linux-kernel - [PATCH AUTOSEL 4.18 31/56] ice: Use order_base

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20180920024716.58490-31-alexander.levin@microsoft.com>
Date:   Thu, 20 Sep 2018 02:47:49 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Jacob Keller <jacob.e.keller@...el.com>,
        Anirudh Venkataramanan <anirudh.venkataramanan@...el.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL 4.18 31/56] ice: Use order_base_2 to calculate higher
 power of 2

From: Jacob Keller <jacob.e.keller@...el.com>

[ Upstream commit 1eb43fc754485d772b1165118a8fb80c385f0492 ]

Currently, we use a combination of ilog2 and is_power_of_2() to
calculate the next power of 2 for the qcount. This appears to be causing
a warning on some combinations of GCC and the Linux kernel:

MODPOST 1 modules
WARNING: "____ilog2_NaN" [ice.ko] undefined!

This appears to because because GCC realizes that qcount could be zero
in some circumstances and thus attempts to link against the
intentionally undefined ___ilog2_NaN function.

The order_base_2 function is intentionally defined to return 0 when
passed 0 as an argument, and thus will be safe to use here.

This not only fixes the warning but makes the resulting code slightly
cleaner, and is really what we should have used originally.

Also update the comment to make it more clear that we are rounding up,
not just incrementing the ilog2 of qcount unconditionally.

Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@...el.com>
Tested-by: Tony Brelinski <tonyx.brelinski@...el.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 drivers/net/ethernet/intel/ice/ice_main.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_main.c b/drivers/net/ethernet/intel/ice/ice_main.c
index 46b35b78e8aa..db580d41dbf9 100644
--- a/drivers/net/ethernet/intel/ice/ice_main.c
+++ b/drivers/net/ethernet/intel/ice/ice_main.c
@@ -1313,11 +1313,8 @@ static void ice_vsi_setup_q_map(struct ice_vsi *vsi, struct ice_vsi_ctx *ctxt)
 		qcount = numq_tc;
 	}

-	/* find higher power-of-2 of qcount */
-	pow = ilog2(qcount);
-
-	if (!is_power_of_2(qcount))
-		pow++;
+	/* find the (rounded up) power-of-2 of qcount */
+	pow = order_base_2(qcount);

 	for (i = 0; i < ICE_MAX_TRAFFIC_CLASS; i++) {
 		if (!(vsi->tc_cfg.ena_tc & BIT(i))) {
-- 
2.17.1