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


From: David Gibson
Subject: Re: [PATCH 0/5] vfio/spapr: Handle changes of master irq chip for VFIO devices
Date: Fri, 22 Nov 2019 12:18:24 +1100
User-agent: Mutt/1.12.1 (2019-06-15)

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.

-- 
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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