Re: [Qemu-devel] e1000 autoneg timing, piix/osx

[Gabriel L. Somlo]

On Thu, Jul 03, 2014 at 03:20:50PM +0200, Alexander Graf wrote:
> 
> On 03.07.2014, at 15:17, Gabriel L. Somlo <address@hidden> wrote:
> 
> > On Thu, Jul 03, 2014 at 10:04:55AM +0200, Alexander Graf wrote:
> >>> so Ethernet, SATA, and USB, all sharing IRQ 11. Is there an easy way
> >>> to force one of those to use a different IRQ ?
> > 
> > Oh, and on Q35, while Ethernet (and one of the USBs) is still on IRQ 11,
> > SATA ended up on IRQ 10, and things are fine there...
> > 
> >> IIRC if you plug the device in a different slot, the irq distribution
> >> should be different :).
> > 
> > Sorry for being thick, but I'm still trying to figure out if there's a
> > command-line way of making that happen. Re-ordering the "-device"
> > arguments to qemu obviously doesn't make a difference in how they're
> > assigned...
> 
> The magic word is "devfn" :). It's basically the token PCI uses to find out 
> which slot and function id a device is on. You can set "devfn" with the 
> "addr" attribute on -device.

OK. So simply doing "-device e1000-82545em,...,bus=pci.0,addr=5" to
move it up one slot from its default of "4" gets it set up with IRQ 10.
As long as it doesn't share an irq line with the SATA controller, the
network link gets detected just fine, same as on Q35.

So this is not really an autonegotiation or timing bug, it's an
unfortunate side effect of the OS X built-in proprietary e1000 driver
not playing nice when IRQs are shared with SATA in particular. At
least as far as I'm able to tell so far... :)

So I'll send out some autoneg cleanup patches after 2.1 is officially
out, but the "osx link on piix not working" mystery is solved as far
as I can tell :)

Thanks much,
--Gabriel