[Qemu-devel] [PATCH 06/11] scsi: add scatter/gather functionality

[Paolo Bonzini <pbonzini@redhat.com>]

Scatter/gather functionality uses the newly added DMA helpers.  The
device can choose between doing DMA itself, or calling scsi_req_data
as usual.  In the latter case, scsi_req_data will use the buffer-based
DMA helpers to copy piecewise to/from the destination area(s).

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/esp.c         |    2 +-
 hw/lsi53c895a.c  |    2 +-
 hw/scsi-bus.c    |   28 ++++++++++++++++++++++++----
 hw/scsi.h        |    4 +++-
 hw/spapr_vscsi.c |    2 +-
 hw/usb-msd.c     |    2 +-
 6 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/hw/esp.c b/hw/esp.c
index 8516db5..e72e8ba 100644
--- a/hw/esp.c
+++ b/hw/esp.c
@@ -239,7 +239,7 @@ static void do_busid_cmd(ESPState *s, uint8_t *buf, uint8_t busid)
     lun = busid & 7;
     current_lun = scsi_device_find(&s->bus, 0, s->current_dev->id, lun);
     s->current_req = scsi_req_new(current_lun, 0, lun, buf, NULL);
-    datalen = scsi_req_enqueue(s->current_req);
+    datalen = scsi_req_enqueue(s->current_req, NULL);
     s->ti_size = datalen;
     if (datalen != 0) {
         s->rregs[ESP_RSTAT] = STAT_TC;
diff --git a/hw/lsi53c895a.c b/hw/lsi53c895a.c
index c53760b..55533af 100644
--- a/hw/lsi53c895a.c
+++ b/hw/lsi53c895a.c
@@ -778,7 +778,7 @@ static void lsi_do_command(LSIState *s)
     s->current->req = scsi_req_new(dev, s->current->tag, s->current_lun, buf,
                                    s->current);
 
-    n = scsi_req_enqueue(s->current->req);
+    n = scsi_req_enqueue(s->current->req, NULL);
     if (n) {
         if (n > 0) {
             lsi_set_phase(s, PHASE_DI);
diff --git a/hw/scsi-bus.c b/hw/scsi-bus.c
index aa811f4..b42c3b1 100644
--- a/hw/scsi-bus.c
+++ b/hw/scsi-bus.c
@@ -5,6 +5,7 @@
 #include "qdev.h"
 #include "blockdev.h"
 #include "trace.h"
+#include "dma.h"
 
 static char *scsibus_get_fw_dev_path(DeviceState *dev);
 static int scsi_req_parse(SCSICommand *cmd, SCSIDevice *dev, uint8_t *buf);
@@ -51,7 +52,7 @@ static void scsi_dma_restart_bh(void *opaque)
                 break;
             case SCSI_XFER_NONE:
                 scsi_req_dequeue(req);
-                scsi_req_enqueue(req);
+                scsi_req_enqueue(req, NULL);
                 break;
             }
         }
@@ -626,7 +627,7 @@ void scsi_req_build_sense(SCSIRequest *req, SCSISense sense)
     req->sense_len = 18;
 }
 
-int32_t scsi_req_enqueue(SCSIRequest *req)
+int32_t scsi_req_enqueue(SCSIRequest *req, QEMUSGList *sg)
 {
     int32_t rc;
 
@@ -634,6 +635,7 @@ int32_t scsi_req_enqueue(SCSIRequest *req)
     scsi_req_ref(req);
     req->enqueued = true;
     QTAILQ_INSERT_TAIL(&req->dev->requests, req, next);
+    req->sg = sg;
 
