Re: [PATCH] x86 PCI: Do not use interrupt links for devices using MSI-X

Ingo Molnar
2009-01-07T13:14:17Z

* Jesse Barnes <jbarnes@virtuousgeek.org> wrote:

> On Monday, January 5, 2009 5:04 am Ingo Molnar wrote:
> > * Rafael J. Wysocki <rjw@sisk.pl> wrote:
> > > From: Rafael J. Wysocki <rjw@sisk.pl>
> > >
> > > pcibios_enable_device() and pcibios_disable_device() don't handle
> > > IRQs for devices that have MSI enabled and it should tread the
> >
> > s/tread/treat
> >
> > > devices with MSI-X enabled in the same way.
> > >
> > > Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
> > > ---
> > > arch/x86/pci/common.c | 4 ++--
> > > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > looks good - Jesse, what do you think?
>
> Yeah, seems obviously correct, I'll queue it up.
>
> > Rafael, i'm curious is this in response to some regression/bug? Did some
> > box or driver get confused by us enabling/disabling the GSI? Some IRQ
> > flood perhaps?
> >
> > btw., there's a small observation:
> > > + if (!dev->msi_enabled && !dev->msix_enabled)
> >
> > maybe a "pci_has_gsi_irq()" wrapper would make these checks cleaner and
> > would make things more robust, should there be any new IRQ delivery method
> > be introduced in the future?
>
> pci_has_msi_irq surely? Otherwise we'll catch pretty much everything? Or did
> you mean !pci_has_gsi_irq() here instead?

Well - here the check is: "if (not MSI or MSIX)" in essence. I thought
that it might be confusing to call it _msi() as well, so we could approach
it via the inverse space: general system interrupts (GSIs) - which are
device irqs that are neither MSI nor MSIX.

But if pci_has_msi_irq() can cleanly include the MSIX portion too, that's
fine too. (MSI-X is really MSI with wider eventing capabilities but
otherwise non-GSI just as much - and we dont want to enable (or even
touch) the legacy IRQ line registers for any of them, even if they happen
to be enumerated)

Right?

Ingo