[Qemu-devel] [PATCH 3/3] block: support auto-sensing of block sizes

[Christian Borntraeger]

From: Einar Lueck <address@hidden>

Virtio-blk does not impose fixed block sizes for access to
backing devices. This patch introduces support for auto
lookup of the block sizes of the backing block device. This
automatic lookup needs to be enabled explicitly. Users may
do this by specifying (physical|logical)_block_size=0.
Machine types may do this for their defaults, too.
To achieve this, a new function blkconf_blocksizes is
implemented. If physical or logical block size are zero
a corresponding ioctl tries to find an appropriate value.
If this does not work, 512 is used.

C. Borntraeger: added calls to blkconf_blocksizes for scsi and ide
to ensure that a command line parameter with blocksize == 0 will
not break scsi or IDE.

For s390-virtio-blk, this patch configures auto lookup as
default.

Signed-off-by: Einar Lueck <address@hidden>
Signed-off-by: Christian Borntraeger <address@hidden>
---
 hw/block-common.c    |   29 +++++++++++++++++++++++++++++
 hw/block-common.h    |   12 +++++++++---
 hw/ide/qdev.c        |    1 +
 hw/qdev-properties.c |    4 +++-
 hw/s390-virtio-bus.c |    2 +-
 hw/scsi-disk.c       |    1 +
 hw/virtio-blk.c      |    1 +
 7 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/hw/block-common.c b/hw/block-common.c
index f0196d7..a9c8a09 100644
--- a/hw/block-common.c
+++ b/hw/block-common.c
@@ -10,6 +10,9 @@
 #include "blockdev.h"
 #include "hw/block-common.h"
 #include "qemu-error.h"
+#ifdef __linux__
+#include <linux/fs.h>
+#endif
 
 void blkconf_serial(BlockConf *conf, char **serial)
 {
@@ -24,6 +27,32 @@ void blkconf_serial(BlockConf *conf, char **serial)
     }
 }
 
+/* Read the host block size in case the machine or the user asked for it */
+void blkconf_blocksizes(BlockConf *conf)
+{
+#ifdef __linux__
+    int block_size;
+
+    if (!conf->physical_block_size) {
+        if (bdrv_ioctl(conf->bs, BLKPBSZGET, &block_size) == 0) {
+           conf->physical_block_size = (uint16_t) block_size;
+        } else {
+            conf->physical_block_size = BLOCK_PROPERTY_STD_BLKSIZE;
+        }
+    }
+    if (!conf->logical_block_size) {
+        if (bdrv_ioctl(conf->bs, BLKSSZGET, &block_size) == 0) {
+            conf->logical_block_size = (uint16_t) block_size;
+        } else {
+            conf->logical_block_size = BLOCK_PROPERTY_STD_BLKSIZE;
+        }
+    }
+#else
+    conf->physical_block_size = BLOCK_PROPERTY_STD_BLKSIZE;
+    conf->logical_block_size  = BLOCK_PROPERTY_STD_BLKSIZE;
+#endif
+}
+
 int blkconf_geometry(BlockConf *conf, int *ptrans,
                      unsigned cyls_max, unsigned heads_max, unsigned secs_max)
 {
diff --git a/hw/block-common.h b/hw/block-common.h
index bb808f7..d593128 100644
--- a/hw/block-common.h
+++ b/hw/block-common.h
@@ -40,18 +40,23 @@ static inline unsigned int get_physical_block_exp(BlockConf 
*conf)
     return exp;
 }
 
-#define DEFINE_BLOCK_PROPERTIES(_state, _conf)                          \
+#define BLOCK_PROPERTY_STD_BLKSIZE 512
+#define DEFINE_BLOCK_PROPERTIES_EXTENDED(_state, _conf, _blksize)       \
     DEFINE_PROP_DRIVE("drive", _state, _conf.bs),                       \
     DEFINE_PROP_BLOCKSIZE("logical_block_size", _state,                 \
-                          _conf.logical_block_size, 512),               \
+                          _conf.logical_block_size, _blksize),          \
     DEFINE_PROP_BLOCKSIZE("physical_block_size", _state,                \
-                          _conf.physical_block_size, 512),              \
+                          _conf.physical_block_size, _blksize),         \
     DEFINE_PROP_UINT16("min_io_size", _state, _conf.min_io_size, 0),  \
     DEFINE_PROP_UINT32("opt_io_size", _state, _conf.opt_io_size, 0),    \
     DEFINE_PROP_INT32("bootindex", _state, _conf.bootindex, -1),        \
     DEFINE_PROP_UINT32("discard_granularity", _state, \
                        _conf.discard_granularity, 0)
 
