scsi: support FUA on reads

To force unit access on reads, flush the cache *before* doing the read.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/scsi-disk.c

@@ -278,12 +278,48 @@ done:
     }
 }
 
+/* Actually issue a read to the block device.  */
+static void scsi_do_read(void *opaque, int ret)
+{
+    SCSIDiskReq *r = opaque;
+    SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
+    uint32_t n;
+
+    if (r->req.aiocb != NULL) {
+        r->req.aiocb = NULL;
+        bdrv_acct_done(s->qdev.conf.bs, &r->acct);
+    }
+
+    if (ret < 0) {
+        if (scsi_handle_rw_error(r, -ret)) {
+            goto done;
+        }
+    }
+
+    if (r->req.sg) {
+        dma_acct_start(s->qdev.conf.bs, &r->acct, r->req.sg, BDRV_ACCT_READ);
+        r->req.resid -= r->req.sg->size;
+        r->req.aiocb = dma_bdrv_read(s->qdev.conf.bs, r->req.sg, r->sector,
+                                     scsi_dma_complete, r);
+    } else {
+        n = scsi_init_iovec(r, SCSI_DMA_BUF_SIZE);
+        bdrv_acct_start(s->qdev.conf.bs, &r->acct, n * BDRV_SECTOR_SIZE, BDRV_ACCT_READ);
+        r->req.aiocb = bdrv_aio_readv(s->qdev.conf.bs, r->sector, &r->qiov, n,
+                                      scsi_read_complete, r);
+    }
+
+done:
+    if (!r->req.io_canceled) {
+        scsi_req_unref(&r->req);
+    }
+}
+
 /* Read more data from scsi device into buffer.  */
 static void scsi_read_data(SCSIRequest *req)
 {
     SCSIDiskReq *r = DO_UPCAST(SCSIDiskReq, req, req);
     SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
-    uint32_t n;
+    bool first;
 
     if (r->sector_count == (uint32_t)-1) {
         DPRINTF("Read buf_len=%zd\n", r->iov.iov_len);
@@ -315,17 +351,13 @@ static void scsi_read_data(SCSIRequest *req)
         return;
     }
 
+    first = !r->started;
     r->started = true;
-    if (r->req.sg) {
-        dma_acct_start(s->qdev.conf.bs, &r->acct, r->req.sg, BDRV_ACCT_READ);
-        r->req.resid -= r->req.sg->size;
-        r->req.aiocb = dma_bdrv_read(s->qdev.conf.bs, r->req.sg, r->sector,
-                                     scsi_dma_complete, r);
+    if (first && scsi_is_cmd_fua(&r->req.cmd)) {
+        bdrv_acct_start(s->qdev.conf.bs, &r->acct, 0, BDRV_ACCT_FLUSH);
+        r->req.aiocb = bdrv_aio_flush(s->qdev.conf.bs, scsi_do_read, r);
     } else {
-        n = scsi_init_iovec(r, SCSI_DMA_BUF_SIZE);
-        bdrv_acct_start(s->qdev.conf.bs, &r->acct, n * BDRV_SECTOR_SIZE, BDRV_ACCT_READ);
-        r->req.aiocb = bdrv_aio_readv(s->qdev.conf.bs, r->sector, &r->qiov, n,
-                                      scsi_read_complete, r);
+        scsi_do_read(r, 0);
     }
 }