Subject: Re: [PATCH 2/4] Ethtool: convert get_sg/set_sg calls to hw_features flag

From: "Matt Carlson" <[email-masked]>
Date: Wed, 3 Nov 2010 15:42:47 -0700

On Wed, Nov 03, 2010 at 03:29:10PM -0700, Micha?? Miros??aw wrote:
> On Mon, Nov 01, 2010 at 07:24:38PM -0700, Matt Carlson wrote:
> > On Fri, Oct 29, 2010 at 09:28:26PM -0700, Micha?? Miros??aw wrote:
> > > diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
> > > index 30ccbb6..b07e2d1 100644
> > > --- a/drivers/net/tg3.c
> > > +++ b/drivers/net/tg3.c
> > > @@ -11306,7 +11306,6 @@ static const struct ethtool_ops tg3_ethtool_ops = {
> > >         .get_rx_csum            = tg3_get_rx_csum,
> > >         .set_rx_csum            = tg3_set_rx_csum,
> > >         .set_tx_csum            = tg3_set_tx_csum,
> > > -       .set_sg                 = ethtool_op_set_sg,
> > >         .set_tso                = tg3_set_tso,
> > >         .self_test              = tg3_self_test,
> > >         .get_strings            = tg3_get_strings,
> > > @@ -14681,6 +14680,7 @@ static int __devinit tg3_init_one(struct pci_dev *pdev,
> > >         tp->rx_pending = TG3_DEF_RX_RING_PENDING;
> > >         tp->rx_jumbo_pending = TG3_DEF_RX_JUMBO_RING_PENDING;
> > > 
> > > +       dev->hw_features |= NETIF_F_SG;
> > Scatter-gather should not be enabled if TG3_FLAG_BROKEN_CHECKSUMS is set.  I
> > would do the following instead:
> > 
> > 	if (!(tp->tg3_flags & TG3_FLAG_BROKEN_CHECKSUMS))
> > 		dev->hw_features |= NETIF_F_SG;
> > 
> > TG3_FLAG_BROKEN_CHECKSUMS is set in tg3_get_invariants(), so this code
> > would need to be placed later than that function call.
> 
> This bug is there now, so I'll queue this as all other hints of existent
> bugs that this patch series "uncovers".

How so?  This patch would be introducing the bug.  From tg3_get_invariants:

	if (tp->pci_chip_rev_id == CHIPREV_ID_5700_B0)
		tp->tg3_flags |= TG3_FLAG_BROKEN_CHECKSUMS;
	else {
		unsigned long features = NETIF_F_IP_CSUM | NETIF_F_SG | NETIF_F_GRO;

		tp->tg3_flags |= TG3_FLAG_RX_CHECKSUMS;
		if (tp->tg3_flags3 & TG3_FLG3_5755_PLUS)
			features |= NETIF_F_IPV6_CSUM;
		tp->dev->features |= features;
		vlan_features_add(tp->dev, features);
	}