Re: [PATCH 0/5] vfio/spapr: Handle changes of master irq chip for VFIO devices

[David Gibson]

On Thu, Nov 21, 2019 at 06:28:07PM -0700, Alex Williamson wrote:
> On Fri, 22 Nov 2019 12:18:24 +1100
> David Gibson <address@hidden> wrote:
> 
> > On Thu, Nov 21, 2019 at 09:57:38AM -0700, Alex Williamson wrote:
> > > On Thu, 21 Nov 2019 11:56:02 +1100
> > > David Gibson <address@hidden> wrote:
> > >   
> > > > Due to the way feature negotiation works in PAPR (which is a
> > > > paravirtualized platform), we can end up changing the global irq chip
> > > > at runtime, including it's KVM accelerate model.  That causes
> > > > complications for VFIO devices with INTx, which wire themselves up
> > > > directly to the KVM irqchip for performance.
> > > > 
> > > > This series introduces a new notifier to let VFIO devices (and
> > > > anything else that needs to in the future) know about changes to the
> > > > master irqchip.  It modifies VFIO to respond to the notifier,
> > > > reconnecting itself to the new KVM irqchip as necessary.
> > > > 
> > > > In particular this removes a misleading (though not wholly inaccurate)
> > > > warning that occurs when using VFIO devices on a pseries machine type
> > > > guest.
> > > > 
> > > > Open question: should this go into qemu-4.2 or wait until 5.0?  It's
> > > > has medium complexity / intrusiveness, but it *is* a bugfix that I
> > > > can't see a simpler way to fix.  It's effectively a regression from
> > > > qemu-4.0 to qemu-4.1 (because that introduced XIVE support by
> > > > default), although not from 4.1 to 4.2.  
> > > 
> > > Looks reasonable to me for 4.2, the vfio changes are not as big as they
> > > appear.  If Paolo approves this week, I can send a pull request,
> > > otherwise I can leave my ack for someone else as I'll be on PTO/holiday
> > > next week.  Thanks,  
> > 
> > I'm happy to take it through my tree, and expect to be sending a PR in
> > that timescale, so an ack sounds good.
> > 
> > I've pulled the series into my ppc-for-4.2 branch tentatively.
> 
> Tested-by: Alex Williamson <address@hidden>
> Reviewed-by: Alex Williamson <address@hidden>
> Acked-by: Alex Williamson <address@hidden>

Thanks!

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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