Re: [Qemu-devel] [RFC PATCH v1 2/2] e1000: adjust initial autoneg timing (for piix/osx)

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jul 02, 2014 at 05:02:07AM -0400, Gabriel L. Somlo wrote:
> On Mon, Jun 30, 2014 at 08:21:43PM +0200, Alexander Graf wrote:
> > 
> > 
> > > Am 30.06.2014 um 19:55 schrieb "Michael S. Tsirkin" <mst@redhat.com>:
> > > 
> > >> On Mon, Jun 30, 2014 at 12:55:50PM -0400, Gabriel L. Somlo wrote:
> > >> When running on PIIX (as opposed to q35), the stock OS X e1000
> > >> driver (AppleIntel8254XEthernet.kext) takes longer to load and
> > >> activete, and will "miss" the link status change interrupt
> > >> injected when the emulated "hardware" autonegotiation completes
> > >> (see commit 39bb8ee737595e9b264d075dfcd7d86f4d3f1133).
> > >> 
> > >> This patch extends the delay of the autonetotiation timer set up
> > >> during set_phy_ctrl() to a value just large enough to work with
> > >> the OS X driver.
> > >> 
> > >> Signed-off-by: Gabriel Somlo <somlo@cmu.edu>
> > >> ---
> > >> 
> > >> So, the loading OS X driver must take longer between its last
> > >> write to the PHY_CTRL register and the time it starts looking
> > >> for LSC interrupts, because at delay==500 it obviously misses
> > >> the relevant interrupt. Making this 5500 (actually anything
> > >> larger than 5300, but there's a bit of variation across OS X
> > >> versions, so I rounded up a bit) has the timer fire after
> > >> enough time has passed that the driver knows what to do when
> > >> the interrupt from the network card fires...
> > >> 
> > >> Thanks,
> > >>  Gabriel
> > >> 
> > >> hw/net/e1000.c | 2 +-
> > >> 1 file changed, 1 insertion(+), 1 deletion(-)
> > >> 
> > >> diff --git a/hw/net/e1000.c b/hw/net/e1000.c
> > >> index 2376910..2300477 100644
> > >> --- a/hw/net/e1000.c
> > >> +++ b/hw/net/e1000.c
> > >> @@ -209,7 +209,7 @@ set_phy_ctrl(E1000State *s, int index, uint16_t val)
> > >>         e1000_link_down(s);
> > >>         DBGOUT(PHY, "Start link auto negotiation\n");
> > >>         timer_mod(s->autoneg_timer,
> > >> -                  qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + 500);
> > >> +                  qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + 5500);
> > >>     }
> > >> }
> > > 
> > > 
> > > Besides being a bit hacky, it actually has a decent chance
> > > to delay boot for guests. 500ms is probably the max we
> > > can reasonably tolerate, even that is a bit high.
> > 
> > Are you sure there's not just simply some irq unmasking event after 5500ms we don't handle properly?
> 
> I poked around a bit, and the e1000 interrupt mask register is NOT the
> problem (the LSC mask bit is clear at all times). If anything, maybe
> the PIIX southbridge (or something further up "north") is masking PCI
> interrupts (at least from e1000) until roughly 5500 ms into the boot
> process ? Any ideas on how I could go about verifying this (without
> access to the guest source, obviously :) ) would be very helpful...
> 
> Thanks,
> --Gabriel


Just poking around the spec I find more things
we don't implement correctly wrt to auto-negotiation.
For example, MII_SR_AUTONEG_CAPS isn't set, is it?
Maybe that's why your guest doesn't work:
it doesn't expect to get autonegotation at all?

So I have a question: does your patch actually help any guests?
If not, maybe we should defer it to after release,
and try to clean up autonegotiation more thouroughly for 2.2?


-- 
MST