Re: [Xen-devel] Stubdom breakage in 4.5

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Ian Campbell
> Sent: 04 February 2015 12:30
> To: Paul Durrant
> Cc: Wei Liu; xen-devel@xxxxxxxxxxxxx; Ian Jackson; Jan Beulich; Andrew
> Cooper; Stefano Stabellini
> Subject: Re: Stubdom breakage in 4.5
> 
> On Tue, 2015-02-03 at 14:11 +0000, Paul Durrant wrote:
> > How about this as a slightly hacky solution that I think may work in both
> cases?
> >
> > If Xen finds no emulator at all for an HVM guest then it waits around
> > for at least one to show up before processing an emulation request.
> > Until one does it stalls the vcpu in question indefinitely, but on the
> > first emulator attach (i.e. ioreq server creations) then the IO will
> > always be processed, even if it doesn't match the ioreq server.
> 
> It sounds plausible to me and seems like it would probably be
> backportable.
> 

Actually I think it may be even simpler, although I've not tried it. If 
hvm_domain_initialise() pauses the domain and the first 
hvm_ioreq_server_enable() unpauses it, I'm hoping that may be enough.

> Longer term I think we still need to fix the domain creation interlock
> for launching multiple qemu's, ioreq servers and any other type of
> service thing we might launch (whether in a stub dom or not), at which
> point we may be able to remove the above workaround too.
> 

Yes. Once the toolstack is aware it can keep the domain paused until all 
emulators report readiness.

  Paul

> Ian.
> 
> 

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