From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758622AbcEFTmB (ORCPT ); Fri, 6 May 2016 15:42:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:32844 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758307AbcEFTl7 (ORCPT ); Fri, 6 May 2016 15:41:59 -0400 From: Denys Vlasenko To: Jeff Kirsher Cc: Denys Vlasenko , "Ruinskiy, Dima" , intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org, LKML Subject: [PATCH] e1000e: prevent division by zero if TIMINCA is zero Date: Fri, 6 May 2016 21:41:51 +0200 Message-Id: <1462563711-30350-1-git-send-email-dvlasenk@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Users report that under VMWare, er32(TIMINCA) returns zero. This causes division by zero at init time as follows: ==> incvalue = er32(TIMINCA) & E1000_TIMINCA_INCVALUE_MASK; for (i = 0; i < E1000_MAX_82574_SYSTIM_REREADS; i++) { /* latch SYSTIMH on read of SYSTIML */ systim_next = (cycle_t)er32(SYSTIML); systim_next |= (cycle_t)er32(SYSTIMH) << 32; time_delta = systim_next - systim; temp = time_delta; ====> rem = do_div(temp, incvalue); This change makes kernel survive this, and users report that NIC does work after this change. Since on real hardware incvalue is never zero, this should not affect real hardware use case. Signed-off-by: Denys Vlasenko CC: Jeff Kirsher CC: "Ruinskiy, Dima" CC: intel-wired-lan@lists.osuosl.org CC: netdev@vger.kernel.org CC: LKML --- drivers/net/ethernet/intel/e1000e/netdev.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c index 269087c..0626935 100644 --- a/drivers/net/ethernet/intel/e1000e/netdev.c +++ b/drivers/net/ethernet/intel/e1000e/netdev.c @@ -4315,7 +4315,8 @@ static cycle_t e1000e_cyclecounter_read(const struct cyclecounter *cc) time_delta = systim_next - systim; temp = time_delta; - rem = do_div(temp, incvalue); + /* VMWare users have seen incvalue of zero, don't div / 0 */ + rem = incvalue ? do_div(temp, incvalue) : (time_delta != 0); systim = systim_next; -- 1.8.1.4