diff mbox series

[v2,5/7] virtio-scsi: don't touch scsi devices that are not yet realized or about to be un-realized

Message ID 20200511160951.8733-6-mlevitsk@redhat.com (mailing list archive)
State New, archived
Headers show
Series RFC/WIP: Fix scsi devices plug/unplug races w.r.t virtio-scsi iothread | expand

Commit Message

Maxim Levitsky May 11, 2020, 4:09 p.m. UTC 
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/virtio-scsi.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

Comments

Stefan Hajnoczi May 27, 2020, 3:08 p.m. UTC | #1 
On Mon, May 11, 2020 at 07:09:49PM +0300, Maxim Levitsky wrote:
> 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/virtio-scsi.c | 19 ++++++++++++++++++-
>  1 file changed, 18 insertions(+), 1 deletion(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
diff mbox series

Patch

diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index b0f4a35f81..1cc1fc557c 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -35,13 +35,30 @@  static inline int virtio_scsi_get_lun(uint8_t *lun)
 
 static inline SCSIDevice *virtio_scsi_device_find(VirtIOSCSI *s, uint8_t *lun)
 {
+    SCSIDevice *device = NULL;
+
     if (lun[0] != 1) {
         return NULL;
     }
     if (lun[2] != 0 && !(lun[2] >= 0x40 && lun[2] < 0x80)) {
         return NULL;
     }
-    return scsi_device_find(&s->bus, 0, lun[1], virtio_scsi_get_lun(lun));
+
+    device = scsi_device_find(&s->bus, 0, lun[1], virtio_scsi_get_lun(lun));
+
+    /*
+     * 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 (!device || !atomic_load_acquire(&device->qdev.realized)) {
+        return NULL;
+    }
+
+    return device;
 }
 
 void virtio_scsi_init_req(VirtIOSCSI *s, VirtQueue *vq, VirtIOSCSIReq *req)