[PATCH AUTOSEL 4.14 14/21] net: ena: rss: store hash function as values and not bits

From: Sasha Levin
Date: Sat Feb 22 2020 - 21:27:55 EST

From: Arthur Kiyanovski <akiyano@xxxxxxxxxx>

[ Upstream commit 4844470d472d660c26149ad764da2406adb13423 ]

The device receives, stores and retrieves the hash function value as bits
and not as their enum value.

The bug:
* In ena_com_set_hash_function() we set
cmd.u.flow_hash_func.selected_func to the bit value of rss->hash_func.
(1 << rss->hash_func)
* In ena_com_get_hash_function() we retrieve the hash function and store
it's bit value in rss->hash_func. (Now the bit value of rss->hash_func
is stored in rss->hash_func instead of it's enum value)

The fix:
This commit fixes the issue by converting the retrieved hash function
values from the device to the matching enum value of the set bit using
ffs(). ffs() finds the first set bit's index in a word. Since the function
returns 1 for the LSB's index, we need to subtract 1 from the returned
value (note that BIT(0) is 1).

Fixes: 1738cd3ed342 ("net: ena: Add a driver for Amazon Elastic Network Adapters (ENA)")
Signed-off-by: Sameeh Jubran <sameehj@xxxxxxxxxx>
Signed-off-by: Arthur Kiyanovski <akiyano@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/net/ethernet/amazon/ena/ena_com.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/amazon/ena/ena_com.c b/drivers/net/ethernet/amazon/ena/ena_com.c
index c5df80f31005f..552db5399503f 100644
--- a/drivers/net/ethernet/amazon/ena/ena_com.c
+++ b/drivers/net/ethernet/amazon/ena/ena_com.c
@@ -2128,7 +2128,11 @@ int ena_com_get_hash_function(struct ena_com_dev *ena_dev,
if (unlikely(rc))
return rc;

- rss->hash_func = get_resp.u.flow_hash_func.selected_func;
+ /* ffs() returns 1 in case the lsb is set */
+ rss->hash_func = ffs(get_resp.u.flow_hash_func.selected_func);
+ if (rss->hash_func)
+ rss->hash_func--;
if (func)
*func = rss->hash_func;