[PATCH 1/3] PCI/AER: Fix NULL pci_ops return when hotplug a pci bus which was doing aer error inject

[Yijing Wang <wangyijing@huawei.com>]

When we inject aer errors to the target pci device by aer_inject module, the pci_ops of pci
bus which the target device is on will be assign to pci_ops_aer.So if the target pci device
is a bridge, once we hotplug the pci bus(child bus) which the target device bridges to, child
bus's pci_ops will be assigned to pci_ops_aer too.Now every access to the child bus's device
will result to system panic, because it return NULL pci_ops in pci_read_aer.

CallTrace:
bash[5908]: NaT consumption 17179869216 [1]
Modules linked in: aer_inject cpufreq_conservative cpufreq_userspace cpufreq_pow
ersave acpi_cpufreq binfmt_misc fuse nls_iso8859_1 loop ipmi_si(+) ipmi_devintf
ipmi_msghandler dm_mod ppdev iTCO_wdt iTCO_vendor_support sg igb parport_pc i2c_
i801 mptctl i2c_core serio_raw hid_generic lpc_ich mfd_core parport button conta
iner usbhid hid uhci_hcd ehci_hcd usbcore usb_common sd_mod crc_t10dif ext3 mbca
che jbd fan processor ide_pci_generic ide_core ata_piix libata mptsas mptscsih m
ptbase scsi_transport_sas scsi_mod thermal thermal_sys hwmon

Pid: 5908, CPU 9, comm:                 bash
psr : 00001010085a2010 ifs : 800000000000048e ip  : [<a000000220b815b0>]    Not
tainted (3.5.0-rc6yijing-repo)
ip is at pci_read_aer+0x330/0x460 [aer_inject]
unat: 0000000000000000 pfs : 000000000000048e rsc : 0000000000000003
rnat: 0000000000000000 bsps: 0000000000000000 pr  : 65519aa6a6969aa5
ldrs: 0000000000000000 ccv : ffffffff00000001 fpsr: 0009804c8a70033f
csd : 0000000000000000 ssd : 0000000000000000
b0  : a000000220b815b0 b6  : a000000220b81280 b7  : a0000001006d56a0
f6  : 1003e0000000000000005 f7  : 1003e0000000000000028
f8  : 1003e00000000000000c8 f9  : 1003e0000000000000005
f10 : 1003e627ec1e2f4c0d8a7 f11 : 1003e0000000000000011
r1  : a0000001014e63c0 r2  : 0000000000000738 r3  : 000000000000fffe
r8  : 0000000000000736 r9  : 0000000000000042 r10 : e000001f08f4c898
r11 : 0000000000000000 r12 : e000000f3dfcfdc0 r13 : e000000f3dfc0000
r14 : 0000000000000738 r15 : 0000000000004000 r16 : a000000220b827c8
r17 : a000000220b827b8 r18 : ffffffffffffff00 r19 : e000000f073b0110
r20 : 0000000000000042 r21 : e000000f073b0114 r22 : 0000000000000000
r23 : e000000f073b0118 r24 : a0000001009e0e49 r25 : 0000000000000001
r26 : 0000000000007041 r27 : e000000f3dfcfde0 r28 : 0000000000000000
r29 : e000000f3dfcfc08 r30 : a000000220b827c8 r31 : e000001f074d6000

