On Sun, 15 Dec 2019 16:38:00 +0000
Haiyang Zhang [off-list ref] wrote:

quoted

-----Original Message-----
From: Jakub Kicinski <redacted>
Sent: Saturday, December 14, 2019 2:30 PM
To: Haiyang Zhang <haiyangz@microsoft.com>
Cc: sashal@kernel.org; linux-hyperv@vger.kernel.org; netdev@vger.kernel.org;
KY Srinivasan [off-list ref]; Stephen Hemminger
[off-list ref]; olaf@aepfle.de; vkuznets
[off-list ref]; davem@davemloft.net; linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2,net] hv_netvsc: Fix tx_table init in rndis_set_subchannel()

On Wed, 11 Dec 2019 14:26:27 -0800, Haiyang Zhang wrote:  

quoted

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")  

quoted

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>  

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.

quoted

 - 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?

quoted

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.