scsi: add support for unit attention conditions

Unit attention conditions override any sense data the device already
has.  Their signaling and clearing is handled entirely by the SCSIBus
code, and they are completely transparent to the SCSIDevices.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 91 insertions, 2 deletions

diff --git a/hw/scsi-bus.c b/hw/scsi-bus.c
index bec8d8282b..564b840eb7 100644
--- a/hw/scsi-bus.c
+++ b/hw/scsi-bus.c
@@ -149,6 +149,24 @@ struct SCSIReqOps reqops_invalid_opcode = {
     .send_command = scsi_invalid_command
 };
 
+/* SCSIReqOps implementation for unit attention conditions.  */
+
+static int32_t scsi_unit_attention(SCSIRequest *req, uint8_t *buf)
+{
+    if (req->dev && req->dev->unit_attention.key == UNIT_ATTENTION) {
+        scsi_req_build_sense(req, req->dev->unit_attention);
+    } else if (req->bus->unit_attention.key == UNIT_ATTENTION) {
+        scsi_req_build_sense(req, req->bus->unit_attention);
+    }
+    scsi_req_complete(req, CHECK_CONDITION);
+    return 0;
+}
+
+struct SCSIReqOps reqops_unit_attention = {
+    .size         = sizeof(SCSIRequest),
+    .send_command = scsi_unit_attention
+};
+
 /* SCSIReqOps implementation for REPORT LUNS and for commands sent to
    an invalid LUN.  */
 
@@ -344,6 +362,7 @@ SCSIRequest *scsi_req_alloc(SCSIReqOps *reqops, SCSIDevice *d, uint32_t tag,
 SCSIRequest *scsi_req_new(SCSIDevice *d, uint32_t tag, uint32_t lun,
                           uint8_t *buf, void *hba_private)
 {
+    SCSIBus *bus = DO_UPCAST(SCSIBus, qbus, d->qdev.parent_bus);
     SCSIRequest *req;
     SCSICommand cmd;
 
@@ -358,7 +377,15 @@ SCSIRequest *scsi_req_new(SCSIDevice *d, uint32_t tag, uint32_t lun,
                                       cmd.lba);
         }
 
-        if (lun != d->lun ||
+        if ((d->unit_attention.key == UNIT_ATTENTION ||
+             bus->unit_attention.key == UNIT_ATTENTION) &&
+            (buf[0] != INQUIRY &&
+             buf[0] != REPORT_LUNS &&
+             buf[0] != GET_CONFIGURATION &&
+             buf[0] != GET_EVENT_STATUS_NOTIFICATION)) {
+            req = scsi_req_alloc(&reqops_unit_attention, d, tag, lun,
+                                 hba_private);
+        } else if (lun != d->lun ||
             buf[0] == REPORT_LUNS ||
             buf[0] == REQUEST_SENSE) {
             req = scsi_req_alloc(&reqops_target_command, d, tag, lun,
@@ -377,13 +404,68 @@ uint8_t *scsi_req_get_buf(SCSIRequest *req)
     return req->ops->get_buf(req);
 }
 
+static void scsi_clear_unit_attention(SCSIRequest *req)
+{
+    SCSISense *ua;
+    if (req->dev->unit_attention.key != UNIT_ATTENTION &&
+        req->bus->unit_attention.key != UNIT_ATTENTION) {
+        return;
+    }
+
+    /*
+     * If an INQUIRY command enters the enabled command state,
+     * the device server shall [not] clear any unit attention condition;
+     * See also MMC-6, paragraphs 6.5 and 6.6.2.
+     */
+    if (req->cmd.buf[0] == INQUIRY ||
+        req->cmd.buf[0] == GET_CONFIGURATION ||
+        req->cmd.buf[0] == GET_EVENT_STATUS_NOTIFICATION) {
+        return;
+    }
+
+    if (req->dev->unit_attention.key == UNIT_ATTENTION) {
+        ua = &req->dev->unit_attention;
+    } else {
+        ua = &req->bus->unit_attention;
+    }
+
+    /*
+     * If a REPORT LUNS command enters the enabled command state, [...]
+     * the device server shall clear any pending unit attention condition
+     * with an additional sense code of REPORTED LUNS DATA HAS CHANGED.
+     */
+    if (req->cmd.buf[0] == REPORT_LUNS &&
+        !(ua->asc == SENSE_CODE(REPORTED_LUNS_CHANGED).asc &&
+          ua->ascq == SENSE_CODE(REPORTED_LUNS_CHANGED).ascq)) {
+        return;
+    }
+
+    *ua = SENSE_CODE(NO_SENSE);
+}
+
 int scsi_req_get_sense(SCSIRequest *req, uint8_t *buf, int len)
 {
+    int ret;
+
     assert(len >= 14);
     if (!req->sense_len) {
         return 0;
     }
-    return scsi_build_sense(req->sense, req->sense_len, buf, len, true);
+
+    ret = scsi_build_sense(req->sense, req->sense_len, buf, len, true);
+
+    /*
+     * FIXME: clearing unit attention conditions upon autosense should be done
+     * only if the UA_INTLCK_CTRL field in the Control mode page is set to 00b
+     * (SAM-5, 5.14).
+     *
+     * 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.
+     */
+    scsi_clear_unit_attention(req);
+    return ret;
 }
 
 int scsi_device_get_sense(SCSIDevice *dev, uint8_t *buf, int len, bool fixed)
@@ -983,6 +1065,13 @@ void scsi_req_complete(SCSIRequest *req, int status)
     }
     req->dev->sense_len = req->sense_len;
 
+    /*
+     * Unit attention state is now stored in the device's sense buffer
+     * if the HBA didn't do autosense.  Clear the pending unit attention
+     * flags.
+     */
+    scsi_clear_unit_attention(req);
+
     scsi_req_ref(req);
     scsi_req_dequeue(req);
     req->bus->ops->complete(req, req->status);