[SRU][F][PATCH 1/1] s390/pci: fix enabling a reserved PCI function

[frank.heimes at canonical.com]

From: Niklas Schnelle <schnelle at linux.ibm.com>

BugLink: https://bugs.launchpad.net/bugs/1891437

In usual IPL or hot plug scenarios a zPCI function transitions directly
from reserved (invisible to Linux) to configured state or is configured
by Linux itself using an SCLP, however it can also first go from
reserved to standby and then from standby to configured without
Linux initiative.
In this scenario we first get a PEC event 0x302 and then 0x301.  This may
happen for example when the device is deconfigured at another LPAR and
made available for this LPAR. It may also happen under z/VM when
a device is attached while in some inconsistent state.

However when we get the 0x301 the device is already known to zPCI
so calling zpci_create() will add it twice resulting in the below
BUG. Instead we should only enable the existing device and finally
scan it through the PCI subsystem.

list_add double add: new=00000000ed5a9008, prev=00000000ed5a9008, next=0000000083502300.
kernel BUG at lib/list_debug.c:31!
Krnl PSW : 0704c00180000000 0000000082dc2db8 (__list_add_valid+0x70/0xa8)
Call Trace:
 [<0000000082dc2db8>] __list_add_valid+0x70/0xa8
([<0000000082dc2db4>] __list_add_valid+0x6c/0xa8)
 [<00000000828ea920>] zpci_create_device+0x60/0x1b0
 [<00000000828ef04a>] zpci_event_availability+0x282/0x2f0
 [<000000008315f848>] chsc_process_crw+0x2b8/0xa18
 [<000000008316735c>] crw_collect_info+0x254/0x348
 [<00000000829226ea>] kthread+0x14a/0x168
 [<000000008319d5c0>] ret_from_fork+0x24/0x2c

Fixes: f606b3ef47c9 ("s390/pci: adapt events for zbus")
Reported-by: Alexander Egorenkov <egorenar at linux.ibm.com>
Tested-by: Alexander Egorenkov <egorenar at linux.ibm.com>
Signed-off-by: Niklas Schnelle <schnelle at linux.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens at de.ibm.com>
(cherry picked from commit 3047766bc6ec9c6bc9ece85b45a41ff401e8d988)
Signed-off-by: Frank Heimes <frank.heimes at canonical.com>
---
 arch/s390/pci/pci_event.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/s390/pci/pci_event.c b/arch/s390/pci/pci_event.c
index 08e1d619398e..fdebd286f402 100644
--- a/arch/s390/pci/pci_event.c
+++ b/arch/s390/pci/pci_event.c
@@ -94,7 +94,18 @@ static void __zpci_event_availability(struct zpci_ccdf_avail *ccdf)
 		}
 		zdev->fh = ccdf->fh;
 		zdev->state = ZPCI_FN_STATE_CONFIGURED;
-		zpci_create_device(zdev);
+		ret = zpci_enable_device(zdev);
+		if (ret)
+			break;
+
+		pdev = pci_scan_single_device(zdev->zbus->bus, zdev->devfn);
+		if (!pdev)
+			break;
+
+		pci_bus_add_device(pdev);
+		pci_lock_rescan_remove();
+		pci_bus_add_devices(zdev->zbus->bus);
+		pci_unlock_rescan_remove();
 		break;
 	case 0x0302: /* Reserved -> Standby */
 		if (!zdev) {
-- 
2.25.1