RE: [EXTERNAL] Re: [PATCH net-next v2 02/13] net: mana: swap queue sets in mana_set_channels

> Thank you for your contribution! Sashiko AI review found 1 potential issue(s)
> to consider:
> - [Medium] mana_set_channels silently drops user-configured RSS indirection
> tables
> --
> 
> --- Patch [2]: [PATCH net-next v2 02/13] net: mana: swap queue sets in
> mana_set_channels --- commit
> 20d58255702f027247917ff013e18e0c18e9845c
> Author: Long Li <[email protected]>
> Subject: net: mana: swap queue sets in mana_set_channels
> 
> This converts the channel count path away from detach/attach. It builds the
> new queue set while the current one keeps serving traffic, then swaps it in
> and retires the old one.
> 
> > diff --git a/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
> > b/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
> > index 04b7a5c0fdabc..b12291555eaeb 100644
> > --- a/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
> > +++ b/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
> [ ... ]
> > @@ -659,42 +659,88 @@ static int mana_set_channels(struct net_device
> *ndev,
> >  	apc->channel_changing = true;
> >  	mutex_unlock(&apc->vport_mutex);
> >
> > -	err = mana_pre_alloc_rxbufs(apc, ndev->mtu, new_count);
> > -	if (err) {
> > -		netdev_err(ndev, "Insufficient memory for new allocations");
> > +	scratch = mana_qset_scratch_alloc(apc);
> > +	if (!scratch) {
> > +		err = -ENOMEM;
> >  		goto clear_flag;
> >  	}
> >
> > -	err = mana_detach(ndev, false);
> > -	if (err) {
> > -		netdev_err(ndev, "mana_detach failed: %d\n", err);
> > -		goto out;
> > -	}
> > +	err = mana_alloc_qset(scratch, new_count, apc->rx_queue_size,
> > +			      apc->tx_queue_size, apc->priv_flags, &newq);
> 
> [Severity: Medium]
> Does this silently drop a user-configured RSS indirection table?
> 
> By using mana_alloc_qset() here in mana_set_channels(), a custom RSS
> indirection table configured via ethtool will be lost. When mana_alloc_qset()
> is called, it unconditionally initializes the table with default values in
> drivers/net/ethernet/microsoft/mana/mana_en.c:
> 
> mana_alloc_qset() {
>     ...
>     mana_rss_table_init(scratch);
>     ...
>     mana_qset_snapshot(scratch, out);
> }
> 
> Because out->rxfh_indir_lost is explicitly set to false, the old indirection
> table is freed without preserving the entries, and no
> ethtool_rxfh_indir_lost() notification is sent.
> 
> Will this cause the interface to silently revert to a default hashing
> distribution after a channel count change instead of preserving it?

This is a pre-existing upstream behavior. Patch 11/13 adds  mana_rss_table_keep() and fixes it.

Long