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

["Zhai, Edwin" <edwin.zhai@xxxxxxxxx>]

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.
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.


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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