[Qemu-devel] [PATCH 3/3] SG support (Asynchronous Send Command)

[Laurent Vivier]

This patch modifies scsi_send_command() to use asynchronous I/O with
SCSI Generic.

This allows to use command with data transfers that are not immediate.
Old behavior can generate softlockup in the guest kernel.

hw/lsi53c895a.c has been modified to manage this new behavior.

---
 hw/lsi53c895a.c   |   25 ++++++++++++++++++-------
 hw/scsi-generic.c |    3 +--
 2 files changed, 19 insertions(+), 9 deletions(-)

Index: qemu/hw/lsi53c895a.c
===================================================================
--- qemu.orig/hw/lsi53c895a.c   2007-11-28 13:12:22.000000000 +0100
+++ qemu/hw/lsi53c895a.c        2007-11-28 13:13:42.000000000 +0100
@@ -187,6 +187,7 @@ typedef struct {
     /* The tag is a combination of the device ID and the SCSI tag.  */
     uint32_t current_tag;
     uint32_t current_dma_len;
+    int command_complete;
     uint8_t *dma_buf;
     lsi_queue *queue;
     int queue_len;
@@ -597,6 +598,7 @@ static void lsi_command_complete(void *o
     if (reason == SCSI_REASON_DONE) {
         DPRINTF("Command complete sense=%d\n", (int)arg);
         s->sense = arg;
+        s->command_complete = 2;
         if (s->waiting && s->dbc != 0) {
             /* Raise phase mismatch for short transfers.  */
             lsi_bad_phase(s, out, PHASE_ST);
@@ -613,6 +615,7 @@ static void lsi_command_complete(void *o
     }
     DPRINTF("Data ready tag=0x%x len=%d\n", tag, arg);
     s->current_dma_len = arg;
+    s->command_complete = 1;
     if (!s->waiting)
         return;
     if (s->waiting == 1 || s->dbc == 0) {
@@ -632,6 +635,7 @@ static void lsi_do_command(LSIState *s)
         s->dbc = 16;
     cpu_physical_memory_read(s->dnad, buf, s->dbc);
     s->sfbr = buf[0];
+    s->command_complete = 0;
     n = s->current_dev->send_command(s->current_dev, s->current_tag, buf,
                                      s->current_lun);
     if (n > 0) {
@@ -641,13 +645,20 @@ static void lsi_do_command(LSIState *s)
         lsi_set_phase(s, PHASE_DO);
         s->current_dev->write_data(s->current_dev, s->current_tag);
     }
-    if (n && s->current_dma_len == 0) {
-        /* Command did not complete immediately so disconnect.  */
-        lsi_add_msg_byte(s, 2); /* SAVE DATA POINTER */
-        lsi_add_msg_byte(s, 4); /* DISCONNECT */
-        lsi_set_phase(s, PHASE_MI);
-        s->msg_action = 1;
-        lsi_queue_command(s);
+
+    if (!s->command_complete) {
+        if (n) {
+            /* Command did not complete immediately so disconnect.  */
+            lsi_add_msg_byte(s, 2); /* SAVE DATA POINTER */
+            lsi_add_msg_byte(s, 4); /* DISCONNECT */
+            /* wait data */
+            lsi_set_phase(s, PHASE_MI);
+            s->msg_action = 1;
+            lsi_queue_command(s);
+        } else {
+            /* wait command complete */
+            lsi_set_phase(s, PHASE_DI);
+        }
     }
 }
 
Index: qemu/hw/scsi-generic.c
===================================================================
--- qemu.orig/hw/scsi-generic.c 2007-11-28 13:13:13.000000000 +0100
+++ qemu/hw/scsi-generic.c      2007-11-28 13:13:42.000000000 +0100
@@ -496,12 +496,11 @@ static int32_t scsi_send_command(SCSIDev
             free(r->buf);
         r->buflen = 0;
         r->buf = NULL;
-        ret = execute_command(s->bdrv, r, SG_DXFER_NONE, NULL);
+        ret = execute_command(s->bdrv, r, SG_DXFER_NONE, 
scsi_command_complete);
         if (ret == -1) {
             scsi_command_complete(r, -EINVAL);
             return 0;
         }
-        scsi_command_complete(r, scsi_get_sense(r));
         return 0;
     }