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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2015-01-27 at 13:41 +0000, Stefano Stabellini wrote:
> 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>

Applied.

Sander please wrap your commit logs (the bits which aren't log
quotations at least) to <80 (ideally <75) in the future.

> 
> > --
> > 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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