From 3d05b15b03daa4e8c350a97d0d83d2c2abc8b8ef Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Fri, 6 May 2016 21:41:51 +0200 Subject: [PATCH] e1000e: prevent division by zero if TIMINCA is zero 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 Tested-by: Aaron Brown Signed-off-by: Jeff Kirsher --- 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 75e60897b7e7..9d5bab8e0e32 100644 --- a/drivers/net/ethernet/intel/e1000e/netdev.c +++ b/drivers/net/ethernet/intel/e1000e/netdev.c @@ -4352,7 +4352,8 @@ 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; -- 2.20.1