From: Nicolin Chen <redacted>
Sent: Saturday, January 25, 2025 8:31 AM
+
+/*
+ * An iommufd_veventq object represents an interface to deliver vIOMMU
events to
+ * the user space. It is created/destroyed by the user space and associated
with
+ * vIOMMU object(s) during the allocations.

s/object(s)/object/, given the eventq cannot be shared between vIOMMUs.

+static inline void iommufd_vevent_handler(struct iommufd_veventq
*veventq,
+					  struct iommufd_vevent *vevent)
+{
+	struct iommufd_eventq *eventq = &veventq->common;
+
+	/*
+	 * Remove the overflow node and add the new node at the same
time. Note
+	 * it is possible that vevent == &veventq->overflow for sequence
update
+	 */
+	spin_lock(&eventq->lock);
+	if (veventq->overflow.on_list) {
+		list_del(&veventq->overflow.node);
+		veventq->overflow.on_list = false;
+	}

We can save one field 'on_list' in every entry by:

	if (list_is_last(&veventq->overflow.node, &eventq->deliver))
		list_del(&veventq->overflow.node);

+
+/**
+ * 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
+ * @__reserved: Must be 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 indicates that an overflow occurred to the vEVENTQ and that delta - 1
+ * number of vEVENTs lost due to the overflow (e.g. two lost vEVENTs):
+ *  ---------------------------------------------------------------------------
+ * || ... | header3 {sequence=3} | data3 | header6 {sequence=6} | data6 | ...
||
+ *  ---------------------------------------------------------------------------
+ * If an overflow occurred to the tail of the vEVENTQ and there is no
following
+ * vEVENT providing the next sequence index, a special overflow header
would be
+ * added to the tail of the vEVENTQ, where there would be no more type-
specific
+ * data following the vEVENTQ:
+ *  ---------------------------------------------------------------------------
+ * ||...| header3 {sequence=3} | data4 | header4 {flags=OVERFLOW,
sequence=4} ||
+ *  ---------------------------------------------------------------------------
+ */
+struct iommufd_vevent_header {
+	__aligned_u64 flags;
+	__u32 sequence;
+	__u32 __reserved;
+};

Is there a reason that flags must be u64? At a glance all flags fields
(except the one in iommu_hwpt_vtd_s1) in iommufd uAPIs are u32
which can cut the size of the header by half...

+void iommufd_veventq_abort(struct iommufd_object *obj)
+{
+	struct iommufd_eventq *eventq =
+		container_of(obj, struct iommufd_eventq, obj);
+	struct iommufd_veventq *veventq = eventq_to_veventq(eventq);
+	struct iommufd_viommu *viommu = veventq->viommu;
+	struct iommufd_vevent *cur, *next;
+
+	lockdep_assert_held_write(&viommu->veventqs_rwsem);
+
+	list_for_each_entry_safe(cur, next, &eventq->deliver, node) {
+		list_del(&cur->node);
+		kfree(cur);

kfree() doesn't apply to the overflow node.

otherwise it looks good to me:

Reviewed-by: Kevin Tian <kevin.tian@intel.com>