[dpdk-stable] patch 'net/ixgbe/base: fix infinite recursion on PCIe link down' has been queued to LTS release 18.11.10

[Kevin Traynor]

Hi,

FYI, your patch has been queued to LTS release 18.11.10

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 08/25/20. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://github.com/kevintraynor/dpdk-stable-queue

This queued commit can be viewed at:
https://github.com/kevintraynor/dpdk-stable-queue/commit/223b828be2e333cd6ada65d79855b060c5b4a927

Thanks.

Kevin.

---
>From 223b828be2e333cd6ada65d79855b060c5b4a927 Mon Sep 17 00:00:00 2001
From: Guinan Sun <guinanx.sun at intel.com>
Date: Thu, 9 Jul 2020 08:00:31 +0000
Subject: [PATCH] net/ixgbe/base: fix infinite recursion on PCIe link down

[ upstream commit 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.

Fixes: af75078fece3 ("first public release")

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>
---
 drivers/net/ixgbe/base/ixgbe_common.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ixgbe/base/ixgbe_common.c b/drivers/net/ixgbe/base/ixgbe_common.c
index 5889410f98..9e7182eb33 100644
--- a/drivers/net/ixgbe/base/ixgbe_common.c
+++ b/drivers/net/ixgbe/base/ixgbe_common.c
@@ -3778,9 +3778,9 @@ s32 ixgbe_clear_vmdq_generic(struct ixgbe_hw *hw, u32 rar, u32 vmdq)
 		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) {
-- 
2.26.2

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2020-08-20 16:26:16.862152879 +0100
+++ 0029-net-ixgbe-base-fix-infinite-recursion-on-PCIe-link-d.patch	2020-08-20 16:26:15.822324306 +0100
@@ -1 +1 @@
-From 2d04b9e856125197ec8e967471426d56ab7efcf0 Mon Sep 17 00:00:00 2001
+From 223b828be2e333cd6ada65d79855b060c5b4a927 Mon Sep 17 00:00:00 2001
@@ -5,0 +6,2 @@
+[ upstream commit 2d04b9e856125197ec8e967471426d56ab7efcf0 ]
+
@@ -33 +34,0 @@
-Cc: stable at dpdk.org
@@ -43 +44 @@
-index fec6241f5b..2d848a02b3 100644
+index 5889410f98..9e7182eb33 100644