Re: [Qemu-devel] [PATCH v2] e1000: initial link negotiation on mac osx

[Stefan Hajnoczi]

On Fri, Nov 08, 2013 at 12:12:52AM +0100, Alexander Graf wrote:
> Am 07.11.2013 um 21:28 schrieb "Gabriel L. Somlo" <address@hidden>:
> 
> > Some guest operating systems' drivers (particularly Mac OS X)
> > expect the link state to be pre-initialized by an earlier
> > component such as a proprietary BIOS. This patch injects
> > additional LSC events upon PHY reset, allowing the OS X driver
> > to successfully complete initial link negotiation. This is a
> > follow-up to commit 372254c6e5c078fb13b236bb648d2b9b2b0c70f1,
> > which works around the OS X driver's failure to properly set
> > up the MAC address.
> > 
> > Signed-off-by: Gabriel Somlo <address@hidden>
> > ---
> > 
> > On Thu, Nov 07, 2013 at 08:28:47PM +0100, Paolo Bonzini wrote:
> >> Is there any way to work around this in the guest?  Such as using a
> >> UEFI driver for e1000 or something like that.
> > 
> > Currently OS X boots on top of SeaBIOS and Chameleon, neither of which
> > know anything about the e1000 hardware. On real hardware, the XNU e1000
> > driver expects the proprietary BIOS to set things up "just right", and
> > doesn't have to bother jumping through all the hoops to properly
> > initialize the hardware from scratch (after all, the XNU driver
> > developers only have to care about a limited range of carefully
> > controlled hardware).
> > 
> > In the VM/guest scenario, QEMU is the only piece that has any knowledge
> > of the e1000 hardware, so having it prep things for the guest would be
> > the path of least resistance. Using a completely different alternative
> > to SeaBIOS (one that would/could assume e1000 is present and would know
> > enough about it to configure it just right) sounds a lot less feasible.
> 
> I'm not sure I agree. We can easily modify SeaBIOS to just loop through all 
> PCI devices, look for an e1000 and initialize it far enough for XNU, no?
> 
> After all, it sounds like that's closer to the way a real Mac works.

I'd much prefer Alex's suggestion so we avoid putting guest-specific
hacks into QEMU.

If there is really no better solution, please make an "extra" behavior
disabled by default and accessible through a device property.  For
example -device e1000,xnu-preinit-hack=on.

Stefan