[PATCH 4.4 066/137] powerpc/eeh: Fix stale cached primary bus

Greg Kroah-Hartman
2016-02-24T04:20:45Z

From: Gavin Shan <gwshan@linux.vnet.ibm.com>

commit 05ba75f848647135f063199dc0e9f40fee769724 upstream.

When PE is created, its primary bus is cached to pe->bus. At later
point, the cached primary bus is returned from eeh_pe_bus_get().
However, we could get stale cached primary bus and run into kernel
crash in one case: full hotplug as part of fenced PHB error recovery
releases all PCI busses under the PHB at unplugging time and recreate
them at plugging time. pe->bus is still dereferencing the PCI bus
that was released.

This adds another PE flag (EEH_PE_PRI_BUS) to represent the validity
of pe->bus. pe->bus is updated when its first child EEH device is
online and the flag is set. Before unplugging in full hotplug for
error recovery, the flag is cleared.

Fixes: 8cdb2833 ("powerpc/eeh: Trace PCI bus from PE")
Reported-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Reported-by: Pradipta Ghosh <pradghos@in.ibm.com>
Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Tested-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/powerpc/include/asm/eeh.h | 1 +
arch/powerpc/kernel/eeh_driver.c | 3 +++
arch/powerpc/kernel/eeh_pe.c | 2 +-
arch/powerpc/platforms/powernv/eeh-powernv.c | 5 ++++-
4 files changed, 9 insertions(+), 2 deletions(-)

--- a/arch/powerpc/include/asm/eeh.h
+++ b/arch/powerpc/include/asm/eeh.h
@@ -81,6 +81,7 @@ struct pci_dn;
#define EEH_PE_KEEP (1 << 8) /* Keep PE on hotplug */
#define EEH_PE_CFG_RESTRICTED (1 << 9) /* Block config on error */
#define EEH_PE_REMOVED (1 << 10) /* Removed permanently */
+#define EEH_PE_PRI_BUS (1 << 11) /* Cached primary bus */

struct eeh_pe {
int type; /* PE type: PHB/Bus/Device */
--- a/arch/powerpc/kernel/eeh_driver.c
+++ b/arch/powerpc/kernel/eeh_driver.c
@@ -564,6 +564,7 @@ static int eeh_reset_device(struct eeh_p
*/
eeh_pe_state_mark(pe, EEH_PE_KEEP);
if (bus) {
+ eeh_pe_state_clear(pe, EEH_PE_PRI_BUS);
pci_lock_rescan_remove();
pcibios_remove_pci_devices(bus);
pci_unlock_rescan_remove();
@@ -803,6 +804,7 @@ perm_error:
* the their PCI config any more.
*/
if (frozen_bus) {
+ eeh_pe_state_clear(pe, EEH_PE_PRI_BUS);
eeh_pe_dev_mode_mark(pe, EEH_DEV_REMOVED);

pci_lock_rescan_remove();
@@ -886,6 +888,7 @@ static void eeh_handle_special_event(voi
continue;

/* Notify all devices to be down */
+ eeh_pe_state_clear(pe, EEH_PE_PRI_BUS);
bus = eeh_pe_bus_get(phb_pe);
eeh_pe_dev_traverse(pe,
eeh_report_failure, NULL);
--- a/arch/powerpc/kernel/eeh_pe.c
+++ b/arch/powerpc/kernel/eeh_pe.c
@@ -928,7 +928,7 @@ struct pci_bus *eeh_pe_bus_get(struct ee
bus = pe->phb->bus;
} else if (pe->type & EEH_PE_BUS ||
pe->type & EEH_PE_DEVICE) {
- if (pe->bus) {
+ if (pe->state & EEH_PE_PRI_BUS) {
bus = pe->bus;
goto out;
}
--- a/arch/powerpc/platforms/powernv/eeh-powernv.c
+++ b/arch/powerpc/platforms/powernv/eeh-powernv.c
@@ -444,9 +444,12 @@ static void *pnv_eeh_probe(struct pci_dn
* PCI devices of the PE are expected to be removed prior
* to PE reset.
*/
- if (!edev->pe->bus)
+ if (!(edev->pe->state & EEH_PE_PRI_BUS)) {
edev->pe->bus = pci_find_bus(hose->global_number,
pdn->busno);
+ if (edev->pe->bus)
+ edev->pe->state |= EEH_PE_PRI_BUS;
+ }

/*
* Enable EEH explicitly so that we will do EEH check