[Xen-devel] Re: VT-d device assignment may fail (regression from Xen c/s 19805:2f1fa2215e60)

[Weidong Han <weidong.han@xxxxxxxxx>]

Jan Beulich wrote:
> > > > On 27.10.10 at 07:43, Weidong Han <weidong.han@xxxxxxxxx> wrote:
> > > >         
> > Jan Beulich wrote:
> >     
> > > need some additional consideration, since from looking at the code
> > > I would say that reassign_device_ownership() needs some error
> > > handling improvements too: Currently, partial failure isn't being
> > > handled properly at all (respective devices are left in a half way
> > > state - no longer properly assigned to Dom0, but also not yet
> > > assigned to DomU).
> > >   
> > >       
> > Agree. The assignment should guarantee "done" or "none".
> >     
> Are you going to work on this?
>   
Not yet. I'm working on other priority tasks.
>   
> > > I also wonder what guarantee there is for a device to exist at
> > > <secbus>:00.0 (since if there is none, the same context_present()
> > > check could at least theoretically again lead to problems as it
> > > checks for pci_get_pdev() returning non-NULL
> > >   
> > > Finally, isn't it inconsistent that only the original device gets its
> > > ->domain set to the new owner and gets moved to that domain's
> > > device list, but neither the upstream bridge nor that bridge's
> > > <secbus>:00.0 get handled the same way? What if below that
> > >   
> > >       
> > Yes, it's better to do the same for the upstream bridge.
> >     
> And this?
>
>   
> > > bridge a device gets hot-added? Wouldn't that device
> > > incorrectly end up in Dom0, with no failures because the bridge
> > > still appears to be owned by Dom0 while it really isn't?
> > >   
> > >       
> > Do you want some error message for this case?
> >     
> First of all I'd want the case to be handled correctly. Only if it
> really can't be handled, I'd want an error message, yes, as
> silent failure leading to later mysterious misbehavior is very
> hard to diagnose.
>   
Agree!

Regards,
Weidong


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