[PATCH v3] virtio-scsi: Send "REPORTED LUNS CHANGED" sense data upon disk hotplug events.

[Venu Busireddy]

Section 5.6.6.3 of VirtIO specification states, "Events will also
be reported via sense codes..." However, no sense data is sent when
VIRTIO_SCSI_EVT_RESET_RESCAN or VIRTIO_SCSI_EVT_RESET_REMOVED events
are reported (when disk hotplug/hotunplug events occur). SCSI layer
on Solaris depends on this sense data, and hence does not handle disk
hotplug/hotunplug events.

When disk inventory changes, return a CHECK_CONDITION status with sense
data of 0x06/0x3F/0x0E (sense code REPORTED_LUNS_CHANGED), as per the
specifications in Section 5.14 (h) of SAM-4.

Signed-off-by: Venu Busireddy <venu.busireddy@oracle.com>

v2 -> v3:
    - Implement the suggestion from Paolo Bonzini <pbonzini@redhat.com>.

v1 -> v2:
    - Send the sense data for VIRTIO_SCSI_EVT_RESET_REMOVED event too.
---
 hw/scsi/scsi-bus.c              |  1 +
 hw/scsi/virtio-scsi.c           | 16 ++++++++++++++++
 include/hw/scsi/scsi.h          |  6 ++++++
 include/hw/virtio/virtio-scsi.h |  1 +
 4 files changed, 24 insertions(+)

diff --git a/hw/scsi/scsi-bus.c b/hw/scsi/scsi-bus.c
index 4403717c4aaf..b7cb249f2eab 100644
--- a/hw/scsi/scsi-bus.c
+++ b/hw/scsi/scsi-bus.c
@@ -730,6 +730,7 @@ SCSIRequest *scsi_req_new(SCSIDevice *d, uint32_t tag, 
uint32_t lun,
           */
          !(buf[0] == REQUEST_SENSE && d->sense_is_ua))) {
         ops = &reqops_unit_attention;
+        d->clear_reported_luns_changed = true;
     } else if (lun != d->lun ||
                buf[0] == REPORT_LUNS ||
                (buf[0] == REQUEST_SENSE && d->sense_len)) {
diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index 41f2a5630173..b7f66d366fcb 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -695,9 +695,23 @@ static int virtio_scsi_handle_cmd_req_prepare(VirtIOSCSI 
*s, VirtIOSCSIReq *req)
         return -ENOENT;
     }
     virtio_scsi_ctx_check(s, d);
+
+    if (s->reported_luns_changed) {
+        scsi_device_set_ua(d, SENSE_CODE(REPORTED_LUNS_CHANGED));
+    }
+
+    /*
+     * set d->clear_reported_luns_changed.
+     * scsi_req_new() will clear it if the required conditions are met.
+     */
+    d->clear_reported_luns_changed = false;
     req->sreq = scsi_req_new(d, req->req.cmd.tag,
                              virtio_scsi_get_lun(req->req.cmd.lun),
                              req->req.cmd.cdb, vs->cdb_size, req);
+    if (d->clear_reported_luns_changed) {
+        s->reported_luns_changed = false;
+        d->clear_reported_luns_changed = false;
+    }
 
     if (req->sreq->cmd.mode != SCSI_XFER_NONE
         && (req->sreq->cmd.mode != req->mode ||
@@ -956,6 +970,7 @@ static void virtio_scsi_hotplug(HotplugHandler 
*hotplug_dev, DeviceState *dev,
         virtio_scsi_push_event(s, sd,
                                VIRTIO_SCSI_T_TRANSPORT_RESET,
                                VIRTIO_SCSI_EVT_RESET_RESCAN);
+        s->reported_luns_changed = true;
         virtio_scsi_release(s);
     }
 }
@@ -973,6 +988,7 @@ static void virtio_scsi_hotunplug(HotplugHandler 
*hotplug_dev, DeviceState *dev,
         virtio_scsi_push_event(s, sd,
                                VIRTIO_SCSI_T_TRANSPORT_RESET,
                                VIRTIO_SCSI_EVT_RESET_REMOVED);
+        s->reported_luns_changed = true;
         virtio_scsi_release(s);
     }
 
diff --git a/include/hw/scsi/scsi.h b/include/hw/scsi/scsi.h
index 001103488c23..ea81c6f89e74 100644
--- a/include/hw/scsi/scsi.h
+++ b/include/hw/scsi/scsi.h
@@ -89,6 +89,12 @@ struct SCSIDevice
     uint32_t io_timeout;
     bool needs_vpd_bl_emulation;
     bool hba_supports_iothread;
+    /*
+     * clear_reported_luns_changed is used, if the required
+     * conditions are met, to inform the virtio-scsi layer that
+     * any pending REPORTED_LUNS_CHANGED condition can be cleared.
+     */
+    bool clear_reported_luns_changed;
 };
 
 extern const VMStateDescription vmstate_scsi_device;
diff --git a/include/hw/virtio/virtio-scsi.h b/include/hw/virtio/virtio-scsi.h
index a36aad9c8695..efbcf9ba069a 100644
--- a/include/hw/virtio/virtio-scsi.h
+++ b/include/hw/virtio/virtio-scsi.h
@@ -81,6 +81,7 @@ struct VirtIOSCSI {
     SCSIBus bus;
     int resetting;
     bool events_dropped;
+    bool reported_luns_changed;
 
     /* Fields for dataplane below */
     AioContext *ctx; /* one iothread per virtio-scsi-pci for now */