Patch "powerpc/eeh: Fix fenced PHB caused by eeh_slot_error_detail()" has been added to the 4.1-stable tree

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

powerpc/eeh: Fix fenced PHB caused by eeh_slot_error_detail()

to the 4.1-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-fix-fenced-phb-caused-by-eeh_slot_error_detail.patch
and it can be found in the queue-4.1 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, 28 Aug 2015 11:57:00 +1000
Subject: powerpc/eeh: Fix fenced PHB caused by eeh_slot_error_detail()

From: Gavin Shan <[email protected]>

commit 259800135c654a098d9f0adfdd3d1f20eef1f231 upstream.

The config space of some PCI devices can't be accessed when their PEs are in frozen state. Otherwise, fenced PHB might be seen. Those PEs are identified with flag EEH_PE_CFG_RESTRICTED, meaing EEH_PE_CFG_BLOCKED is set automatically when the PE is put to frozen state (EEH_PE_ISOLATED). eeh_slot_error_detail() restores PCI device BARs with eeh_pe_restore_bars(), which then calls eeh_ops->restore_config() to reinitialize the PCI device in (OPAL) firmware. eeh_ops->restore_config() produces PCI config access that causes fenced PHB. The problem was reported on below adapter:

0001:01:00.0 0200: 14e4:168e (rev 10)
0001:01:00.0 Ethernet controller: Broadcom Corporation \
NetXtreme II BCM57810 10 Gigabit Ethernet (rev 10)

This fixes the issue by skipping eeh_pe_restore_bars() in eeh_slot_error_detail() when EEH_PE_CFG_BLOCKED is set for the PE.

---
 arch/powerpc/kernel/eeh.c |   21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

@@ -310,11 +310,26 @@ void eeh_slot_error_detail(struct eeh_pe
 	if (!(pe->type & EEH_PE_PHB)) {
 		if (eeh_has_flag(EEH_ENABLE_IO_FOR_LOG))
 			eeh_pci_enable(pe, EEH_OPT_THAW_MMIO);
+
+		/*
+		 * The config space of some PCI devices can't be accessed
+		 * when their PEs are in frozen state. Otherwise, fenced
+		 * PHB might be seen. Those PEs are identified with flag
+		 * EEH_PE_CFG_RESTRICTED, indicating EEH_PE_CFG_BLOCKED
+		 * is set automatically when the PE is put to EEH_PE_ISOLATED.
+		 *
+		 * Restoring BARs possibly triggers PCI config access in
+		 * (OPAL) firmware and then causes fenced PHB. If the
+		 * PCI config is blocked with flag EEH_PE_CFG_BLOCKED, it's
+		 * pointless to restore BARs and dump config space.
+		 */
 		eeh_ops->configure_bridge(pe);
-		eeh_pe_restore_bars(pe);
+		if (!(pe->state & EEH_PE_CFG_BLOCKED)) {
+			eeh_pe_restore_bars(pe);
 
-		pci_regs_buf[0] = 0;
-		eeh_pe_traverse(pe, eeh_dump_pe_log, &loglen);
+			pci_regs_buf[0] = 0;
+			eeh_pe_traverse(pe, eeh_dump_pe_log, &loglen);
+		}
 	}
 
 	eeh_ops->get_log(pe, severity, pci_regs_buf, loglen);

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

queue-4.1/powerpc-eeh-probe-after-unbalanced-kref-check.patch queue-4.1/powerpc-eeh-fix-fenced-phb-caused-by-eeh_slot_error_detail.patch queue-4.1/powerpc-pseries-fix-corrupted-pdn-list.patch