+#define DEFINE_BLOCK_PROPERTIES(_state, _conf)                          \
+    DEFINE_BLOCK_PROPERTIES_EXTENDED(_state, _conf,                     \
+                                     BLOCK_PROPERTY_STD_BLKSIZE)
+
 #define DEFINE_BLOCK_CHS_PROPERTIES(_state, _conf)      \
     DEFINE_PROP_UINT32("cyls", _state, _conf.cyls, 0),  \
     DEFINE_PROP_UINT32("heads", _state, _conf.heads, 0), \
@@ -60,6 +65,7 @@ static inline unsigned int get_physical_block_exp(BlockConf 
*conf)
 /* Configuration helpers */
 
 void blkconf_serial(BlockConf *conf, char **serial);
+void blkconf_blocksizes(BlockConf *conf);
 int blkconf_geometry(BlockConf *conf, int *trans,
                      unsigned cyls_max, unsigned heads_max, unsigned secs_max);
 
diff --git a/hw/ide/qdev.c b/hw/ide/qdev.c
index f2e4ea4..e110caf 100644
--- a/hw/ide/qdev.c
+++ b/hw/ide/qdev.c
@@ -149,6 +149,7 @@ static int ide_dev_initfn(IDEDevice *dev, IDEDriveKind kind)
     }
 
     blkconf_serial(&dev->conf, &dev->serial);
+    blkconf_blocksizes(&dev->conf);
     if (kind != IDE_CD
         && blkconf_geometry(&dev->conf, &dev->chs_trans, 65536, 16, 255) < 0) {
         return -1;
diff --git a/hw/qdev-properties.c b/hw/qdev-properties.c
index 8aca0d4..e99dee4 100644
--- a/hw/qdev-properties.c
+++ b/hw/qdev-properties.c
@@ -904,7 +904,9 @@ static void set_blocksize(Object *obj, Visitor *v, void 
*opaque,
         error_propagate(errp, local_err);
         return;
     }
-    if (value < min || value > max) {
+
+    /* value == 0 indicates that block size should be sensed later on */
+    if ((value < min || value > max) && value > 0) {
         error_set(errp, QERR_PROPERTY_VALUE_OUT_OF_RANGE,
                   dev->id?:"", name, (int64_t)value, min, max);
         return;
diff --git a/hw/s390-virtio-bus.c b/hw/s390-virtio-bus.c
index 5849a96..223ff2d 100644
--- a/hw/s390-virtio-bus.c
+++ b/hw/s390-virtio-bus.c
@@ -401,7 +401,7 @@ static TypeInfo s390_virtio_net = {
 };
 
 static Property s390_virtio_blk_properties[] = {
-    DEFINE_BLOCK_PROPERTIES(VirtIOS390Device, blk.conf),
+    DEFINE_BLOCK_PROPERTIES_EXTENDED(VirtIOS390Device, blk.conf, 0),
     DEFINE_BLOCK_CHS_PROPERTIES(VirtIOS390Device, blk.conf),
     DEFINE_PROP_STRING("serial", VirtIOS390Device, blk.serial),
 #ifdef __linux__
diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
index 1b0afa6..29df433 100644
--- a/hw/scsi-disk.c
+++ b/hw/scsi-disk.c
@@ -2046,6 +2046,7 @@ static int scsi_initfn(SCSIDevice *dev)
     }
 
     blkconf_serial(&s->qdev.conf, &s->serial);
+    blkconf_blocksizes(&s->qdev.conf);
     if (dev->type == TYPE_DISK
         && blkconf_geometry(&dev->conf, NULL, 65535, 255, 255) < 0) {
         return -1;
diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
index e25cc96..f11ceb7 100644
--- a/hw/virtio-blk.c
+++ b/hw/virtio-blk.c
@@ -615,6 +615,7 @@ VirtIODevice *virtio_blk_init(DeviceState *dev, 
VirtIOBlkConf *blk)
     }
 
     blkconf_serial(&blk->conf, &blk->serial);
+    blkconf_blocksizes(&blk->conf);
     if (blkconf_geometry(&blk->conf, NULL, 65535, 255, 255) < 0) {
         return NULL;
     }
-- 
1.7.10.1