From 02fda01c3024463e561820afb0ba09daba4014d9 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Wed, 14 Mar 2012 15:57:05 +0000 Subject: qdev: add blocksize property type Storage interfaces like virtio-blk can be configured with block size information so that the guest can take advantage of efficient I/O request sizes. According to the SCSI Block Commands (SBC) standard a device's block size is "almost always greater than one byte and may be a multiple of 512 bytes". QEMU currently has a 512 byte minimum block size because the block layer functions work at that granularity. Furthermore, the block size should be a power of 2 because QEMU calculates bitmasks from the value. Introduce a "blocksize" property type so devices can enforce these constraints on block size values. If the constraints are relaxed in the future then this property can be updated. Introduce the new PropertyValueNotPowerOf2 QError so QMP clients know exactly why a block size value was rejected. Signed-off-by: Stefan Hajnoczi Reviewed-by: Paolo Bonzini Signed-off-by: Kevin Wolf --- hw/qdev-properties.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) (limited to 'hw/qdev-properties.c') diff --git a/hw/qdev-properties.c b/hw/qdev-properties.c index bff9152df5..98dd06aeba 100644 --- a/hw/qdev-properties.c +++ b/hw/qdev-properties.c @@ -877,6 +877,52 @@ PropertyInfo qdev_prop_pci_devfn = { .max = 0xFFFFFFFFULL, }; +/* --- blocksize --- */ + +static void set_blocksize(Object *obj, Visitor *v, void *opaque, + const char *name, Error **errp) +{ + DeviceState *dev = DEVICE(obj); + Property *prop = opaque; + int16_t *ptr = qdev_get_prop_ptr(dev, prop); + Error *local_err = NULL; + int64_t value; + + if (dev->state != DEV_STATE_CREATED) { + error_set(errp, QERR_PERMISSION_DENIED); + return; + } + + visit_type_int(v, &value, name, &local_err); + if (local_err) { + error_propagate(errp, local_err); + return; + } + if (value < prop->info->min || value > prop->info->max) { + error_set(errp, QERR_PROPERTY_VALUE_OUT_OF_RANGE, + dev->id?:"", name, value, prop->info->min, + prop->info->max); + return; + } + + /* We rely on power-of-2 blocksizes for bitmasks */ + if ((value & (value - 1)) != 0) { + error_set(errp, QERR_PROPERTY_VALUE_NOT_POWER_OF_2, + dev->id?:"", name, value); + return; + } + + *ptr = value; +} + +PropertyInfo qdev_prop_blocksize = { + .name = "blocksize", + .get = get_int16, + .set = set_blocksize, + .min = 512, + .max = 65024, +}; + /* --- public helpers --- */ static Property *qdev_prop_walk(Property *props, const char *name) -- cgit v1.2.3