netdev - Re: [PATCH V1 net-next 02/13] net: ena: avoid unnecessary admin command when RSS function set fails

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Date:   Wed, 22 Apr 2020 17:42:57 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     <sameehj@...zon.com>
Cc:     <davem@...emloft.net>, <netdev@...r.kernel.org>,
        Arthur Kiyanovski <akiyano@...zon.com>, <dwmw@...zon.com>,
        <zorik@...zon.com>, <matua@...zon.com>, <saeedb@...zon.com>,
        <msw@...zon.com>, <aliguori@...zon.com>, <nafea@...zon.com>,
        <gtzalik@...zon.com>, <netanel@...zon.com>, <alisaidi@...zon.com>,
        <benh@...zon.com>, <ndagan@...zon.com>
Subject: Re: [PATCH V1 net-next 02/13] net: ena: avoid unnecessary admin
 command when RSS function set fails

On Wed, 22 Apr 2020 17:39:41 -0700 Jakub Kicinski wrote:
> On Wed, 22 Apr 2020 08:16:17 +0000 sameehj@...zon.com wrote:
> > From: Arthur Kiyanovski <akiyano@...zon.com>
> > 
> > Currently when ena_set_hash_function() fails the hash function is
> > restored to the previous value by calling an admin command to get
> > the hash function from the device.  
> 
> I don't see how. func argument is NULL. If I'm reading the code right
> if this function is restoring anything it's restoring the rss key.

Ah, my bad, it sets the function in dev->rss, too.

Please reorganize these changes, they are very poorly split up right
now.

> > In this commit we avoid the admin command, by saving the previous
> > hash function before calling ena_set_hash_function() and using this
> > previous value to restore the hash function in case of failure of
> > ena_set_hash_function().
> > 
> > Signed-off-by: Sameeh Jubran <sameehj@...zon.com>
> > Signed-off-by: Arthur Kiyanovski <akiyano@...zon.com>
> > ---
> >  drivers/net/ethernet/amazon/ena/ena_com.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/ethernet/amazon/ena/ena_com.c b/drivers/net/ethernet/amazon/ena/ena_com.c
> > index 07b0f396d3c2..66edc86c41c9 100644
> > --- a/drivers/net/ethernet/amazon/ena/ena_com.c
> > +++ b/drivers/net/ethernet/amazon/ena/ena_com.c
> > @@ -2286,6 +2286,7 @@ int ena_com_fill_hash_function(struct ena_com_dev *ena_dev,
> >  	struct ena_admin_get_feat_resp get_resp;
> >  	struct ena_admin_feature_rss_flow_hash_control *hash_key =
> >  		rss->hash_key;
> > +	enum ena_admin_hash_functions old_func;
> >  	int rc;
> >  
> >  	/* Make sure size is a mult of DWs */
> > @@ -2325,12 +2326,13 @@ int ena_com_fill_hash_function(struct ena_com_dev *ena_dev,
> >  		return -EINVAL;
> >  	}
> >  
> > +	old_func = rss->hash_func;
> >  	rss->hash_func = func;
> >  	rc = ena_com_set_hash_function(ena_dev);
> >  
> >  	/* Restore the old function */
> >  	if (unlikely(rc))
> > -		ena_com_get_hash_function(ena_dev, NULL, NULL);
> > +		rss->hash_func = old_func;  
> 
> Please order your commits correctly.
> 
> >  	return rc;
> >  }