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Re: [PATCH v4 19/19] spapr: Work around spurious warnings from vfio INTx
From: |
David Gibson |
Subject: |
Re: [PATCH v4 19/19] spapr: Work around spurious warnings from vfio INTx initialization |
Date: |
Thu, 10 Oct 2019 13:02:39 +1100 |
User-agent: |
Mutt/1.12.1 (2019-06-15) |
On Wed, Oct 09, 2019 at 07:16:39PM +0200, Greg Kurz wrote:
> On Wed, 9 Oct 2019 19:52:59 +1100
> David Gibson <address@hidden> wrote:
>
> > On Wed, Oct 09, 2019 at 10:37:38AM +0200, Greg Kurz wrote:
> > > On Wed, 9 Oct 2019 17:08:18 +1100
> > > David Gibson <address@hidden> wrote:
> > >
> > > > Traditional PCI INTx for vfio devices can only perform well if using
> > > > an in-kernel irqchip. Therefore, vfio_intx_update() issues a warning
> > > > if an in kernel irqchip is not available.
> > >
> > > Can you elaborate on what doesn't "perform well" without an
> > > in-kernel irqchip ?
> >
> > Not really, no, but Alex Williamson tells me it is soo.
> >
> > > Is it a matter of performance or is it
> > > actually broken or something else ?
> >
> > I believe it's a matter of performance, but such a big one that it
> > makes using it without kernel irqchip infeasible in many cases.
> >
> > > What is the impact on -machine accel=kvm,kernel-irqchip=off which
> > > always spit this warning ?
> >
> > It should still spit that warning.
> >
>
> Yeah of course it does, but it is expected that we cannot setup
> the irqfd since we deliberately don't have an in-kernel irqchip,
> isn't it ? Why spit a warning in this case ? Or is it just a not
> very user friendly way of saying "you will have poor performance
> if the VFIO device uses PCI INTx" ?
The last thing, AIUI.
--
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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- Re: [PATCH v4 17/19] spapr: Remove last pieces of SpaprIrq, (continued)
- [PATCH v4 11/19] spapr, xics, xive: Match signatures for XICS and XIVE KVM connect routines, David Gibson, 2019/10/09
- [PATCH v4 10/19] spapr, xics, xive: Move dt_populate from SpaprIrq to SpaprInterruptController, David Gibson, 2019/10/09
- [PATCH v4 05/19] spapr, xics, xive: Move cpu_intc_create from SpaprIrq to SpaprInterruptController, David Gibson, 2019/10/09
- [PATCH v4 06/19] spapr, xics, xive: Move irq claim and free from SpaprIrq to SpaprInterruptController, David Gibson, 2019/10/09
- [PATCH v4 19/19] spapr: Work around spurious warnings from vfio INTx initialization, David Gibson, 2019/10/09
Re: [PATCH v4 00/19] spapr: IRQ subsystem cleanup, David Gibson, 2019/10/09
Re: [PATCH v4 00/19] spapr: IRQ subsystem cleanup, Greg Kurz, 2019/10/16