block: Add backend_defaults property

backend_defaults property allow users to control if default block
properties should be decided with backend information.

If it is off, any backend information will be discarded, which is
suitable if you plan to perform live migration to a different disk backend.

If it is on, a block device may utilize backend information more
aggressively.

By default, it is auto, which uses backend information for block
sizes and ignores the others, which is consistent with the older
versions.

Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Message-id: 20210705130458.97642-2-akihiko.odaki@gmail.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

3 files changed, 79 insertions, 4 deletions

diff --git a/hw/block/block.c b/hw/block/block.c
index 1e34573da7..d47ebf005a 100644
--- a/hw/block/block.c
+++ b/hw/block/block.c
@@ -65,24 +65,58 @@ bool blkconf_blocksizes(BlockConf *conf, Error **errp)
 {
     BlockBackend *blk = conf->blk;
     BlockSizes blocksizes;
-    int backend_ret;
+    BlockDriverState *bs;
+    bool use_blocksizes;
+    bool use_bs;
+
+    switch (conf->backend_defaults) {
+    case ON_OFF_AUTO_AUTO:
+        use_blocksizes = !blk_probe_blocksizes(blk, &blocksizes);
+        use_bs = false;
+        break;
+
+    case ON_OFF_AUTO_ON:
+        use_blocksizes = !blk_probe_blocksizes(blk, &blocksizes);
+        bs = blk_bs(blk);
+        use_bs = bs;
+        break;
+
+    case ON_OFF_AUTO_OFF:
+        use_blocksizes = false;
+        use_bs = false;
+        break;
+
+    default:
+        abort();
+    }
 
-    backend_ret = blk_probe_blocksizes(blk, &blocksizes);
     /* fill in detected values if they are not defined via qemu command line */
     if (!conf->physical_block_size) {
-        if (!backend_ret) {
+        if (use_blocksizes) {
            conf->physical_block_size = blocksizes.phys;
         } else {
             conf->physical_block_size = BDRV_SECTOR_SIZE;
         }
     }
     if (!conf->logical_block_size) {
-        if (!backend_ret) {
+        if (use_blocksizes) {
             conf->logical_block_size = blocksizes.log;
         } else {
             conf->logical_block_size = BDRV_SECTOR_SIZE;
         }
     }
+    if (use_bs) {
+        if (!conf->opt_io_size) {
+            conf->opt_io_size = bs->bl.opt_transfer;
+        }
+        if (conf->discard_granularity == -1) {
+            if (bs->bl.pdiscard_alignment) {
+                conf->discard_granularity = bs->bl.pdiscard_alignment;
+            } else if (bs->bl.request_alignment != 1) {
+                conf->discard_granularity = bs->bl.request_alignment;
+            }
+        }
+    }
 
     if (conf->logical_block_size > conf->physical_block_size) {
         error_setg(errp,
diff --git a/include/hw/block/block.h b/include/hw/block/block.h
index c172cbe65f..5902c0440a 100644
--- a/include/hw/block/block.h
+++ b/include/hw/block/block.h
@@ -19,6 +19,7 @@
 
 typedef struct BlockConf {
     BlockBackend *blk;
+    OnOffAuto backend_defaults;
     uint32_t physical_block_size;
     uint32_t logical_block_size;
     uint32_t min_io_size;
@@ -48,6 +49,8 @@ static inline unsigned int get_physical_block_exp(BlockConf *conf)
 }
 
