Re: [PATCH v7 2/2] PCI: rpaphp: Error out on busy status from get-sensor-state
From: Bjorn Helgaas <helgaas@kernel.org>
Date: 2023-08-01 21:38:17
Also in:
linux-pci, lkml
On Mon, Jul 24, 2023 at 02:25:19PM +0530, Mahesh Salgaonkar wrote:
When certain PHB HW failure causes pHyp to recover PHB, it marks the PE state as temporarily unavailable until recovery is complete. This also triggers an EEH handler in Linux which needs to notify drivers, and perform recovery. But before notifying the driver about the PCI error it uses get_adapter_state()->get-sensor-state() operation of the hotplug_slot to determine if the slot contains a device or not. if the slot is empty, the recovery is skipped entirely.
It's helpful to use the exact function name so it's greppable; I think get_adapter_status() or rpaphp_get_sensor_state()? s/if the slot is empty,/If the slot is empty,/
However on certain PHB failures, the RTAS call get-sensor-state() returns extended busy error (9902) until PHB is recovered by pHyp. Once PHB is recovered, the get-sensor-state() returns success with correct presence status. The RTAS call interface rtas_get_sensor() loops over the RTAS call on extended delay return code (9902) until the return value is either success (0) or error (-1). This causes the EEH handler to get stuck for ~6 seconds before it could notify that the PCI error has been detected and stop any active operations. Hence with running I/O traffic, during this 6 seconds, the network driver continues its operation and hits a timeout (netdev watchdog). ------------ [52732.244731] DEBUG: ibm_read_slot_reset_state2() [52732.244762] DEBUG: ret = 0, rets[0]=5, rets[1]=1, rets[2]=4000, rets[3]=> [52732.244798] DEBUG: in eeh_slot_presence_check [52732.244804] DEBUG: error state check [52732.244807] DEBUG: Is slot hotpluggable [52732.244810] DEBUG: hotpluggable ops ? [52732.244953] DEBUG: Calling ops->get_adapter_status [52732.244958] DEBUG: calling rpaphp_get_sensor_state [52736.564262] ------------[ cut here ]------------ [52736.564299] NETDEV WATCHDOG: enP64p1s0f3 (tg3): transmit queue 0 timed o> [52736.564324] WARNING: CPU: 1442 PID: 0 at net/sched/sch_generic.c:478 dev> [...] [52736.564505] NIP [c000000000c32368] dev_watchdog+0x438/0x440 [52736.564513] LR [c000000000c32364] dev_watchdog+0x434/0x440 ------------ On timeouts, network driver starts dumping debug information to console (e.g bnx2 driver calls bnx2x_panic_dump()), and go into recovery path while pHyp is still recovering the PHB. As part of recovery, the driver tries to reset the device and it keeps failing since every PCI read/write returns ff's. And when EEH recovery kicks-in, the driver is unable to recover the device. This impacts the ssh connection and leads to the system being inaccessible. To get the NIC working again it needs a reboot or re-assign the I/O adapter from HMC. [ 9531.168587] EEH: Beginning: 'slot_reset' [ 9531.168601] PCI 0013:01:00.0#10000: EEH: Invoking bnx2x->slot_reset() [...] [ 9614.110094] bnx2x: [bnx2x_func_stop:9129(enP19p1s0f0)]FUNC_STOP ramrod failed. Running a dry transaction [ 9614.110300] bnx2x: [bnx2x_igu_int_disable:902(enP19p1s0f0)]BUG! Proper val not read from IGU! [ 9629.178067] bnx2x: [bnx2x_fw_command:3055(enP19p1s0f0)]FW failed to respond! [ 9629.178085] bnx2x 0013:01:00.0 enP19p1s0f0: bc 7.10.4 [ 9629.178091] bnx2x: [bnx2x_fw_dump_lvl:789(enP19p1s0f0)]Cannot dump MCP info while in PCI error [ 9644.241813] bnx2x: [bnx2x_io_slot_reset:14245(enP19p1s0f0)]IO slot reset --> driver unload [...] [ 9644.241819] PCI 0013:01:00.0#10000: EEH: bnx2x driver reports: 'disconnect' [ 9644.241823] PCI 0013:01:00.1#10000: EEH: Invoking bnx2x->slot_reset() [ 9644.241827] bnx2x: [bnx2x_io_slot_reset:14229(enP19p1s0f1)]IO slot reset initializing... [ 9644.241916] bnx2x 0013:01:00.1: enabling device (0140 -> 0142) [ 9644.258604] bnx2x: [bnx2x_io_slot_reset:14245(enP19p1s0f1)]IO slot reset --> driver unload [ 9644.258612] PCI 0013:01:00.1#10000: EEH: bnx2x driver reports: 'disconnect' [ 9644.258615] EEH: Finished:'slot_reset' with aggregate recovery state:'disconnect' [ 9644.258620] EEH: Unable to recover from failure from PHB#13-PE#10000. [ 9644.261811] EEH: Beginning: 'error_detected(permanent failure)' [...] [ 9644.261823] EEH: Finished:'error_detected(permanent failure)' Hence, it becomes important to inform driver about the PCI error detection as early as possible, so that driver is aware of PCI error and waits for EEH handler's next action for successful recovery.
