Re: Stubdom breakage in 4.5

[Don Slutz <dslutz@verizon.com>]

On 02/04/15 07:58, Paul Durrant wrote:
>> -----Original Message-----
>> From: Ian Campbell
>> Sent: 04 February 2015 12:30
>> To: Paul Durrant
>> Cc: Wei Liu; xen-devel@lists.xen.org; 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.
> 

You do need to keep the PVH case in mind here.

   -Don Slutz


>> 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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