Re: [Qemu-block] [Qemu-devel] [PATCH v2 0/6] Acquire the AioContext during _realize()

[Alberto Garcia]

On Fri 18 Jan 2019 11:14:15 AM CET, Kevin Wolf wrote:
> There are two ways to trigger the crash even without
> x-blockdev-set-iothread:
>
> * device_del, then device_add for a device with iothread (virtio-scsi;
>   may or may not exist with virtio-blk)
>   https://bugzilla.redhat.com/show_bug.cgi?id=1656276
>
> * Simply attach two devices with iothread to the the same node
>   https://bugzilla.redhat.com/show_bug.cgi?id=1662508

While having a look at this I found another crash. Here's how to
reproduce it (wait for the events after each system_reset):

   { "execute": "qmp_capabilities" }
   { "execute": "blockdev-add", "arguments": {"driver": "null-co", "node-name": 
"hd0"}}
   { "execute": "device_add", "arguments": {"id": "vb0", "driver": 
"virtio-blk", "drive": "hd0"}}
   { "execute": "system_reset"}

   { "execute": "device_del", "arguments": {"id": "vb0"}}
   { "execute": "system_reset"}

   { "execute": "device_add", "arguments": {"id": "vb0", "driver": 
"virtio-blk", "drive": "hd0"}}
   { "execute": "system_reset"}

   { "execute": "device_del", "arguments": {"id": "vb0"}}
   { "execute": "system_reset"}

   { "execute": "device_add", "arguments": {"id": "vb0", "driver": 
"virtio-blk", "drive": "hd0"}}
   { "execute": "system_reset"}

kvm_mem_ioeventfd_add: error adding ioeventfd: No space left on device
Aborted

git-bisect points to this commit:

   commit 3ac7d43a6fbb5d4a3d01fc9a055c218030af3727
   Author: Paolo Bonzini <address@hidden>
   Date:   Wed Nov 28 17:28:45 2018 +0100

       memory: update coalesced_range on transaction_commit

       The e1000 driver calls memory_region_add_coalescing but
       kvm_coalesce_mmio_region is never called for those regions.  The bug
       dates back to the introduction of the memory region API; to fix it,
       delete and re-add coalesced MMIO ranges when building the FlatViews.
       
       Because coalesced MMIO regions apply to all address spaces, the
       has_coalesced_range flag has to be changed into an int.

Berto