 #define DEFINE_BLOCK_PROPERTIES_BASE(_state, _conf)                     \
+    DEFINE_PROP_ON_OFF_AUTO("backend_defaults", _state,                 \
+                            _conf.backend_defaults, ON_OFF_AUTO_AUTO),  \
     DEFINE_PROP_BLOCKSIZE("logical_block_size", _state,                 \
                           _conf.logical_block_size),                    \
     DEFINE_PROP_BLOCKSIZE("physical_block_size", _state,                \
diff --git a/tests/qemu-iotests/172.out b/tests/qemu-iotests/172.out
index d53f61d0de..4cf4d536b4 100644
--- a/tests/qemu-iotests/172.out
+++ b/tests/qemu-iotests/172.out
@@ -21,6 +21,7 @@ Testing:
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "floppy0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -48,6 +49,7 @@ Testing: -fda TEST_DIR/t.qcow2
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "floppy0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -85,6 +87,7 @@ Testing: -fdb TEST_DIR/t.qcow2
               dev: floppy, id ""
                 unit = 1 (0x1)
                 drive = "floppy1"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -96,6 +99,7 @@ Testing: -fdb TEST_DIR/t.qcow2
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "floppy0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -137,6 +141,7 @@ Testing: -fda TEST_DIR/t.qcow2 -fdb TEST_DIR/t.qcow2.2
               dev: floppy, id ""
                 unit = 1 (0x1)
                 drive = "floppy1"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -148,6 +153,7 @@ Testing: -fda TEST_DIR/t.qcow2 -fdb TEST_DIR/t.qcow2.2
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "floppy0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -190,6 +196,7 @@ Testing: -fdb
               dev: floppy, id ""
                 unit = 1 (0x1)
                 drive = "floppy1"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -201,6 +208,7 @@ Testing: -fdb
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "floppy0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -228,6 +236,7 @@ Testing: -drive if=floppy,file=TEST_DIR/t.qcow2
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "floppy0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -265,6 +274,7 @@ Testing: -drive if=floppy,file=TEST_DIR/t.qcow2,index=1
               dev: floppy, id ""
                 unit = 1 (0x1)
                 drive = "floppy1"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -276,6 +286,7 @@ Testing: -drive if=floppy,file=TEST_DIR/t.qcow2,index=1
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "floppy0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -317,6 +328,7 @@ Testing: -drive if=floppy,file=TEST_DIR/t.qcow2 -drive if=floppy,file=TEST_DIR/t
               dev: floppy, id ""
                 unit = 1 (0x1)
                 drive = "floppy1"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -328,6 +340,7 @@ Testing: -drive if=floppy,file=TEST_DIR/t.qcow2 -drive if=floppy,file=TEST_DIR/t
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "floppy0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -373,6 +386,7 @@ Testing: -drive if=none,file=TEST_DIR/t.qcow2 -device floppy,drive=none0
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "none0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -410,6 +424,7 @@ Testing: -drive if=none,file=TEST_DIR/t.qcow2 -device floppy,drive=none0,unit=1
               dev: floppy, id ""
                 unit = 1 (0x1)
                 drive = "none0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -447,6 +462,7 @@ Testing: -drive if=none,file=TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qco
               dev: floppy, id ""
                 unit = 1 (0x1)
                 drive = "none1"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -458,6 +474,7 @@ Testing: -drive if=none,file=TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qco
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "none0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -509,6 +526,7 @@ Testing: -fda TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qcow2.2 -device fl
               dev: floppy, id ""
                 unit = 1 (0x1)
                 drive = "none0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -520,6 +538,7 @@ Testing: -fda TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qcow2.2 -device fl
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "floppy0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -562,6 +581,7 @@ Testing: -fda TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qcow2.2 -device fl
               dev: floppy, id ""
                 unit = 1 (0x1)
                 drive = "none0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -573,6 +593,7 @@ Testing: -fda TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qcow2.2 -device fl
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "floppy0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -615,6 +636,7 @@ Testing: -fdb TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qcow2.2 -device fl
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "none0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -626,6 +648,7 @@ Testing: -fdb TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qcow2.2 -device fl
               dev: floppy, id ""
                 unit = 1 (0x1)
                 drive = "floppy1"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -668,6 +691,7 @@ Testing: -fdb TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qcow2.2 -device fl
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "none0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -679,6 +703,7 @@ Testing: -fdb TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.qcow2.2 -device fl
               dev: floppy, id ""
                 unit = 1 (0x1)
                 drive = "floppy1"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -730,6 +755,7 @@ Testing: -drive if=floppy,file=TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.q
               dev: floppy, id ""
                 unit = 1 (0x1)
                 drive = "none0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -741,6 +767,7 @@ Testing: -drive if=floppy,file=TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.q
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "floppy0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -783,6 +810,7 @@ Testing: -drive if=floppy,file=TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.q
               dev: floppy, id ""
                 unit = 1 (0x1)
                 drive = "none0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -794,6 +822,7 @@ Testing: -drive if=floppy,file=TEST_DIR/t.qcow2 -drive if=none,file=TEST_DIR/t.q
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "floppy0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -842,6 +871,7 @@ Testing: -drive if=none,file=TEST_DIR/t.qcow2 -global floppy.drive=none0 -device
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "none0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -909,6 +939,7 @@ Testing: -device floppy
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = ""
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -933,6 +964,7 @@ Testing: -device floppy,drive-type=120
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = ""
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -957,6 +989,7 @@ Testing: -device floppy,drive-type=144
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = ""
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -981,6 +1014,7 @@ Testing: -device floppy,drive-type=288
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = ""
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -1008,6 +1042,7 @@ Testing: -drive if=none,file=TEST_DIR/t.qcow2 -device floppy,drive=none0,drive-t
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "none0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -1045,6 +1080,7 @@ Testing: -drive if=none,file=TEST_DIR/t.qcow2 -device floppy,drive=none0,drive-t
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "none0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -1085,6 +1121,7 @@ Testing: -drive if=none,file=TEST_DIR/t.qcow2 -device floppy,drive=none0,logical
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "none0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)
@@ -1122,6 +1159,7 @@ Testing: -drive if=none,file=TEST_DIR/t.qcow2 -device floppy,drive=none0,physica
               dev: floppy, id ""
                 unit = 0 (0x0)
                 drive = "none0"
+                backend_defaults = "auto"
                 logical_block_size = 512 (512 B)
                 physical_block_size = 512 (512 B)
                 min_io_size = 0 (0 B)