ixgbe: Be more careful when modifying MAC filters

This change makes it so that we are much more explicit about the ordering
of updates to the receive address register (RAR) table. Prior to this patch
I believe we may have been updating the table while entries were still
active, or possibly allowing for reordering of things since we weren't
explicitly flushing writes to either the lower or upper portion of the
register prior to accessing the other half.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Reviewed-by: Shannon Nelson <shannon.nelson@oracle.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ixgbe/ixgbe_common.c

@@ -1871,7 +1871,12 @@ s32 ixgbe_set_rar_generic(struct ixgbe_hw *hw, u32 index, u8 *addr, u32 vmdq,
 	if (enable_addr != 0)
 		rar_high |= IXGBE_RAH_AV;
 
+	/* Record lower 32 bits of MAC address and then make
+	 * sure that write is flushed to hardware before writing
+	 * the upper 16 bits and setting the valid bit.
+	 */
 	IXGBE_WRITE_REG(hw, IXGBE_RAL(index), rar_low);
+	IXGBE_WRITE_FLUSH(hw);
 	IXGBE_WRITE_REG(hw, IXGBE_RAH(index), rar_high);
 
 	return 0;
@@ -1903,8 +1908,13 @@ s32 ixgbe_clear_rar_generic(struct ixgbe_hw *hw, u32 index)
 	rar_high = IXGBE_READ_REG(hw, IXGBE_RAH(index));
 	rar_high &= ~(0x0000FFFF | IXGBE_RAH_AV);
 
-	IXGBE_WRITE_REG(hw, IXGBE_RAL(index), 0);
+	/* Clear the address valid bit and upper 16 bits of the address
+	 * before clearing the lower bits. This way we aren't updating
+	 * a live filter.
+	 */
 	IXGBE_WRITE_REG(hw, IXGBE_RAH(index), rar_high);
+	IXGBE_WRITE_FLUSH(hw);
+	IXGBE_WRITE_REG(hw, IXGBE_RAL(index), 0);
 
 	/* clear VMDq pool/queue selection for this RAR */
 	hw->mac.ops.clear_vmdq(hw, index, IXGBE_CLEAR_VMDQ_ALL);