Re: [Xen-devel] [PATCH] [IOEMU] Fix wrong INTx for pass-through device

[Simon Horman <horms@xxxxxxxxxxxx>]

On Tue, Dec 29, 2009 at 08:22:35AM +0800, Zhai, Edwin wrote:
> Your patch can also fix this issue, as using physical pin info for
> both guest and xen.
> Only potential issue is that guest will see a single function device
> is not linked to INTA, say assign 00:1a.7 to guest as 00:4.0. It
> should work, but seems doesn't comply with PCI spec.

I had a vague memory that was the case,
I have been meaning to check the spec.

> We have 2 options here:
> 1. always use INTA
> 2. Use INTA for virtual function 0, and physical value for others.
> Options 2 is more friendly to multiple-function device assignment,
> and is current used.

2 seems to be a much better solution to me.

Tom, could you see if Edwin's patch, without your patch, resolves
the problem that you were seeing?

> Tom Rotenberg wrote:
> >Hi,
> >
> >I ran into similar problems last week, and i tried the following fix,
> >which looks like it kind-of fixed it, does this do the same fix as
> >your patch?
> >
> >Here is the patch i used:
> >
> >--- a/tools/ioemu/hw/pass-through.c  Sun Dec 27 11:56:08 2009 +0200
> >+++ b/tools/ioemu/hw/pass-through.c  Sun Dec 27 11:56:08 2009 +0200
> >@@ -4209,8 +4209,14 @@
> >  */
> > uint8_t pci_intx(struct pt_dev *ptdev)
> > {
> > +#if 0    /* FIX */
> >      if (!PCI_FUNC(ptdev->dev.devfn))
> >          return 0;
> > +#endif /* FIX */
> > +
> >      return pci_read_intx(ptdev);
> >}
> >
> >Tom
> >
> >On Mon, Dec 28, 2009 at 9:04 AM, Zhai, Edwin <edwin.zhai@xxxxxxxxx> wrote:
> >>Simon,
> >>For the pass-through device's INTx emulation, we follow the policy: if
> >>virtual function 0, use INTA#, otherwise use hardware value. However, this
> >>policy only apply when bind_pt_pci_irq to xen, and always use physical value
> >>when exporting to guest. This discrepancy cause different INTx, thus
> >>different GSI in xen and guest, so that interrupts never got injected to
> >>guest. E.g. when assigning a USB controller with non-zero function(00:1d.2)
> >>to guest as 00:4.0, xen will see INTA#, while guest see INTC#.
> >>
> >>This simple patch can fix it. Could you pls. review it?
> >>
> >>Thanks,
> >>
> >>--
> >>best rgds,
> >>edwin
> >>
> >>
> >>Signed-Off-By: Zhai Edwin <edwin.zhai@xxxxxxxxx>
> >>
> >>diff --git a/hw/pass-through.c b/hw/pass-through.c
> >>index e7bd386..a08c0bf 100644
> >>--- a/hw/pass-through.c
> >>+++ b/hw/pass-through.c
> >>@@ -2710,7 +2710,8 @@ static uint32_t pt_status_reg_init(struct pt_dev
> >>*ptdev,
> >> static uint32_t pt_irqpin_reg_init(struct pt_dev *ptdev,
> >>        struct pt_reg_info_tbl *reg, uint32_t real_offset)
> >> {
> >>-    return ptdev->dev.config[real_offset];
> >>+    /* Translate xen INTx value to hw */
> >>+    return pci_intx(ptdev) + 1;
> >> }
> >>
> >> /* initialize BAR */
> >>
> >>_______________________________________________
> >>Xen-devel mailing list
> >>Xen-devel@xxxxxxxxxxxxxxxxxxx
> >>http://lists.xensource.com/xen-devel
> >>
> >>
> >
> 
> -- 
> best rgds,
> edwin

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