scsi: notify the device when unit attention is reported

Reporting media change events via unit attention sense codes requires
a small state machine: first report "NO MEDIUM", then report "MEDIUM MAY
HAVE CHANGED".  Unfortunately there is no good hooking point for the
device to notice that its pending unit attention condition has been
reported.  This patch reworks the generic machinery to add one.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

hw/scsi-bus.c

diff --git a/hw/scsi-bus.c b/hw/scsi-bus.c
index fc2f823..c190509 100644
--- a/hw/scsi-bus.c
+++ b/hw/scsi-bus.c
@@ -295,6 +295,13 @@
         r->len = scsi_device_get_sense(r->req.dev, r->buf,
                                        MIN(req->cmd.xfer, sizeof r->buf),
                                        (req->cmd.buf[1] & 1) == 0);
+        if (r->req.dev->sense_is_ua) {
+            if (r->req.dev->info->unit_attention_reported) {
+                r->req.dev->info->unit_attention_reported(req->dev);
+            }
+            r->req.dev->sense_len = 0;
+            r->req.dev->sense_is_ua = false;
+        }
         break;
     default:
         scsi_req_build_sense(req, SENSE_CODE(LUN_NOT_SUPPORTED));
@@ -383,7 +390,13 @@
             (buf[0] != INQUIRY &&
              buf[0] != REPORT_LUNS &&
              buf[0] != GET_CONFIGURATION &&
-             buf[0] != GET_EVENT_STATUS_NOTIFICATION)) {
+             buf[0] != GET_EVENT_STATUS_NOTIFICATION &&
+
+             /*
+              * If we already have a pending unit attention condition,
+              * report this one before triggering another one.
+              */
+             !(buf[0] == REQUEST_SENSE && d->sense_is_ua))) {
             req = scsi_req_alloc(&reqops_unit_attention, d, tag, lun,
                                  hba_private);
         } else if (lun != d->lun ||
@@ -479,10 +492,15 @@
      *
      * We assume UA_INTLCK_CTRL to be 00b for HBAs that support autosense, and
      * 10b for HBAs that do not support it (do not call scsi_req_get_sense).
-     * In the latter case, scsi_req_complete clears unit attention conditions
-     * after moving them to the device's sense buffer.
+     * Here we handle unit attention clearing for UA_INTLCK_CTRL == 00b.
      */
-    scsi_clear_unit_attention(req);
+    if (req->dev->sense_is_ua) {
+        if (req->dev->info->unit_attention_reported) {
+            req->dev->info->unit_attention_reported(req->dev);
+        }
+        req->dev->sense_len = 0;
+        req->dev->sense_is_ua = false;
+    }
     return ret;
 }
 
@@ -1082,8 +1100,12 @@
 
     if (req->sense_len) {
         memcpy(req->dev->sense, req->sense, req->sense_len);
+        req->dev->sense_len = req->sense_len;
+        req->dev->sense_is_ua = (req->ops == &reqops_unit_attention);
+    } else {
+        req->dev->sense_len = 0;
+        req->dev->sense_is_ua = false;
     }
-    req->dev->sense_len = req->sense_len;
 
     /*
      * Unit attention state is now stored in the device's sense buffer

hw/scsi.h

diff --git a/hw/scsi.h b/hw/scsi.h
index e8dcabf..6d40b8e 100644
--- a/hw/scsi.h
+++ b/hw/scsi.h
@@ -62,6 +62,7 @@
     BlockConf conf;
     SCSIDeviceInfo *info;
     SCSISense unit_attention;
+    bool sense_is_ua;
     uint8_t sense[SCSI_SENSE_BUF_SIZE];
     uint32_t sense_len;
     QTAILQ_HEAD(, SCSIRequest) requests;
@@ -92,6 +93,7 @@
     void (*destroy)(SCSIDevice *s);
     SCSIRequest *(*alloc_req)(SCSIDevice *s, uint32_t tag, uint32_t lun,
                               void *hba_private);
+    void (*unit_attention_reported)(SCSIDevice *s);
     SCSIReqOps reqops;
 };