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>

hw/scsi-bus.c

diff --git a/hw/scsi-bus.c b/hw/scsi-bus.c
index bec8d82..564b840 100644
--- a/hw/scsi-bus.c
+++ b/hw/scsi-bus.c
@@ -149,6 +149,24 @@
     .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_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 @@
                                       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 @@
     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 @@
     }
     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);

hw/scsi-defs.h

diff --git a/hw/scsi-defs.h b/hw/scsi-defs.h
index 977c38b..ea288fa 100644
--- a/hw/scsi-defs.h
+++ b/hw/scsi-defs.h
@@ -78,6 +78,7 @@
 #define READ_TOC              0x43
 #define REPORT_DENSITY_SUPPORT 0x44
 #define GET_CONFIGURATION     0x46
+#define GET_EVENT_STATUS_NOTIFICATION 0x4a
 #define LOG_SELECT            0x4c
 #define LOG_SENSE             0x4d
 #define MODE_SELECT_10        0x55

hw/scsi.h

diff --git a/hw/scsi.h b/hw/scsi.h
index 4d5b596..09c3606 100644
--- a/hw/scsi.h
+++ b/hw/scsi.h
@@ -62,6 +62,7 @@
     uint32_t id;
     BlockConf conf;
     SCSIDeviceInfo *info;
+    SCSISense unit_attention;
     uint8_t sense[SCSI_SENSE_BUF_SIZE];
     uint32_t sense_len;
     QTAILQ_HEAD(, SCSIRequest) requests;
@@ -105,6 +106,7 @@
     BusState qbus;
     int busnr;
 
+    SCSISense unit_attention;
     int tcq, ndev;
     const SCSIBusOps *ops;