[Qemu-devel] [PATCH] [STABLE] Fix virtio-blk hot add after remove

[Anthony Liguori]

qdev_init_bdrv() expects that each drive added is the next logical unit for
the given interface type.  However, when dealing with hotplug, there may
be holes in the units.  drive_init reclaims holes in units but qdev_init_bdrv()
is not smart enough to do this.

Fortunately, in master, this has all been rewritten so for stable, let's hack
around this a bit.  To fix this, we need to tell qdev that a device has been
removed so that it can keep track of which units are allocated.  The only way
we can get a hook for this though is to attach to the pci uninit callback.  In
order for virtio-blk to get this, another uninit callback needs to be added to
the virtio layer.

Suggestions for a less ugly solution are appreciated.

This fixes https://bugs.launchpad.net/bugs/419590

Signed-off-by: Anthony Liguori <address@hidden>
---
 hw/qdev.c       |   33 ++++++++++++++++++++++++++++++---
 hw/virtio-blk.c |    8 ++++++++
 hw/virtio-pci.c |   19 ++++++++++++++++++-
 hw/virtio.h     |    1 +
 sysemu.h        |    2 ++
 5 files changed, 59 insertions(+), 4 deletions(-)

diff --git a/hw/qdev.c b/hw/qdev.c
index faecc76..af60e3e 100644
--- a/hw/qdev.c
+++ b/hw/qdev.c
@@ -181,21 +181,48 @@ void qdev_get_macaddr(DeviceState *dev, uint8_t *macaddr)
     memcpy(macaddr, dev->nd->macaddr, 6);
 }
 
-static int next_block_unit[IF_COUNT];
+typedef struct BlockUnitState
+{
+    BlockDriverState *bs[32];
+} BlockUnitState;
+static BlockUnitState next_block_unit[IF_COUNT];
 
 /* Get a block device.  This should only be used for single-drive devices
    (e.g. SD/Floppy/MTD).  Multi-disk devices (scsi/ide) should use the
    appropriate bus.  */
 BlockDriverState *qdev_init_bdrv(DeviceState *dev, BlockInterfaceType type)
 {
-    int unit = next_block_unit[type]++;
+    BlockDriverState *bs;
+    int unit;
     int index;
 
+    unit = 0;
+    while (next_block_unit[type].bs[unit]) {
+        unit++;
+    }
+
     index = drive_get_index(type, 0, unit);
     if (index == -1) {
         return NULL;
     }
-    return drives_table[index].bdrv;
+
+    bs = drives_table[index].bdrv;
+    next_block_unit[type].bs[unit] = bs;
+
+    return bs;
+}
+
+void qdev_uninit_bdrv(BlockDriverState *bs, BlockInterfaceType type)
+{
+    int unit;
+
+    for (unit = 0; unit < 32; unit++) {
+        if (next_block_unit[type].bs[unit] == bs) {
+            break;
+        }
+    }
+
+    next_block_unit[type].bs[unit] = NULL;
 }
 
 BusState *qdev_get_child_bus(DeviceState *dev, const char *name)
diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
index 5036b5b..4bc11e6 100644
--- a/hw/virtio-blk.c
+++ b/hw/virtio-blk.c
@@ -414,6 +414,13 @@ static int virtio_blk_load(QEMUFile *f, void *opaque, int 
version_id)
     return 0;
 }
 
+static void virtio_blk_uninit(VirtIODevice *vdev)
+{
+    VirtIOBlock *s = to_virtio_blk(vdev);
+
+    qdev_uninit_bdrv(s->bs, IF_VIRTIO);
+}
+
 VirtIODevice *virtio_blk_init(DeviceState *dev)
 {
     VirtIOBlock *s;
@@ -430,6 +437,7 @@ VirtIODevice *virtio_blk_init(DeviceState *dev)
     s->vdev.get_config = virtio_blk_update_config;
     s->vdev.get_features = virtio_blk_get_features;
     s->vdev.reset = virtio_blk_reset;
+    s->vdev.uninit = virtio_blk_uninit;
     s->bs = bs;
     s->rq = NULL;
     if (strlen(ps = (char *)drive_get_serial(bs)))
diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
index 703f4fe..00b3998 100644
--- a/hw/virtio-pci.c
+++ b/hw/virtio-pci.c
@@ -375,6 +375,22 @@ static const VirtIOBindings virtio_pci_bindings = {
     .load_queue = virtio_pci_load_queue,
 };
 
+static int virtio_pci_uninit(PCIDevice *pci_dev)
+{
+    VirtIOPCIProxy *proxy = container_of(pci_dev, VirtIOPCIProxy, pci_dev);
+    VirtIODevice *vdev = proxy->vdev;
+
+    if (vdev->uninit) {
+        vdev->uninit(vdev);
+    }
+
+    if (vdev->nvectors) {
+        return msix_uninit(pci_dev);
+    }
+
+    return 0;
+}
+
 static void virtio_init_pci(VirtIOPCIProxy *proxy, VirtIODevice *vdev,
                             uint16_t vendor, uint16_t device,
                             uint16_t class_code, uint8_t pif)
@@ -407,10 +423,11 @@ static void virtio_init_pci(VirtIOPCIProxy *proxy, 
VirtIODevice *vdev,
                          PCI_ADDRESS_SPACE_MEM,
                          msix_mmio_map);
         proxy->pci_dev.config_write = virtio_write_config;
-        proxy->pci_dev.unregister = msix_uninit;
     } else
         vdev->nvectors = 0;
 
+    proxy->pci_dev.unregister = virtio_pci_uninit;
+
     size = VIRTIO_PCI_REGION_SIZE(&proxy->pci_dev) + vdev->config_len;
     if (size & (size-1))
         size = 1 << qemu_fls(size);
diff --git a/hw/virtio.h b/hw/virtio.h
index aa55677..330b317 100644
--- a/hw/virtio.h
+++ b/hw/virtio.h
@@ -103,6 +103,7 @@ struct VirtIODevice
     void (*get_config)(VirtIODevice *vdev, uint8_t *config);
     void (*set_config)(VirtIODevice *vdev, const uint8_t *config);
     void (*reset)(VirtIODevice *vdev);
+    void (*uninit)(VirtIODevice *vdev);
     VirtQueue *vq;
     const VirtIOBindings *binding;
     void *binding_opaque;
diff --git a/sysemu.h b/sysemu.h
index ce25109..18f610b 100644
--- a/sysemu.h
+++ b/sysemu.h
@@ -193,6 +193,8 @@ extern const char *drive_get_serial(BlockDriverState *bdrv);
 extern BlockInterfaceErrorAction drive_get_onerror(BlockDriverState *bdrv);
 
 BlockDriverState *qdev_init_bdrv(DeviceState *dev, BlockInterfaceType type);
+void qdev_uninit_bdrv(BlockDriverState *bs, BlockInterfaceType type);
+
 
 struct drive_opt {
     const char *file;
-- 
1.6.2.5