linux-kernel - Re: [Xen-devel] Re: [GIT PATCH v2 0/14] xen: events: cleanups + ween off nr

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Message-ID: <1299842689.17339.1986.camel@zakaz.uk.xensource.com>
Date:	Fri, 11 Mar 2011 11:24:49 +0000
From:	Ian Campbell <Ian.Campbell@...rix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Fitzhardinge <jeremy@...p.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Stefano Stabellini <Stefano.Stabellini@...citrix.com>
Subject: Re: [Xen-devel] Re: [GIT PATCH v2 0/14] xen: events: cleanups +
 ween off nr_irqs

On Fri, 2011-03-11 at 09:12 +0000, Ian Campbell wrote:
> On Thu, 2011-03-10 at 22:57 +0000, Konrad Rzeszutek Wilk wrote:
> > On Thu, Mar 10, 2011 at 04:07:59PM +0000, Ian Campbell wrote:
> > > Changes since last time:
> > >       * correct return value of xen_irq_from_pirq
> > >       * WARN if a pirq cannot be allocated for a legacy IRQ
> > >       * Updated checking comment of "xen: events: do not workaround
> > >         too-small nr_irqs"
> > > 
> > > The following series makes a few cleanups to the Xen IRQ infrastructure.
> > > The most important thing is that it removes the need to know about
> > > nr_irqs and in particular the reliance on nr_irqs being static.
> > > 
> > > Apart from being generally a good thing this is needed because in 2.6.39
> > > nr_irqs will be able to grow dynamically, specifically e7bcecb7b1d2
> > > "genirq: Make nr_irqs runtime expandable" from tip/core/irq is targeted
> > > at 2.6.39.
> > > 
> > > Dynamically growing nr_irqs also allows us to remove the workaround
> > > which eats into GSI space if a dynamic IRQ cannot be allocated.
> > > 
> > > There is no ideal sequencing of this series vs e7bcecb7b1d2 (most should
> > > have gone in before, but the penultimate patch really needed to be
> > > simultaneous) so I haven't bothered to try and pull anything from tip
> > > into this branch -- it should all be resolved during the merge window
> > > and bisection won't be too broken since the "eat into GSI space"
> > > workaround only appears to be needed on a small number of older
> > > platforms (qemu being the main exception).
> > 
> > <nods>
> > > 
> > > I have tested:
> > >       * Domain 0 on real h/w and under qemu
> > >       * PV guest, including migration and passthrough of both VF and PF.
> > >       * PVHVM guest, including migration and passthrough of both VF and
> > >         PF.
> > 
> > I am having difficulties with passthrough of an USB device. Somehow the
> > irq count is not going up at all (both in dom0 and domU) and it looks to
> > be doing just simple polling. I've rebased the xen-pciback to be on top
> > of your changes and apply cleanly. The whole lot is now in #master
> > 
> > MSI and MSI-X devices work just fine in both Dom0 and DomU case so
> > it is something special with the legacy IRQs. Probably forgot something
> > simple...
> 
> Thanks, I'll take a look. Did you mean "legacy IRQ" as in <16 or as in
> not-MSI(-X)?

Works for me in a PV guest, at least under the second interpretation (I
don't have any useful devices IRQ < 16). This is with your pciback 0.5.

I see something like what you describe under HVM, although pciback is
not used in that case. xc_physdev_map_pirq is used but not with
the /sys/.../bdf node AFAICT.

More digging required I guess...

Ian.

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