[src/trunk]: src/sys/dev/pci/ixgbe Fix infinite recursion on PCIe link down.

[msaitoh <msaitoh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/400edee9dab3
branches:  trunk
changeset: 1027199:400edee9dab3
user:      msaitoh <msaitoh%NetBSD.org@localhost>
date:      Fri Dec 10 11:25:22 2021 +0000

description:
Fix infinite recursion on PCIe link down.

  - FreeBSD: 8270b7174c48417a4d5f3effa4a4f4588205e687 or ix-3.3.14
  - DPDK:    2d04b9e856125197ec8e967471426d56ab7efcf0

    In some corner cases the functions ixgbe_clear_rar_generic and
    ixgbe_clear_vmdq_generic may call one another leading to infinite
    recursion.

    When ixgbe_clear_vmdq_generic is called with IXGBE_CLEAR_VMDQ_ALL
    flag, it's going to clear MPSAR registers, and proceed to call
    ixgbe_clear_rar_generic, which in turn will clear the RAR registers,
    and recursively call back ixgbe_clear_vmdq_generic. Normally, the
    latter would detect that MPSAR registers have already been cleared
    and terminate the recursion.

    However, when PCIe link is down, and before the driver has had the
    opportunity to shut itself down, all register reads return 0xFFFFFFFF,
    and all register writes fail silently. In such case, because
    ixgbe_clear_vmdq_generic blindly assumes that clearing MPSAR registers
    succeeded, it's going to always call ixgbe_clear_rar_generic, which
    in turn will always call back ixgbe_clear_vmdq_generic, creating
    infinite recursion.

    This patch re-reads MPSAR register values after they had been cleared.
    In case of PCIe link failure, the values read will be non-zero, which
    will terminate the recursion. On the other hand, under normal
    circumstances the value read from MPSAR registers is going to be equal
    to the value previously written, so this patch is expected not to cause
    any regressions.

  - Note that NetBSD doesn't support VMDQ.

diffstat:

 sys/dev/pci/ixgbe/ixgbe_common.c |  8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diffs (32 lines):

diff -r 7b0d2ab29465 -r 400edee9dab3 sys/dev/pci/ixgbe/ixgbe_common.c
--- a/sys/dev/pci/ixgbe/ixgbe_common.c  Fri Dec 10 11:22:41 2021 +0000
+++ b/sys/dev/pci/ixgbe/ixgbe_common.c  Fri Dec 10 11:25:22 2021 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: ixgbe_common.c,v 1.36 2021/12/10 11:22:41 msaitoh Exp $ */
+/* $NetBSD: ixgbe_common.c,v 1.37 2021/12/10 11:25:22 msaitoh Exp $ */
 
 /******************************************************************************
   SPDX-License-Identifier: BSD-3-Clause
@@ -36,7 +36,7 @@
 /*$FreeBSD: head/sys/dev/ixgbe/ixgbe_common.c 331224 2018-03-19 20:55:05Z erj $*/
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ixgbe_common.c,v 1.36 2021/12/10 11:22:41 msaitoh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ixgbe_common.c,v 1.37 2021/12/10 11:25:22 msaitoh Exp $");
 
 #include "ixgbe_common.h"
 #include "ixgbe_phy.h"
@@ -3835,11 +3835,11 @@
        if (vmdq == IXGBE_CLEAR_VMDQ_ALL) {
                if (mpsar_lo) {
                        IXGBE_WRITE_REG(hw, IXGBE_MPSAR_LO(rar), 0);
-                       mpsar_lo = 0;
+                       mpsar_lo = IXGBE_READ_REG(hw, IXGBE_MPSAR_LO(rar));
                }
                if (mpsar_hi) {
                        IXGBE_WRITE_REG(hw, IXGBE_MPSAR_HI(rar), 0);
-                       mpsar_hi = 0;
+                       mpsar_hi = IXGBE_READ_REG(hw, IXGBE_MPSAR_HI(rar));
                }
        } else if (vmdq < 32) {
                mpsar_lo &= ~(1 << vmdq);