Re: [Xen-devel] [PATCH v8 00/15] execute hotplug scripts from libxl

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Ian Campbell wrote:
> (resending as I don't think I had SMTP setup properly on my laptop -- sorry if 
> you get this twice!)
>
> On Wed, 2012-07-04 at 07:59 -0400, Roger Pau Monne wrote:
> > This new serie (v8) fixes a code refactoring problem that was present
> > in v7 (06/15 changed code introduced by 05/15).
>  From somewhere in here I'm seeing timeouts waiting for the b/e to go to
> state 5 when doing cd-insert on an HVM guest. I suspect because this is
> (or should be) turned into a virtual media change rather than an actual
> device remove and insert?
>
> BTW libxl_cdrom_insert hasn't been async'd up yet -- I was actually just
> looking into that when I noticed this.
>
> Ian.
>
>          ~# xl -vvv cd-insert dHVM-1 hdc /scratch/mini.iso,raw
>          libxl: debug: libxl.c:3074:libxl_device_disk_remove: ao 0x8069c30: 
> create: how=(nil) callback=(nil) poller=0x8069a50
>          libxl: debug: libxl_event.c:512:libxl__ev_xswatch_register: watch 
> w=0x8069dcc wpath=/local/domain/0/backend/qdisk/43/5632/state token=3/0: 
> register slotnum=3
>          libxl: debug: libxl.c:3074:libxl_device_disk_remove: ao 0x8069c30: 
> inprogress: poller=0x8069a50, flags=i
>          libxl: debug: libxl_event.c:457:watchfd_callback: watch w=0x8069dcc 
> wpath=/local/domain/0/backend/qdisk/43/5632/state token=3/0: event 
> epath=/local/domain/0/backend/qdisk/43/5632/state
>          libxl: debug: libxl_event.c:600:devstate_watch_callback: backend 
> /local/domain/0/backend/qdisk/43/5632/state wanted state 6 still waiting state 5
>
>          [... long wait ...]
>
>          libxl: debug: libxl_event.c:614:devstate_timeout: backend 
> /local/domain/0/backend/qdisk/43/5632/state wanted state 6  timed out
>          libxl: debug: libxl_event.c:549:libxl__ev_xswatch_deregister: watch 
> w=0x8069dcc wpath=/local/domain/0/backend/qdisk/43/5632/state token=3/0: 
> deregister slotnum=3
>          libxl: debug: libxl_event.c:561:libxl__ev_xswatch_deregister: watch 
> w=0x8069dcc: deregister unregistered
>          libxl: debug: libxl_event.c:512:libxl__ev_xswatch_register: watch 
> w=0x8069dcc wpath=/local/domain/0/backend/qdisk/43/5632/state token=3/1: 
> register slotnum=3
>          libxl: debug: libxl_event.c:457:watchfd_callback: watch w=0x8069dcc 
> wpath=/local/domain/0/backend/qdisk/43/5632/state token=3/1: event 
> epath=/local/domain/0/backend/qdisk/43/5632/state
>          libxl: debug: libxl_event.c:600:devstate_watch_callback: backend 
> /local/domain/0/backend/qdisk/43/5632/state wanted state 6 still waiting state 5
>
>          [... long wait ...]
>
>          libxl: debug: libxl_event.c:614:devstate_timeout: backend 
> /local/domain/0/backend/qdisk/43/5632/state wanted state 6  timed out
>          libxl: debug: libxl_event.c:549:libxl__ev_xswatch_deregister: watch 
> w=0x8069dcc wpath=/local/domain/0/backend/qdisk/43/5632/state token=3/1: 
> deregister slotnum=3
>          libxl: debug: libxl_event.c:561:libxl__ev_xswatch_deregister: watch 
> w=0x8069dcc: deregister unregistered
>          libxl: debug: libxl_device.c:759:device_backend_callback: unable to 
> disconnect device with path /local/domain/0/backend/qdisk/43/5632
>          libxl: debug: libxl_event.c:1434:libxl__ao_complete: ao 0x8069c30: 
> complete, rc=0
>          libxl: debug: libxl_event.c:1406:libxl__ao__destroy: ao 0x8069c30: 
> destroy
>          libxl: debug: libxl.c:1958:libxl_device_disk_add: ao 0x8069c30: 
> create: how=(nil) callback=(nil) poller=0x8069a50
>          libxl: debug: libxl_device.c:255:libxl__device_disk_set_backend: Disk 
> vdev=hdc spec.backend=unknown
>          libxl: debug: libxl_device.c:258:libxl__device_disk_set_backend:      
> format=raw cdrom=yes
>          libxl: debug: libxl_device.c:209:disk_try_backend: Disk vdev=hdc, 
> backend phy unsuitable as phys path not a block device
>          libxl: debug: libxl_device.c:216:disk_try_backend: Disk vdev=hdc, 
> backend tap unsuitable because blktap not available
>          libxl: debug: libxl_device.c:293:libxl__device_disk_set_backend: Disk 
> vdev=hdc, using backend qdisk
>          libxl: debug: libxl_event.c:1434:libxl__ao_complete: ao 0x8069c30: 
> complete, rc=0
>          libxl: debug: libxl.c:1971:libxl_device_disk_add: ao 0x8069c30: 
> inprogress: poller=0x8069a50, flags=ic
>          libxl: debug: libxl_event.c:1406:libxl__ao__destroy: ao 0x8069c30: 
> destroy
>          xc: debug: hypercall buffer: total allocations:2 total releases:2
>          xc: debug: hypercall buffer: current allocations:0 maximum 
> allocations:2
>          xc: debug: hypercall buffer: cache current size:1
>          xc: debug: hypercall buffer: cache hits:0 misses:1 toobig:1
Yes, this is due to the fact that Qemu (traditional at least) doesn't 
honour the connection/disconnection protocol, so neither removing the 
frontend or setting the backend to "closing" (5), will make Qemu 
disconnect the device. I used to have a special "dev->backend_type == 
QDISK" to skip the waiting, I've added it to my series again, and it 
should solve the waiting problem.
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