Call Trace:
 [<a000000100016500>] show_stack+0x80/0xa0
                                sp=e000000f3dfcf800 bsp=e000000f3dfc1758
 [<a000000100016b60>] show_regs+0x640/0x920
                                sp=e000000f3dfcf9d0 bsp=e000000f3dfc1700
 [<a000000100040770>] die+0x190/0x2c0
                                sp=e000000f3dfcf9e0 bsp=e000000f3dfc16c0
 [<a0000001000408f0>] die_if_kernel+0x50/0x80
                                sp=e000000f3dfcf9e0 bsp=e000000f3dfc1690
 [<a000000100903a90>] ia64_fault+0xf0/0x15e0
                                sp=e000000f3dfcf9e0 bsp=e000000f3dfc1640
 [<a00000010000c0a0>] ia64_native_leave_kernel+0x0/0x270
                                sp=e000000f3dfcfbf0 bsp=e000000f3dfc1640
 [<a000000220b815b0>] pci_read_aer+0x330/0x460 [aer_inject]
                                sp=e000000f3dfcfdc0 bsp=e000000f3dfc15c8
 [<a0000001004ace00>] pci_bus_read_config_dword+0xe0/0x140
                                sp=e000000f3dfcfdc0 bsp=e000000f3dfc1580
 [<a0000001004b0c10>] pci_bus_read_dev_vendor_id+0x50/0x200
                                sp=e000000f3dfcfdd0 bsp=e000000f3dfc1530
 [<a0000001008d3d10>] pci_scan_single_device+0x90/0x200
                                sp=e000000f3dfcfdd0 bsp=e000000f3dfc14f8
 [<a0000001004b24b0>] pci_scan_slot+0xb0/0x320
                                sp=e000000f3dfcfde0 bsp=e000000f3dfc14a8
 [<a0000001008d9e90>] pci_scan_child_bus+0x90/0x2e0
                                sp=e000000f3dfcfde0 bsp=e000000f3dfc1468
 [<a0000001008d9580>] pci_scan_bridge+0x540/0xdc0
                                sp=e000000f3dfcfde0 bsp=e000000f3dfc13d0
 [<a0000001008da0b0>] pci_scan_child_bus+0x2b0/0x2e0
                                sp=e000000f3dfcfe00 bsp=e000000f3dfc1390
 [<a0000001008d5bd0>] pci_rescan_bus+0x50/0x220
                                sp=e000000f3dfcfe00 bsp=e000000f3dfc1358
 [<a0000001004c2ab0>] bus_rescan_store+0xf0/0x160
                                sp=e000000f3dfcfe10 bsp=e000000f3dfc1328
 [<a0000001006110b0>] bus_attr_store+0x70/0xa0
                                sp=e000000f3dfcfe20 bsp=e000000f3dfc12f0
 [<a000000100343b00>] sysfs_write_file+0x240/0x340
                                sp=e000000f3dfcfe20 bsp=e000000f3dfc1298
 [<a00000010025e230>] vfs_write+0x1b0/0x3a0
                                sp=e000000f3dfcfe20 bsp=e000000f3dfc1250
 [<a00000010025e5e0>] sys_write+0x80/0x100
                                sp=e000000f3dfcfe20 bsp=e000000f3dfc11d0
 [<a00000010000bf20>] ia64_ret_from_syscall+0x0/0x20
                                sp=e000000f3dfcfe30 bsp=e000000f3dfc11d0
 [<a000000000040720>] __kernel_syscall_via_break+0x0/0x20
                                sp=e000000f3dfd0000 bsp=e000000f3dfc11d0
Disabling lock debugging due to kernel taint

Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Jiang Liu <liuj97@gmail.com>
---
 drivers/pci/pcie/aer/aer_inject.c |   21 +++++++++++++++++++++
 1 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/drivers/pci/pcie/aer/aer_inject.c b/drivers/pci/pcie/aer/aer_inject.c
index 5222986..fc28785 100644
--- a/drivers/pci/pcie/aer/aer_inject.c
+++ b/drivers/pci/pcie/aer/aer_inject.c
@@ -109,6 +109,19 @@ static struct aer_error *__find_aer_error_by_dev(struct pci_dev *dev)
 	return __find_aer_error((u16)domain, dev->bus->number, dev->devfn);
 }
 
+static bool pci_is_upstream_bus(struct pci_bus *bus, struct pci_bus *up_bus)
+{
+	struct pci_bus *pbus = bus->parent;
+
+	while (pbus) {
+		if (pbus == up_bus)
+			return true;
+		pbus = pbus->parent;
+	}
+
+	return false;
+}
+
 /* inject_lock must be held before calling */
 static struct pci_ops *__find_pci_bus_ops(struct pci_bus *bus)
 {
@@ -118,6 +131,13 @@ static struct pci_ops *__find_pci_bus_ops(struct pci_bus *bus)
 		if (bus_ops->bus == bus)
 			return bus_ops->ops;
 	}
+
+	/* here can't find bus_ops, fall back to get bus_ops of upstream bus */
+	list_for_each_entry(bus_ops, &pci_bus_ops_list, list) {
+		if (pci_is_upstream_bus(bus, bus_ops->bus))
+			return bus_ops->ops;
+	}
+
 	return NULL;
 }
 
@@ -506,6 +526,7 @@ static struct miscdevice aer_inject_device = {
 	.fops = &aer_inject_fops,
 };
 
+
 static int __init aer_inject_init(void)
 {
 	return misc_register(&aer_inject_device);
-- 
1.7.1