     scsi_req_ref(req);
     rc = req->ops->send_command(req, req->cmd.buf);
@@ -1256,14 +1258,32 @@ void scsi_req_continue(SCSIRequest *req)
    Once it completes, calling scsi_req_continue will restart I/O.  */
 void scsi_req_data(SCSIRequest *req, int len)
 {
+    uint8_t *buf;
     if (req->io_canceled) {
         trace_scsi_req_data_canceled(req->dev->id, req->lun, req->tag, len);
         return;
     }
     trace_scsi_req_data(req->dev->id, req->lun, req->tag, len);
     assert(req->cmd.mode != SCSI_XFER_NONE);
-    req->resid -= len;
-    req->bus->info->transfer_data(req, len);
+    if (!req->sg) {
+        req->resid -= len;
+        req->bus->info->transfer_data(req, len);
+        return;
+    }
+
+    /* If the device calls scsi_req_data and the HBA specified a
+     * scatter/gather list, the transfer has to happen in a single
+     * step.  */
+    assert(!req->dma_started);
+    req->dma_started = true;
+
+    buf = scsi_req_get_buf(req);
+    if (req->cmd.mode == SCSI_XFER_FROM_DEV) {
+        req->resid = dma_buf_read(buf, len, req->sg);
+    } else {
+        req->resid = dma_buf_write(buf, len, req->sg);
+    }
+    scsi_req_continue(req);
 }
 
 void scsi_req_print(SCSIRequest *req)
diff --git a/hw/scsi.h b/hw/scsi.h
index 27ca087..8d84c8f 100644
--- a/hw/scsi.h
+++ b/hw/scsi.h
@@ -50,6 +50,8 @@ struct SCSIRequest {
     size_t            resid;
     SCSICommand       cmd;
     BlockDriverAIOCB  *aiocb;
+    QEMUSGList        *sg;
+    bool              dma_started;
     uint8_t sense[SCSI_SENSE_BUF_SIZE];
     uint32_t sense_len;
     bool enqueued;
@@ -187,7 +189,7 @@ SCSIRequest *scsi_req_alloc(const SCSIReqOps *reqops, SCSIDevice *d,
                             uint32_t tag, uint32_t lun, void *hba_private);
 SCSIRequest *scsi_req_new(SCSIDevice *d, uint32_t tag, uint32_t lun,
                           uint8_t *buf, void *hba_private);
-int32_t scsi_req_enqueue(SCSIRequest *req);
+int32_t scsi_req_enqueue(SCSIRequest *req, QEMUSGList *qsg);
 void scsi_req_free(SCSIRequest *req);
 SCSIRequest *scsi_req_ref(SCSIRequest *req);
 void scsi_req_unref(SCSIRequest *req);
diff --git a/hw/spapr_vscsi.c b/hw/spapr_vscsi.c
index c28bba9..fe4ca65 100644
--- a/hw/spapr_vscsi.c
+++ b/hw/spapr_vscsi.c
@@ -624,7 +624,7 @@ static int vscsi_queue_cmd(VSCSIState *s, vscsi_req *req)
 
     req->lun = lun;
     req->sreq = scsi_req_new(sdev, req->qtag, lun, srp->cmd.cdb, req);
-    n = scsi_req_enqueue(req->sreq);
+    n = scsi_req_enqueue(req->sreq, NULL);
 
     dprintf("VSCSI: Queued command tag 0x%x CMD 0x%x ID %d LUN %d ret: %d\n",
             req->qtag, srp->cmd.cdb[0], id, lun, n);
diff --git a/hw/usb-msd.c b/hw/usb-msd.c
index 1c7bc82..68a9f53 100644
--- a/hw/usb-msd.c
+++ b/hw/usb-msd.c
@@ -377,7 +377,7 @@ static int usb_msd_handle_data(USBDevice *dev, USBPacket *p)
             s->residue = 0;
             s->scsi_len = 0;
             s->req = scsi_req_new(s->scsi_dev, tag, 0, cbw.cmd, NULL);
-            scsi_req_enqueue(s->req);
+            scsi_req_enqueue(s->req, NULL);
             if (s->req && s->req->cmd.xfer != SCSI_XFER_NONE) {
                 scsi_req_continue(s->req);
             }
-- 
1.7.7.1