ixgbevf: Prevent possible race condition by checking for message

The mailbox interrupt routine might cause a race condition sometimes
and cause a message to be missed.

Signed-off-by: Greg Rose <gregory.v.rose@intel.com>
Tested-by: Sibai Li <sibai.li@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 21 insertions, 18 deletions

diff --git a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
index 891162d1610c..1cad3b6d2c30 100644
--- a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
+++ b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
@@ -917,31 +917,34 @@ static irqreturn_t ixgbevf_msix_mbx(int irq, void *data)
         struct ixgbe_hw *hw = &adapter->hw;
         u32 eicr;
         u32 msg;
+        bool got_ack = false;
 
         eicr = IXGBE_READ_REG(hw, IXGBE_VTEICS);
         IXGBE_WRITE_REG(hw, IXGBE_VTEICR, eicr);
 
-        if (!hw->mbx.ops.check_for_ack(hw)) {
-                /*
-                 * checking for the ack clears the PFACK bit.  Place
-                 * it back in the v2p_mailbox cache so that anyone
-                 * polling for an ack will not miss it.  Also
-                 * avoid the read below because the code to read
-                 * the mailbox will also clear the ack bit.  This was
-                 * causing lost acks.  Just cache the bit and exit
-                 * the IRQ handler.
-                 */
-                hw->mbx.v2p_mailbox |= IXGBE_VFMAILBOX_PFACK;
-                goto out;
-        }
+        if (!hw->mbx.ops.check_for_ack(hw))
+                got_ack = true;
 
-        /* Not an ack interrupt, go ahead and read the message */
-        hw->mbx.ops.read(hw, &msg, 1);
+        if (!hw->mbx.ops.check_for_msg(hw)) {
+                hw->mbx.ops.read(hw, &msg, 1);
 
-        if ((msg & IXGBE_MBVFICR_VFREQ_MASK) == IXGBE_PF_CONTROL_MSG)
-                mod_timer(&adapter->watchdog_timer,
-                          round_jiffies(jiffies + 1));
+                if ((msg & IXGBE_MBVFICR_VFREQ_MASK) == IXGBE_PF_CONTROL_MSG)
+                        mod_timer(&adapter->watchdog_timer,
+                                  round_jiffies(jiffies + 1));
 
+                if (msg & IXGBE_VT_MSGTYPE_NACK)
+                        pr_warn("Last Request of type %2.2x to PF Nacked\n",
+                                msg & 0xFF);
+                goto out;
+        }
+
+        /*
+         * checking for the ack clears the PFACK bit.  Place
+         * it back in the v2p_mailbox cache so that anyone
+         * polling for an ack will not miss it
+         */
+        if (got_ack)
+                hw->mbx.v2p_mailbox |= IXGBE_VFMAILBOX_PFACK;
 out:
         return IRQ_HANDLED;
 }