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 <dvlasenk@redhat.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Orabug: 26243014
(cherry picked from commit 3d05b15b03daa4e8c350a97d0d83d2c2abc8b8ef)
Signed-off-by: Jack Vogel <jack.vogel@oracle.com>
Reviewed-by: Ethan Zhao <ethan.zhao@oracle.com>

diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index 1ed30860b858233ff368ef6686bd64c697298f06..2795a6ff54aa3552fb12065e82afb5bbb7187c36 100644 (file)
--- 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;