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[PATCH v4 6/9] scsi/scsi-bus: scsi_device_find: don't return unrealized
From: |
Maxim Levitsky |
Subject: |
[PATCH v4 6/9] scsi/scsi-bus: scsi_device_find: don't return unrealized devices |
Date: |
Mon, 31 Aug 2020 18:01:21 +0300 |
The device core first places a device on the bus and then realizes it.
Make scsi_device_find avoid returing such devices to avoid
races in drivers that use an iothread (currently virtio-scsi)
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1812399
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
hw/scsi/scsi-bus.c | 88 ++++++++++++++++++++++++++++------------------
1 file changed, 53 insertions(+), 35 deletions(-)
diff --git a/hw/scsi/scsi-bus.c b/hw/scsi/scsi-bus.c
index 92d412b65c..7ceae2c92b 100644
--- a/hw/scsi/scsi-bus.c
+++ b/hw/scsi/scsi-bus.c
@@ -51,6 +51,56 @@ static const TypeInfo scsi_bus_info = {
};
static int next_scsi_bus;
+static SCSIDevice *_scsi_device_find(SCSIBus *bus, int channel, int id, int
lun,
+ bool include_unrealized)
+{
+ BusChild *kid;
+ SCSIDevice *retval = NULL;
+
+ rcu_read_lock();
+
+ QTAILQ_FOREACH_RCU(kid, &bus->qbus.children, sibling) {
+ DeviceState *qdev = kid->child;
+ SCSIDevice *dev = SCSI_DEVICE(qdev);
+
+ if (dev->channel == channel && dev->id == id) {
+ if (dev->lun == lun) {
+ retval = dev;
+ goto out;
+ }
+
+ /*
+ * If we don't find exact match (channel/bus/lun),
+ * we will return the first device which matches channel/bus
+ */
+
+ if (!retval) {
+ retval = dev;
+ }
+ }
+ }
+out:
+ /*
+ * This function might run on the IO thread and we might race against
+ * main thread hot-plugging the device.
+ * We assume that as soon as .realized is set to true we can let
+ * the user access the device.
+ */
+
+ if (retval && !include_unrealized &&
+ !atomic_load_acquire(&retval->qdev.realized)) {
+ retval = NULL;
+ }
+
+ rcu_read_unlock();
+ return retval;
+}
+
+SCSIDevice *scsi_device_find(SCSIBus *bus, int channel, int id, int lun)
+{
+ return _scsi_device_find(bus, channel, id, lun, false);
+}
+
static void scsi_device_realize(SCSIDevice *s, Error **errp)
{
SCSIDeviceClass *sc = SCSI_DEVICE_GET_CLASS(s);
@@ -186,7 +236,7 @@ static void scsi_qdev_realize(DeviceState *qdev, Error
**errp)
dev->lun = 0;
}
do {
- d = scsi_device_find(bus, dev->channel, ++id, dev->lun);
+ d = _scsi_device_find(bus, dev->channel, ++id, dev->lun, true);
} while (d && d->lun == dev->lun && id < bus->info->max_target);
if (d && d->lun == dev->lun) {
error_setg(errp, "no free target");
@@ -196,7 +246,7 @@ static void scsi_qdev_realize(DeviceState *qdev, Error
**errp)
} else if (dev->lun == -1) {
int lun = -1;
do {
- d = scsi_device_find(bus, dev->channel, dev->id, ++lun);
+ d = _scsi_device_find(bus, dev->channel, dev->id, ++lun, true);
} while (d && d->lun == lun && lun < bus->info->max_lun);
if (d && d->lun == lun) {
error_setg(errp, "no free lun");
@@ -204,7 +254,7 @@ static void scsi_qdev_realize(DeviceState *qdev, Error
**errp)
}
dev->lun = lun;
} else {
- d = scsi_device_find(bus, dev->channel, dev->id, dev->lun);
+ d = _scsi_device_find(bus, dev->channel, dev->id, dev->lun, true);
assert(d);
if (d->lun == dev->lun && dev != d) {
error_setg(errp, "lun already used by '%s'", d->qdev.id);
@@ -1573,38 +1623,6 @@ static char *scsibus_get_fw_dev_path(DeviceState *dev)
qdev_fw_name(dev), d->id, d->lun);
}
-SCSIDevice *scsi_device_find(SCSIBus *bus, int channel, int id, int lun)
-{
- BusChild *kid;
- SCSIDevice *target_dev = NULL;
-
- rcu_read_lock();
-
- QTAILQ_FOREACH_RCU(kid, &bus->qbus.children, sibling) {
- DeviceState *qdev = kid->child;
- SCSIDevice *dev = SCSI_DEVICE(qdev);
-
- if (dev->channel == channel && dev->id == id) {
- if (dev->lun == lun) {
- rcu_read_unlock();
- return dev;
- }
-
- /*
- * If we don't find exact match (channel/bus/lun),
- * we will return the first device which matches channel/bus
- */
-
- if (!target_dev) {
- target_dev = dev;
- }
- }
- }
-
- rcu_read_unlock();
- return target_dev;
-}
-
/* SCSI request list. For simplicity, pv points to the whole device */
static int put_scsi_requests(QEMUFile *f, void *pv, size_t size,
--
2.26.2
- [PATCH v4 0/9] Fix scsi devices plug/unplug races w.r.t virtio-scsi iothread, Maxim Levitsky, 2020/08/31
- [PATCH v4 1/9] scsi/scsi_bus: switch search direction in scsi_device_find, Maxim Levitsky, 2020/08/31
- [PATCH v4 2/9] rcu: Implement drain_call_rcu, Maxim Levitsky, 2020/08/31
- [PATCH v4 3/9] device_core: use drain_call_rcu in in hmp_device_del/qmp_device_add, Maxim Levitsky, 2020/08/31
- [PATCH v4 4/9] device-core: use RCU for list of childs of a bus, Maxim Levitsky, 2020/08/31
- [PATCH v4 5/9] device-core: use atomic_set on .realized property, Maxim Levitsky, 2020/08/31
- [PATCH v4 7/9] scsi/scsi_bus: Add scsi_device_get, Maxim Levitsky, 2020/08/31
- [PATCH v4 8/9] virtio-scsi: use scsi_device_get, Maxim Levitsky, 2020/08/31
- [PATCH v4 9/9] scsi/scsi_bus: fix races in REPORT LUNS, Maxim Levitsky, 2020/08/31
- [PATCH v4 6/9] scsi/scsi-bus: scsi_device_find: don't return unrealized devices,
Maxim Levitsky <=