Re: [Xen-devel] [PATCH 2 of 2] mini-os: do not wait for pci backend in pcifront_scan

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Ian Campbell writes ("[PATCH 2 of 2] mini-os: do not wait for pci backend in 
pcifront_scan"):
> Even in the case where there are passthrough devices configured libxl creates
> the stubdom and waits for it to startup _before_ adding the backend. Since the
> stub domains main thread is blocked before it can write the "running" state to
> xenstore the toolstack eventually times out and kills everything.
> 
> There is already a separate pcifront thread which waits for the backend to
> appear and calls init_pcifront at the appropriate time should a backend ever
> appear.
> 
> Unfortunately I don't have any free test boxes with VT-d so I
> haven't been able to test the cases where PCI deivces are passed
> through but I obviously have tested that I can now start an HVM
> domain with stub qemu without PCI devices passed through which I
> couldn't do before so this is an improvement. This stuff is a bit
> like pushing the lump around the carpet :-/

Right.  The worry would be, surely, that this somehow breaks by
unpausing the guest before everything has been set up by the stubdom.

But I'm happy to ack this patch on the basis that it seemed to improve
things for you and should be harmless for the non-stubdom case.

Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>

(Not applying it yet as the patch floodgate is still closed pending a
test pass.)

Ian.

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