Re: [Xen-devel] [RFC / PATCH] libxl: Prevent qemu closing QMP socket on shutdown before libxl is done with it.

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

Monday, January 26, 2015, 1:12:16 PM, you wrote:

> On Thu, 22 Jan 2015, Sander Eikelenboom wrote:
>> While this fixes the race and error on shutdown of a HVM guest with 
>> pci-passthrough,
>> i don't know if this could give problems in other areas (migration ?),
>> hence posted as RFC.

> I think the patch should be OK. Maybe you could test it with local
> migration (migrating a guest to localhost) and tell us if everything is
> OK?

Hi stefano,

I'm not too experienced with migration, but a simple:
"xl -v migrate domid localhost" still seems to work with this patch.

--
Sander

> If so, I think it should be committed.


>> --
>> Sander
>> 
>> 8< -----------
>> At present on shutdown when using pci-passthrough with qemu-xen, qemu closes 
>> the QMP
>> socket before libxl is done with it causing these errors to be logged by 
>> libxl:
>> 
>>     Waiting for domain test (domid 1) to die [pid 11568]
>>     Domain 1 has shut down, reason code 0 0x0
>>     Action for shutdown reason code 0 is destroy
>>     Domain 1 needs to be cleaned up: destroying the domain
>>     libxl: error: libxl_qmp.c:443:qmp_next: Socket read error: Connection 
>> reset by peer
>>     libxl: error: libxl_qmp.c:701:libxl__qmp_initialize: Failed to connect 
>> to QMP
>>     libxl: error: libxl_qmp.c:686:libxl__qmp_initialize: Connection error: 
>> Connection refused
>>     libxl: error: libxl_dm.c:1588:kill_device_model: Device Model already 
>> exited
>>     Done. Exiting now
>> 
>> Prevent this by using the qemu '-no-shutdown' parameter which is described 
>> as doing:
>>     "Donât exit QEMU on guest shutdown, but instead only stop the emulation.
>>      This allows for instance switching to monitor to commit changes to the 
>> disk image."
>> 
>> So Qemu will stop emulating, but keeps the QMP socket open and waits for 
>> libxl to
>> kill the qemu process when it is done, preventing the race and resulting in 
>> this
>> to be logged by libxl:
>> 
>>     Waiting for domain test (domid 1) to die [pid 10859]
>>     Domain 1 has shut down, reason code 0 0x0
>>     Action for shutdown reason code 0 is destroy
>>     Domain 1 needs to be cleaned up: destroying the domain
>>     Done. Exiting now
>> 
>> Signed-off-by: Sander Eikelenboom <linux@xxxxxxxxxxxxxx>
>> ---
>>  tools/libxl/libxl_dm.c |    1 +
>>  1 file changed, 1 insertion(+)
>> 
>> diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
>> index fc3f5a7..3152c87 100644
>> --- a/tools/libxl/libxl_dm.c
>> +++ b/tools/libxl/libxl_dm.c
>> @@ -435,6 +435,7 @@ static char ** 
>> libxl__build_device_model_args_new(libxl__gc *gc,
>>                                      "path=%s/qmp-libxl-%d,server,nowait",
>>                                      libxl__run_dir_path(), guest_domid));
>>  
>> +    flexarray_append(dm_args, "-no-shutdown");
>>      flexarray_append(dm_args, "-mon");
>>      flexarray_append(dm_args, "chardev=libxl-cmd,mode=control");
>>  
>> -- 
>> 1.7.10.4
>> 


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel