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From: David Gibson <david@gibson.dropbear.id.au>
To: Greg Kurz <groug@kaod.org>
Cc: "Alexey Kardashevskiy" <aik@ozlabs.ru>,
	"Jason Wang" <jasowang@redhat.com>,
	"Riku Voipio" <riku.voipio@iki.fi>,
	qemu-devel@nongnu.org, "Laurent Vivier" <laurent@vivier.eu>,
	"Alex Williamson" <alex.williamson@redhat.com>,
	qemu-ppc@nongnu.org, clg@kaod.org,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Marc-André Lureau" <marcandre.lureau@redhat.com>,
	philmd@redhat.com
Subject: Re: [PATCH v4 19/19] spapr: Work around spurious warnings from vfio INTx initialization
Date: Thu, 10 Oct 2019 13:02:39 +1100	[thread overview]
Message-ID: <20191010020239.GD28552@umbus.fritz.box> (raw)
In-Reply-To: <20191009191639.4055f811@bahia.lan>

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On Wed, Oct 09, 2019 at 07:16:39PM +0200, Greg Kurz wrote:
> On Wed, 9 Oct 2019 19:52:59 +1100
> David Gibson <david@gibson.dropbear.id.au> 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 <david@gibson.dropbear.id.au> 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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  reply	other threads:[~2019-10-10  2:07 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-09  6:07 [PATCH v4 00/19] spapr: IRQ subsystem cleanup David Gibson
2019-10-09  6:08 ` [PATCH v4 01/19] xive: Make some device types not user creatable David Gibson
2019-10-09  6:08 ` [PATCH v4 02/19] xics: " David Gibson
2019-10-09  6:08 ` [PATCH v4 03/19] target/ppc: Fix for optimized vsl/vsr instructions David Gibson
2019-10-09  6:08 ` [PATCH v4 04/19] spapr, xics, xive: Introduce SpaprInterruptController QOM interface David Gibson
2019-10-09  6:08 ` [PATCH v4 05/19] spapr, xics, xive: Move cpu_intc_create from SpaprIrq to SpaprInterruptController David Gibson
2019-10-09  6:08 ` [PATCH v4 06/19] spapr, xics, xive: Move irq claim and free " David Gibson
2019-10-09  6:08 ` [PATCH v4 07/19] spapr: Formalize notion of active interrupt controller David Gibson
2019-10-09  9:16   ` Cédric Le Goater
2019-10-09  9:19   ` Cédric Le Goater
2019-10-09 11:38     ` David Gibson
2019-10-09  6:08 ` [PATCH v4 08/19] spapr, xics, xive: Move set_irq from SpaprIrq to SpaprInterruptController David Gibson
2019-10-09  9:18   ` Cédric Le Goater
2019-10-09  6:08 ` [PATCH v4 09/19] spapr, xics, xive: Move print_info " David Gibson
2019-10-09  9:19   ` Cédric Le Goater
2019-10-09  6:08 ` [PATCH v4 10/19] spapr, xics, xive: Move dt_populate " David Gibson
2019-10-09  9:20   ` Cédric Le Goater
2019-10-09  6:08 ` [PATCH v4 11/19] spapr, xics, xive: Match signatures for XICS and XIVE KVM connect routines David Gibson
2019-10-09  6:08 ` [PATCH v4 12/19] spapr: Remove SpaprIrq::init_kvm hook David Gibson
2019-10-09  6:08 ` [PATCH v4 13/19] spapr, xics, xive: Move SpaprIrq::reset hook logic into activate/deactivate David Gibson
2019-10-09 14:25   ` Greg Kurz
2019-10-09 15:56     ` Cédric Le Goater
2019-10-09 15:56   ` Cédric Le Goater
2019-10-09  6:08 ` [PATCH v4 14/19] spapr, xics, xive: Move SpaprIrq::post_load hook to backends David Gibson
2019-10-09 15:57   ` Cédric Le Goater
2019-10-09  6:08 ` [PATCH v4 15/19] spapr: Remove SpaprIrq::nr_msis David Gibson
2019-10-09 15:59   ` Cédric Le Goater
2019-10-10  1:56     ` David Gibson
2019-10-09  6:08 ` [PATCH v4 16/19] spapr: Move SpaprIrq::nr_xirqs to SpaprMachineClass David Gibson
2019-10-09 16:01   ` Cédric Le Goater
2019-10-09  6:08 ` [PATCH v4 17/19] spapr: Remove last pieces of SpaprIrq David Gibson
2019-10-09 16:44   ` Cédric Le Goater
2019-10-10  1:59     ` David Gibson
2019-10-09 17:02   ` Greg Kurz
2019-10-10  2:02     ` David Gibson
2019-10-10  6:29       ` Greg Kurz
2019-10-10 20:33         ` Greg Kurz
2019-10-11  5:07           ` David Gibson
2019-10-11  6:13             ` Greg Kurz
2019-10-11  8:33               ` Greg Kurz
2019-10-12  0:00               ` David Gibson
2019-10-14  9:15                 ` Greg Kurz
2019-11-20  5:38                   ` David Gibson
2019-11-20  8:36                     ` Greg Kurz
2019-10-09  6:08 ` [PATCH v4 18/19] spapr: Handle irq backend changes with VFIO PCI devices David Gibson
2019-10-09  8:57   ` David Gibson
2019-10-09  6:08 ` [PATCH v4 19/19] spapr: Work around spurious warnings from vfio INTx initialization David Gibson
2019-10-09  8:37   ` Greg Kurz
2019-10-09  8:52     ` David Gibson
2019-10-09 17:16       ` Greg Kurz
2019-10-10  2:02         ` David Gibson [this message]
2019-10-09  9:02 ` [PATCH v4 00/19] spapr: IRQ subsystem cleanup David Gibson
2019-10-16 16:04 ` Greg Kurz
2019-10-17  0:26   ` David Gibson

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