[SRU,Cosmic,Bionic,4/6] s390/qeth: avoid using is_multicast_ether_addr_64bits on (u8 *)[6]

Message ID CA+jPhpfxdTTM12hT43DRimoGZmGBsW4woQv7X-mtdFN74=TS4w@mail.gmail.com
State New
Headers show
Series
  • Fixes for LP1797367
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Commit Message

Frank Heimes Nov. 7, 2018, 6:25 p.m.
From: Vasily Gorbik <gor@linux.ibm.com>

BugLink: http://bugs.launchpad.net/bugs/1797367

s390/qeth: avoid using is_multicast_ether_addr_64bits on (u8 *)[6]

*ether_addr*_64bits functions have been introduced to optimize
performance critical paths, which access 6-byte ethernet address as u64
value to get "nice" assembly. A harmless hack works nicely on ethernet
addresses shoved into a structure or a larger buffer, until busted by
Kasan on smth like plain (u8 *)[6].

qeth_l2_set_mac_address calls qeth_l2_remove_mac passing
u8 old_addr[ETH_ALEN] as an argument.

Adding/removing macs for an ethernet adapter is not that performance
critical. Moreover is_multicast_ether_addr_64bits itself on s390 is not
faster than is_multicast_ether_addr:

is_multicast_ether_addr(%r2) -> %r2
llc %r2,0(%r2)
risbg       %r2,%r2,63,191,0

is_multicast_ether_addr_64bits(%r2) -> %r2
llgc        %r2,0(%r2)
risbg       %r2,%r2,63,191,0

So, let's just use is_multicast_ether_addr instead of
is_multicast_ether_addr_64bits.

Fixes: bcacfcbc82b4 ("s390/qeth: fix MAC address update sequence")
Reviewed-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry-picked from commit 9d0a58fb9747afd27d490c02a97889a1b59f6be4)
Signed-off-by: Frank Heimes <frank.heimes@canonical.com>

---


@@ -157,7 +157,7 @@ static int qeth_l2_write_mac(struct qeth_card
*card, u8 *mac)

 static int qeth_l2_remove_mac(struct qeth_card *card, u8 *mac)
 {
-       enum qeth_ipa_cmds cmd = is_multicast_ether_addr_64bits(mac) ?
+       enum qeth_ipa_cmds cmd = is_multicast_ether_addr(mac) ?
                                        IPA_CMD_DELGMAC : IPA_CMD_DELVMAC;
        int rc;

Patch

diff --git a/drivers/s390/net/qeth_l2_main.c b/drivers/s390/net/qeth_l2_main.c
index 7daf125..5464515 100644
--- a/drivers/s390/net/qeth_l2_main.c
+++ b/drivers/s390/net/qeth_l2_main.c
@@ -140,7 +140,7 @@  static int qeth_l2_send_setmac(struct qeth_card
*card, __u8 *mac)

 static int qeth_l2_write_mac(struct qeth_card *card, u8 *mac)
 {
-       enum qeth_ipa_cmds cmd = is_multicast_ether_addr_64bits(mac) ?
+       enum qeth_ipa_cmds cmd = is_multicast_ether_addr(mac) ?
                                        IPA_CMD_SETGMAC : IPA_CMD_SETVMAC;
        int rc;