Re: [PATCH v2,net] hv_netvsc: Fix tx_table init in rndis_set_subchannel()

From: Jakub Kicinski
Date: Sun Dec 15 2019 - 13:52:26 EST


On Sun, 15 Dec 2019 09:11:20 -0800, Stephen Hemminger wrote:
> > > On Wed, 11 Dec 2019 14:26:27 -0800, Haiyang Zhang wrote:
> > > > Host can provide send indirection table messages anytime after RSS is
> > > > enabled by calling rndis_filter_set_rss_param(). So the host provided
> > > > table values may be overwritten by the initialization in
> > > > rndis_set_subchannel().
> > > >
> > > > To prevent this problem, move the tx_table initialization before calling
> > > > rndis_filter_set_rss_param().
> > > >
> > > > Fixes: a6fb6aa3cfa9 ("hv_netvsc: Set tx_table to equal weight after
> > > subchannels open")
> > > > Signed-off-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> > >
> > > Applied, but there are two more problems with this code:
> > > - you should not reset the indirection table if it was configured by
> > > the user to something other than the default (use the
> > > netif_is_rxfh_configured() helper to check for that)
> >
> > For Send indirection table (tx_table) ethtool doesn't have the option
> > to set it, and it's usually provided by the host. So we always initialize
> > it...
> > But, yes, for Receive indirection table (rx_table), I will make a fix, so
> > it will be set to default only for new devices, or changing the number
> > of channels; otherwise it will remain the same during operations like
> > changing MTU, ringparam.

Thank you!

> > > - you should use the ethtool_rxfh_indir_default() wrapper
> > For rx_table, we already use it:
> > rndis_device->rx_table[i] = ethtool_rxfh_indir_default(
> > For tx_table, I know it's the same operation (%, mod), but this wrapper
> > function's name is for rx_table. Should we use it for tx_table too?
> >
> > >
> > > Please fix the former problem in the net tree, and after net is merged
> > > into linux/master and net-next in a week or two please follow up with
> > > the fix for the latter for net-next.
> >
> > Sure.
> >
> > Thanks,
> > - Haiyang
> >
> As Haiyang said, this send indirection table is unique to Hyper-V it is not part of
> any of the other device models. It is not supported by ethtool. It would not be
> appropriate to repurpose the existing indirection tool; the device already uses
> the receive indirection table for RSS.

I see, I got confused by the use of the term RSS.