git: 8270b7174c48 - main - ixgbe: fix infinite recursion on PCIe link down

[Kevin Bowling]

The branch main has been updated by kbowling (ports committer):

URL: https://cgit.FreeBSD.org/src/commit/?id=8270b7174c48417a4d5f3effa4a4f4588205e687

commit 8270b7174c48417a4d5f3effa4a4f4588205e687
Author:     Guinan Sun <guinanx.sun at intel.com>
AuthorDate: 2020-07-09 08:00:31 +0000
Commit:     Kevin Bowling <kbowling at FreeBSD.org>
CommitDate: 2021-09-07 02:22:11 +0000

    ixgbe: fix infinite recursion on PCIe link down
    
    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.
    
    Signed-off-by: Robert Konklewski <robertx.konklewski at intel.com>
    Signed-off-by: Guinan Sun <guinanx.sun at intel.com>
    Reviewed-by: Wei Zhao <wei.zhao1 at intel.com>
    
    Approved by:    imp
    Obtained from:  DPDK (2d04b9e856125197ec8e967471426d56ab7efcf0)
    MFC after:      1 week
    Differential Revision:  https://reviews.freebsd.org/D31621
---
 sys/dev/ixgbe/ixgbe_common.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sys/dev/ixgbe/ixgbe_common.c b/sys/dev/ixgbe/ixgbe_common.c
index d7da9f81fbf8..92db7c14da45 100644
--- a/sys/dev/ixgbe/ixgbe_common.c
+++ b/sys/dev/ixgbe/ixgbe_common.c
@@ -3813,11 +3813,11 @@ s32 ixgbe_clear_vmdq_generic(struct ixgbe_hw *hw, u32 rar, u32 vmdq)
 	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);