Patch "powerpc/eeh: Enable IO path on permanent error" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

powerpc/eeh: Enable IO path on permanent error

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
powerpc-eeh-enable-io-path-on-permanent-error.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Gavin Shan <[email protected]>
Date: Fri, 6 Jan 2017 10:39:49 +1100
Subject: powerpc/eeh: Enable IO path on permanent error

From: Gavin Shan <[email protected]>

[ Upstream commit 387bbc974f6adf91aa635090f73434ed10edd915 ]

We give up recovery on permanent error, simply shutdown the affected devices and remove them. If the devices can't be put into quiet state, they spew more traffic that is likely to cause another unexpected EEH error. This was observed on "p8dtu2u" machine:

   0002:00:00.0 PCI bridge: IBM Device 03dc
   0002:01:00.0 Ethernet controller: Intel Corporation \
                Ethernet Controller X710/X557-AT 10GBASE-T (rev 02)
   0002:01:00.1 Ethernet controller: Intel Corporation \
                Ethernet Controller X710/X557-AT 10GBASE-T (rev 02)
   0002:01:00.2 Ethernet controller: Intel Corporation \
                Ethernet Controller X710/X557-AT 10GBASE-T (rev 02)
   0002:01:00.3 Ethernet controller: Intel Corporation \
                Ethernet Controller X710/X557-AT 10GBASE-T (rev 02)

On P8 PowerNV platform, the IO path is frozen when shutdowning the devices, meaning the memory registers are inaccessible. It is why the devices can't be put into quiet state before removing them. This fixes the issue by enabling IO path prior to putting the devices into quiet state.

---
 arch/powerpc/kernel/eeh.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

@@ -304,9 +304,17 @@ void eeh_slot_error_detail(struct eeh_pe
 	 *
 	 * For pHyp, we have to enable IO for log retrieval. Otherwise,
 	 * 0xFF's is always returned from PCI config space.
+	 *
+	 * When the @severity is EEH_LOG_PERM, the PE is going to be
+	 * removed. Prior to that, the drivers for devices included in
+	 * the PE will be closed. The drivers rely on working IO path
+	 * to bring the devices to quiet state. Otherwise, PCI traffic
+	 * from those devices after they are removed is like to cause
+	 * another unexpected EEH error.
 	 */
 	if (!(pe->type & EEH_PE_PHB)) {
-		if (eeh_has_flag(EEH_ENABLE_IO_FOR_LOG))
+		if (eeh_has_flag(EEH_ENABLE_IO_FOR_LOG) ||
+		    severity == EEH_LOG_PERM)
 			eeh_pci_enable(pe, EEH_OPT_THAW_MMIO);
 
 		/*

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/powerpc-eeh-enable-io-path-on-permanent-error.patch