Move the vEVENTQ read and validation logic into a common helper.

The helper performs the read(), checks for overflow and short reads,
validates the sequence number, and updates the sequence state.

This helper can be reused in the subsequent patch for Tegra241 CMDQV
vEVENTQ support.

Error handling is slightly adjusted: instead of reporting errors
directly in the read handler, the helper now returns errors via
Error **. Sequence gaps are reported as warnings.

Signed-off-by: Shameer Kolothum <skolothumtho@nvidia.com>
---
 hw/arm/smmuv3-accel.h       |  2 ++
 hw/arm/smmuv3-accel-stubs.c |  6 ++++
 hw/arm/smmuv3-accel.c       | 67 ++++++++++++++++++++++---------------
 3 files changed, 48 insertions(+), 27 deletions(-)

diff --git a/hw/arm/smmuv3-accel.h b/hw/arm/smmuv3-accel.h
index 4bff90e2c1..c349981e79 100644
--- a/hw/arm/smmuv3-accel.h
+++ b/hw/arm/smmuv3-accel.h
@@ -70,6 +70,8 @@ bool smmuv3_accel_issue_inv_cmd(SMMUv3State *s, void *cmd, SMMUDevice *sdev,
                                 Error **errp);
 void smmuv3_accel_idr_override(SMMUv3State *s);
 bool smmuv3_accel_alloc_veventq(SMMUv3State *s, Error **errp);
+bool smmuv3_accel_event_read_validate(IOMMUFDVeventq *veventq, uint32_t type,
+                                      void *buf, size_t size, Error **errp);
 void smmuv3_accel_reset(SMMUv3State *s);
 
 #endif /* HW_ARM_SMMUV3_ACCEL_H */
diff --git a/hw/arm/smmuv3-accel-stubs.c b/hw/arm/smmuv3-accel-stubs.c
index 870fc2a71c..1d5d3bb10c 100644
--- a/hw/arm/smmuv3-accel-stubs.c
+++ b/hw/arm/smmuv3-accel-stubs.c
@@ -42,6 +42,12 @@ bool smmuv3_accel_alloc_veventq(SMMUv3State *s, Error **errp)
     return true;
 }
 
+bool smmuv3_accel_event_read_validate(IOMMUFDVeventq *veventq, uint32_t type,
+                                      void *buf, size_t size, Error **errp)
+{
+    return true;
+}
+
 void smmuv3_accel_idr_override(SMMUv3State *s)
 {
 }
diff --git a/hw/arm/smmuv3-accel.c b/hw/arm/smmuv3-accel.c
index f6602f51aa..5f296ea763 100644
--- a/hw/arm/smmuv3-accel.c
+++ b/hw/arm/smmuv3-accel.c
@@ -391,47 +391,60 @@ bool smmuv3_accel_issue_inv_cmd(SMMUv3State *bs, void *cmd, SMMUDevice *sdev,
                    sizeof(Cmd), &entry_num, cmd, errp);
 }
 
-static void smmuv3_accel_event_read(void *opaque)
+bool smmuv3_accel_event_read_validate(IOMMUFDVeventq *veventq, uint32_t type,
+                                      void *buf, size_t size, Error **errp)
 {
-    SMMUv3State *s = opaque;
-    IOMMUFDVeventq *veventq = s->s_accel->veventq;
-    struct {
-        struct iommufd_vevent_header hdr;
-        struct iommu_vevent_arm_smmuv3 vevent;
-    } buf;
-    enum iommu_veventq_type type = IOMMU_VEVENTQ_TYPE_ARM_SMMUV3;
-    uint32_t id = veventq->veventq_id;
     uint32_t last_seq = veventq->last_event_seq;
+    uint32_t id = veventq->veventq_id;
+    struct iommufd_vevent_header *hdr;
     ssize_t bytes;
 
-    bytes = read(veventq->veventq_fd, &buf, sizeof(buf));
+    bytes = read(veventq->veventq_fd, buf, size);
     if (bytes <= 0) {
         if (errno == EAGAIN || errno == EINTR) {
-            return;
+            return true;
         }
-        error_report_once("vEVENTQ(type %u id %u): read failed (%m)", type, id);
-        return;
+        error_setg(errp, "vEVENTQ(type %u id %u): read failed (%m)", type, id);
+        return false;
     }
-
-    if (bytes == sizeof(buf.hdr) &&
-        (buf.hdr.flags & IOMMU_VEVENTQ_FLAG_LOST_EVENTS)) {
-        error_report_once("vEVENTQ(type %u id %u): overflowed", type, id);
+    hdr = (struct iommufd_vevent_header *)buf;
+    if (bytes == sizeof(*hdr) &&
+        (hdr->flags & IOMMU_VEVENTQ_FLAG_LOST_EVENTS)) {
+        error_setg(errp, "vEVENTQ(type %u id %u): overflowed", type, id);
         veventq->event_start = false;
-        return;
+        return false;
     }
-    if (bytes < sizeof(buf)) {
-        error_report_once("vEVENTQ(type %u id %u): short read(%zd/%zd bytes)",
-                          type, id, bytes, sizeof(buf));
-        return;
+    if (bytes < size) {
+        error_setg(errp, "vEVENTQ(type %u id %u): short read(%zd/%zd bytes)",
+                          type, id, bytes, size);
+        return false;
     }
-
     /* Check sequence in hdr for lost events if any */
-    if (veventq->event_start && (buf.hdr.sequence - last_seq != 1)) {
-        error_report_once("vEVENTQ(type %u id %u): lost %u event(s)",
-                          type, id, buf.hdr.sequence - last_seq - 1);
+    if (veventq->event_start && (hdr->sequence - last_seq != 1)) {
+        warn_report("vEVENTQ(type %u id %u): lost %u event(s)",
+                    type, id, hdr->sequence - last_seq - 1);
     }
-    veventq->last_event_seq = buf.hdr.sequence;
+    veventq->last_event_seq = hdr->sequence;
     veventq->event_start = true;
+    return true;
+}
+
+static void smmuv3_accel_event_read(void *opaque)
+{
+    SMMUv3State *s = opaque;
+    IOMMUFDVeventq *veventq = s->s_accel->veventq;
+    struct {
+        struct iommufd_vevent_header hdr;
+        struct iommu_vevent_arm_smmuv3 vevent;
+    } buf;
+    Error *local_err;
+
+    if (!smmuv3_accel_event_read_validate(veventq,
+                                          IOMMU_VEVENTQ_TYPE_ARM_SMMUV3, &buf,
+                                          sizeof(buf), &local_err)) {
+        warn_report_err_once(local_err);
+        return;
+    }
     smmuv3_propagate_event(s, (Evt *)&buf.vevent);
 }
 
-- 
2.43.0