scsi: prepare migration code for usb-storage support

usb-storage can't handle requests in one go as the data transfer can be
splitted into lots of usb packets.  Because of that there can be
normal in-flight requests at savevm time and we need to handle that.
With other scsi hba's this happens only in case i/o is stopped due to
errors and there are pending requests which need to be restarted
(req->retry = true).

So, first we need to save req->retry and then handle the req->retry =
false case.  Write requests are handled fine already.  For read requests
we have to save the buffer as we will not restart the request (and thus
not refill the buffer) on the target host.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

2 files changed, 18 insertions, 6 deletions

diff --git a/hw/scsi-bus.c b/hw/scsi-bus.c
index f10f3ec25c..4a798210ce 100644
--- a/hw/scsi-bus.c
+++ b/hw/scsi-bus.c
@@ -1507,10 +1507,9 @@ static void put_scsi_requests(QEMUFile *f, void *pv, size_t size)
     QTAILQ_FOREACH(req, &s->requests, next) {
         assert(!req->io_canceled);
         assert(req->status == -1);
-        assert(req->retry);
         assert(req->enqueued);
 
-        qemu_put_sbyte(f, 1);
+        qemu_put_sbyte(f, req->retry ? 1 : 2);
         qemu_put_buffer(f, req->cmd.buf, sizeof(req->cmd.buf));
         qemu_put_be32s(f, &req->tag);
         qemu_put_be32s(f, &req->lun);
@@ -1528,8 +1527,9 @@ static int get_scsi_requests(QEMUFile *f, void *pv, size_t size)
 {
     SCSIDevice *s = pv;
     SCSIBus *bus = DO_UPCAST(SCSIBus, qbus, s->qdev.parent_bus);
+    int8_t sbyte;
 
-    while (qemu_get_sbyte(f)) {
+    while ((sbyte = qemu_get_sbyte(f)) > 0) {
         uint8_t buf[SCSI_CMD_BUF_SIZE];
         uint32_t tag;
         uint32_t lun;
@@ -1539,6 +1539,7 @@ static int get_scsi_requests(QEMUFile *f, void *pv, size_t size)
         qemu_get_be32s(f, &tag);
         qemu_get_be32s(f, &lun);
         req = scsi_req_new(s, tag, lun, buf, NULL);
+        req->retry = (sbyte == 1);
         if (bus->info->load_request) {
             req->hba_private = bus->info->load_request(f, req);
         }
@@ -1547,7 +1548,6 @@ static int get_scsi_requests(QEMUFile *f, void *pv, size_t size)
         }
 
         /* Just restart it later.  */
-        req->retry = true;
         scsi_req_enqueue_internal(req);
 
         /* At this point, the request will be kept alive by the reference
diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
index 045c764d9b..1691491c03 100644
--- a/hw/scsi-disk.c
+++ b/hw/scsi-disk.c
@@ -132,8 +132,14 @@ static void scsi_disk_save_request(QEMUFile *f, SCSIRequest *req)
     qemu_put_be64s(f, &r->sector);
     qemu_put_be32s(f, &r->sector_count);
     qemu_put_be32s(f, &r->buflen);
-    if (r->buflen && r->req.cmd.mode == SCSI_XFER_TO_DEV) {
-        qemu_put_buffer(f, r->iov.iov_base, r->iov.iov_len);
+    if (r->buflen) {
+        if (r->req.cmd.mode == SCSI_XFER_TO_DEV) {
+            qemu_put_buffer(f, r->iov.iov_base, r->iov.iov_len);
+        } else if (!req->retry) {
+            uint32_t len = r->iov.iov_len;
+            qemu_put_be32s(f, &len);
+            qemu_put_buffer(f, r->iov.iov_base, r->iov.iov_len);
+        }
     }
 }
 
@@ -148,6 +154,12 @@ static void scsi_disk_load_request(QEMUFile *f, SCSIRequest *req)
         scsi_init_iovec(r, r->buflen);
         if (r->req.cmd.mode == SCSI_XFER_TO_DEV) {
             qemu_get_buffer(f, r->iov.iov_base, r->iov.iov_len);
+        } else if (!r->req.retry) {
+            uint32_t len;
+            qemu_get_be32s(f, &len);
+            r->iov.iov_len = len;
+            assert(r->iov.iov_len <= r->buflen);
+            qemu_get_buffer(f, r->iov.iov_base, r->iov.iov_len);
         }
     }