I don't really understand the connection between EEH and get_adapter_status(), but I guess this probably refers to arch/powerpc/kernel/eeh_driver.c, not the PCI core aer.c and err.c?
Current implementation uses rtas_get_sensor() API which blocks the slot check state until RTAS call returns success. To avoid this, fix the PCI hotplug driver (rpaphp) to return an error (-EBUSY) if the slot presence state can not be detected immediately while PE is in EEH recovery state. Change rpaphp_get_sensor_state() to invoke rtas_call(get-sensor-state) directly only if the respective PE is in EEH recovery state, and take actions based on RTAS return status. This way EEH handler will not be blocked on rpaphp_get_sensor_state() and can immediately notify driver about the PCI error and stop any active operations. In normal cases (non-EEH case) rpaphp_get_sensor_state() will continue to invoke rtas_get_sensor() as it was earlier with no change in existing behavior. Signed-off-by: Mahesh Salgaonkar <mahesh@linux.ibm.com> Reviewed-by: Nathan Lynch <redacted>
Seems like maybe both patches could go via a ppc tree since they seem very ppc-specific? A couple minor comments below. Acked-by: Bjorn Helgaas <bhelgaas@google.com>
+ * get_adapter_status() can be called by the EEH handler during EEH recovery. + * On certain PHB failures, the RTAS call get-seHsor-state() returns extended
Looks like a typo in "get-seHsor-state"?
+static int __rpaphp_get_sensor_state(struct slot *slot, int *state)
+{
+#ifdef CONFIG_EEH
Is this #ifdef redundant? It looks like this file is only compiled
if CONFIG_EEH is set:
config HOTPLUG_PCI_RPA
tristate "RPA PCI Hotplug driver"
depends on PPC_PSERIES && EEH
obj-$(CONFIG_HOTPLUG_PCI_RPA) += rpaphp.o
rpaphp-objs := rpaphp_core.o \
rpaphp_pci.o \
rpaphp_slot.o
quoted hunk ↗ jump to hunk
+ int rc; + int token = rtas_token("get-sensor-state"); + struct pci_dn *pdn; + struct eeh_pe *pe; + struct pci_controller *phb = PCI_DN(slot->dn)->phb; + + if (token == RTAS_UNKNOWN_SERVICE) + return -ENOENT; + + /* + * Fallback to existing method for empty slot or PE isn't in EEH + * recovery. + */ + pdn = list_first_entry_or_null(&PCI_DN(phb->dn)->child_list, + struct pci_dn, list); + if (!pdn) + goto fallback; + + pe = eeh_dev_to_pe(pdn->edev); + if (pe && (pe->state & EEH_PE_RECOVERING)) { + rc = rtas_call(token, 2, 2, state, DR_ENTITY_SENSE, + slot->index); + return rtas_get_sensor_errno(rc); + } +fallback: +#endif + return rtas_get_sensor(DR_ENTITY_SENSE, slot->index, state); +} + int rpaphp_get_sensor_state(struct slot *slot, int *state) { int rc; int setlevel; - rc = rtas_get_sensor(DR_ENTITY_SENSE, slot->index, state); + rc = __rpaphp_get_sensor_state(slot, state); if (rc < 0) { if (rc == -EFAULT || rc == -EEXIST) {@@ -40,8 +117,7 @@ int rpaphp_get_sensor_state(struct slot *slot, int *state) dbg("%s: power on slot[%s] failed rc=%d.\n", __func__, slot->name, rc); } else { - rc = rtas_get_sensor(DR_ENTITY_SENSE, - slot->index, state); + rc = __rpaphp_get_sensor_state(slot, state); } } else if (rc == -ENODEV) info("%s: slot is unusable\n", __func__);