[4.2.y-ckt stable] Patch "powerpc/eeh: Restore initial state in eeh_pe_reset_and_recover()" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    powerpc/eeh: Restore initial state in eeh_pe_reset_and_recover()

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    https://git.launchpad.net/~canonical-kernel/linux/+git/linux-stable-ckt/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt12.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From a43911d82ece9c37453bc0b0d6fc16bae3d90376 Mon Sep 17 00:00:00 2001
From: Gavin Shan <gwshan at linux.vnet.ibm.com>
Date: Wed, 27 Apr 2016 11:14:51 +1000
Subject: powerpc/eeh: Restore initial state in eeh_pe_reset_and_recover()

commit 5a0cdbfd17b90a89c64a71d8aec9773ecdb20d0d upstream.

The function eeh_pe_reset_and_recover() is used to recover EEH
error when the passthrou device are transferred to guest and
backwards. The content in the device's config space will be lost
on PE reset issued in the middle of the recovery. The function
saves/restores it before/after the reset. However, config access
to some adapters like Broadcom BCM5719 at this point will causes
fenced PHB. The config space is always blocked and we save 0xFF's
that are restored at late point. The memory BARs are totally
corrupted, causing another EEH error upon access to one of the
memory BARs.

This restores the config space on those adapters like BCM5719
from the content saved to the EEH device when it's populated,
to resolve above issue.

Fixes: 5cfb20b9 ("powerpc/eeh: Emulate EEH recovery for VFIO devices")
Signed-off-by: Gavin Shan <gwshan at linux.vnet.ibm.com>
Reviewed-by: Russell Currey <ruscur at russell.cc>
Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/powerpc/kernel/eeh_driver.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/arch/powerpc/kernel/eeh_driver.c b/arch/powerpc/kernel/eeh_driver.c
index e5f488c..16f315f 100644
--- a/arch/powerpc/kernel/eeh_driver.c
+++ b/arch/powerpc/kernel/eeh_driver.c
@@ -166,6 +166,16 @@ static void *eeh_dev_save_state(void *data, void *userdata)
 	if (!edev)
 		return NULL;

+	/*
+	 * We cannot access the config space on some adapters.
+	 * Otherwise, it will cause fenced PHB. We don't save
+	 * the content in their config space and will restore
+	 * from the initial config space saved when the EEH
+	 * device is created.
+	 */
+	if (edev->pe && (edev->pe->state & EEH_PE_CFG_RESTRICTED))
+		return NULL;
+
 	pdev = eeh_dev_to_pci_dev(edev);
 	if (!pdev)
 		return NULL;
@@ -305,6 +315,19 @@ static void *eeh_dev_restore_state(void *data, void *userdata)
 	if (!edev)
 		return NULL;

+	/*
+	 * The content in the config space isn't saved because
+	 * the blocked config space on some adapters. We have
+	 * to restore the initial saved config space when the
+	 * EEH device is created.
+	 */
+	if (edev->pe && (edev->pe->state & EEH_PE_CFG_RESTRICTED)) {
+		if (list_is_last(&edev->list, &edev->pe->edevs))
+			eeh_pe_restore_bars(edev->pe);
+
+		return NULL;
+	}
+
 	pdev = eeh_dev_to_pci_dev(edev);
 	if (!pdev)
 		return NULL;
--
2.7.4