Re: [Xen-devel] ioreq server regression

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 12/12/16 16:22, Paul Durrant wrote:
>> -----Original Message-----
>> From: Boris Ostrovsky [mailto:boris.ostrovsky@xxxxxxxxxx]
>> Sent: 12 December 2016 16:02
>> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; Jan Beulich
>> <jbeulich@xxxxxxxx>; Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>;
>> Juergen Gross <jgross@xxxxxxxx>; xen-devel <xen-devel@xxxxxxxxxxxxx>
>> Cc: zhangchen.fnst@xxxxxxxxxxxxxx
>> Subject: ioreq server regression
>>
>> Looks like commit e7dabe59c ("x86/hvm: don't unconditionally create a
>> default ioreq server") breaks restore for HVM guests.
>>
>> I see "qemu: hardware error: Invalid ioreq type 0x53" in qemu log.
>>
> Damn, yes that will be the case when migrating with legacy QEMU... we're 
> going to need another flag that's set on the domain by the restore code so 
> that the default server also gets created on restore.

I don't understand why the existing code doesn't suffice.  A domain
being restored is conceptually no different from one which is still
being constructed.

The creation_finished flag should still be clear at this point during
restore.  Is it perhaps something else doing a pause/unpause on the
domain before qemu starts up?  The creation_finished flag should only be
set at the first point the refcount goes to zero, not the first unpause
hypercall.

~Andrew

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