[Qemu-devel] [PATCH 2/3] scsi-disk: support WRITE SAME (16) with unmap bit

[Christoph Hellwig <hch@lst.de>]

Support discards via the WRITE SAME command with the unmap bit set, and
tell the initiator about the support for it via the block limit and the
new thin provisioning EVPD pages.  Also fix the comment which incorrectly
describedthe block limits EVPD page.

Signed-off-by: Christoph Hellwig <hch@lst.de>

Index: qemu/hw/scsi-disk.c
===================================================================
--- qemu.orig/hw/scsi-disk.c	2010-12-15 10:06:14.260003984 +0100
+++ qemu/hw/scsi-disk.c	2010-12-16 16:57:26.881003566 +0100
@@ -424,7 +424,8 @@ static int scsi_disk_emulate_inquiry(SCS
             outbuf[buflen++] = 0x80; // unit serial number
             outbuf[buflen++] = 0x83; // device identification
             if (bdrv_get_type_hint(s->bs) != BDRV_TYPE_CDROM) {
-                outbuf[buflen++] = 0xb0; // block device characteristics
+                outbuf[buflen++] = 0xb0; // block limits
+                outbuf[buflen++] = 0xb2; // thin provisioning
             }
             outbuf[pages] = buflen - pages - 1; // number of pages
             break;
@@ -466,8 +467,10 @@ static int scsi_disk_emulate_inquiry(SCS
             buflen += id_len;
             break;
         }
-        case 0xb0: /* block device characteristics */
+        case 0xb0: /* block limits */
         {
+            unsigned int unmap_sectors =
+                    s->qdev.conf.discard_granularity / s->qdev.blocksize;
             unsigned int min_io_size =
                     s->qdev.conf.min_io_size / s->qdev.blocksize;
             unsigned int opt_io_size =
@@ -492,6 +495,21 @@ static int scsi_disk_emulate_inquiry(SCS
             outbuf[13] = (opt_io_size >> 16) & 0xff;
             outbuf[14] = (opt_io_size >> 8) & 0xff;
             outbuf[15] = opt_io_size & 0xff;
+
+            /* optimal unmap granularity */
+            outbuf[28] = (unmap_sectors >> 24) & 0xff;
+            outbuf[29] = (unmap_sectors >> 16) & 0xff;
+            outbuf[30] = (unmap_sectors >> 8) & 0xff;
+            outbuf[31] = unmap_sectors & 0xff;
+            break;
+        }
+        case 0xb2: /* thin provisioning */
+        {
+            outbuf[3] = buflen = 8;
+            outbuf[4] = 0;
+            outbuf[5] = 0x40; /* write same with unmap supported */
+            outbuf[6] = 0;
+            outbuf[7] = 0;
             break;
         }
         default:
@@ -959,6 +977,12 @@ static int scsi_disk_emulate_command(SCS
             outbuf[11] = 0;
             outbuf[12] = 0;
             outbuf[13] = get_physical_block_exp(&s->qdev.conf);
+
+            /* set TPE bit if the format supports discard */
+            if (s->qdev.conf.discard_granularity) {
+                outbuf[14] = 0x80;
+            }
+
             /* Protection, exponent and lowest lba field left blank. */
             buflen = req->cmd.xfer;
             break;
@@ -1123,6 +1147,31 @@ static int32_t scsi_send_command(SCSIDev
             goto illegal_lba;
         }
         break;
+    case WRITE_SAME_16:
+        len = r->req.cmd.xfer / d->blocksize;
+
+        DPRINTF("WRITE SAME(16) (sector %" PRId64 ", count %d)\n",
+                r->req.cmd.lba, len);
+
+        if (r->req.cmd.lba > s->max_lba) {
+            goto illegal_lba;
+        }
+
+        /*
+         * We only support WRITE SAME with the unmap bit set for now.
+         */
+        if (!(buf[1] & 0x8)) {
+            goto fail;
+        }
+
+        rc = bdrv_discard(s->bs, r->req.cmd.lba * s->cluster_size,
+                          len * s->cluster_size);
+        if (rc < 0) {
+            /* XXX: better error code ?*/
+            goto fail;
+        }
+
+        break;
     default:
         DPRINTF("Unknown SCSI command (%2.2x)\n", buf[0]);
     fail:
Index: qemu/hw/scsi-defs.h
===================================================================
--- qemu.orig/hw/scsi-defs.h	2010-12-15 10:05:38.301003914 +0100
+++ qemu/hw/scsi-defs.h	2010-12-16 16:52:55.803004683 +0100
@@ -84,6 +84,7 @@
 #define MODE_SENSE_10         0x5a
 #define PERSISTENT_RESERVE_IN 0x5e
 #define PERSISTENT_RESERVE_OUT 0x5f
+#define WRITE_SAME_16         0x93
 #define MAINTENANCE_IN        0xa3
 #define MAINTENANCE_OUT       0xa4
 #define MOVE_MEDIUM           0xa5