFD_CMD_VEVENTQ_ALLOC

Introduce a new IOMMUFD_OBJ_VEVENTQ object for vIOMMU Event Queue that
provides user space (VMM) another FD to read the vIOMMU Events.

Allow a vIOMMU object to allocate vEVENTQs, with a condition that each
vIOMMU can only have one single vEVENTQ per type.

Add iommufd_veventq_alloc() with iommufd_veventq_ops for the new ioctl.

Link: https://patch.msgid.link/r/21acf0751dd5c93846935ee06f93b9c65eff5e04.1741719725.git.nicolinc@nvidia.com
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

1 files changed, 82 insertions, 0 deletions

diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
index 78747b24bd0f..dbb8787d9c63 100644
--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -55,6 +55,7 @@ enum {
 	IOMMUFD_CMD_VIOMMU_ALLOC = 0x90,
 	IOMMUFD_CMD_VDEVICE_ALLOC = 0x91,
 	IOMMUFD_CMD_IOAS_CHANGE_PROCESS = 0x92,
+	IOMMUFD_CMD_VEVENTQ_ALLOC = 0x93,
 };
 
 /**
@@ -1014,4 +1015,85 @@ struct iommu_ioas_change_process {
 #define IOMMU_IOAS_CHANGE_PROCESS \
 	_IO(IOMMUFD_TYPE, IOMMUFD_CMD_IOAS_CHANGE_PROCESS)
 
+/**
+ * enum iommu_veventq_flag - flag for struct iommufd_vevent_header
+ * @IOMMU_VEVENTQ_FLAG_LOST_EVENTS: vEVENTQ has lost vEVENTs
+ */
+enum iommu_veventq_flag {
+	IOMMU_VEVENTQ_FLAG_LOST_EVENTS = (1U << 0),
+};
+
+/**
+ * struct iommufd_vevent_header - Virtual Event Header for a vEVENTQ Status
+ * @flags: Combination of enum iommu_veventq_flag
+ * @sequence: The sequence index of a vEVENT in the vEVENTQ, with a range of
+ *            [0, INT_MAX] where the following index of INT_MAX is 0
+ *
+ * Each iommufd_vevent_header reports a sequence index of the following vEVENT:
+ *  -------------------------------------------------------------------------
+ * | header0 {sequence=0} | data0 | header1 {sequence=1} | data1 |...| dataN |
+ *  -------------------------------------------------------------------------
+ * And this sequence index is expected to be monotonic to the sequence index of
+ * the previous vEVENT. If two adjacent sequence indexes has a delta larger than
+ * 1, it means that delta - 1 number of vEVENTs has lost, e.g. two lost vEVENTs:
+ *  -------------------------------------------------------------------------
+ * | ... | header3 {sequence=3} | data3 | header6 {sequence=6} | data6 | ... |
+ *  -------------------------------------------------------------------------
+ * If a vEVENT lost at the tail of the vEVENTQ and there is no following vEVENT
+ * providing the next sequence index, an IOMMU_VEVENTQ_FLAG_LOST_EVENTS header
+ * would be added to the tail, and no data would follow this header:
+ *  ---------------------------------------------------------------------------
+ * |..| header3 {sequence=3} | data3 | header4 {flags=LOST_EVENTS, sequence=4} |
+ *  ---------------------------------------------------------------------------
+ */
+struct iommufd_vevent_header {
+	__u32 flags;
+	__u32 sequence;
+};
+
+/**
+ * enum iommu_veventq_type - Virtual Event Queue Type
+ * @IOMMU_VEVENTQ_TYPE_DEFAULT: Reserved for future use
+ */
+enum iommu_veventq_type {
+	IOMMU_VEVENTQ_TYPE_DEFAULT = 0,
+};
+
+/**
+ * struct iommu_veventq_alloc - ioctl(IOMMU_VEVENTQ_ALLOC)
+ * @size: sizeof(struct iommu_veventq_alloc)
+ * @flags: Must be 0
+ * @viommu_id: virtual IOMMU ID to associate the vEVENTQ with
+ * @type: Type of the vEVENTQ. Must be defined in enum iommu_veventq_type
+ * @veventq_depth: Maximum number of events in the vEVENTQ
+ * @out_veventq_id: The ID of the new vEVENTQ
+ * @out_veventq_fd: The fd of the new vEVENTQ. User space must close the
+ *                  successfully returned fd after using it
+ * @__reserved: Must be 0
+ *
+ * Explicitly allocate a virtual event queue interface for a vIOMMU. A vIOMMU
+ * can have multiple FDs for different types, but is confined to one per @type.
+ * User space should open the @out_veventq_fd to read vEVENTs out of a vEVENTQ,
+ * if there are vEVENTs available. A vEVENTQ will lose events due to overflow,
+ * if the number of the vEVENTs hits @veventq_depth.
+ *
+ * Each vEVENT in a vEVENTQ encloses a struct iommufd_vevent_header followed by
+ * a type-specific data structure, in a normal case:
+ *  -------------------------------------------------------------
+ * || header0 | data0 | header1 | data1 | ... | headerN | dataN ||
+ *  -------------------------------------------------------------
+ * unless a tailing IOMMU_VEVENTQ_FLAG_LOST_EVENTS header is logged (refer to
+ * struct iommufd_vevent_header).
+ */
+struct iommu_veventq_alloc {
+	__u32 size;
+	__u32 flags;
+	__u32 viommu_id;
+	__u32 type;
+	__u32 veventq_depth;
+	__u32 out_veventq_id;
+	__u32 out_veventq_fd;
+	__u32 __reserved;
+};
+#define IOMMU_VEVENTQ_ALLOC _IO(IOMMUFD_TYPE, IOMMUFD_CMD_VEVENTQ_ALLOC)
 #endif