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

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Tue, 27 Jan 2015, Sander Eikelenboom wrote:
> 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.

Yep, that's the one.

In that case:

Acked-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>


> --
> 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
> >> 
>

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