cxlflash: Base error recovery support

Introduce support for enhanced I/O error handling.

A device state is added to track 3 possible states of the device:

Normal - the device is operating normally and is fully operational

Limbo - the device is in a reset/recovery scenario and its operational
        status is paused

Failed/terminating - the device has either failed to be reset/recovered
                     or is being terminated (removed); it is no longer
                     operational

All operations are allowed when the device is operating normally. When the
device transitions to limbo state, I/O must be paused. To help accomplish
this, a wait queue is introduced where existing and new threads can wait
until the device is no longer in limbo. When coming out of limbo, threads
need to check the state and error out gracefully when encountering the
failed state. When the device transitions to the failed/terminating state,
normal operations are no longer allowed. Only specially designated
operations related to graceful cleanup are permitted.

Signed-off-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Signed-off-by: Manoj N. Kumar <manoj@linux.vnet.ibm.com>
Reviewed-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Michael Neuling <mikey@neuling.org>
Reviewed-by: Wen Xiong <wenxiong@linux.vnet.ibm.com>
Reviewed-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <JBottomley@Odin.com>

drivers/scsi/cxlflash/Kconfig

@@ -4,7 +4,7 @@
 
 config CXLFLASH
 	tristate "Support for IBM CAPI Flash"
-	depends on PCI && SCSI && CXL
+	depends on PCI && SCSI && CXL && EEH
 	default m
 	help
 	  Allows CAPI Accelerated IO to Flash

drivers/scsi/cxlflash/common.h

@@ -76,6 +76,12 @@ enum cxlflash_init_state {
 	INIT_STATE_SCSI
 };
 
+enum cxlflash_state {
+	STATE_NORMAL,	/* Normal running state, everything good */
+	STATE_LIMBO,	/* Limbo running state, trying to reset/recover */
+	STATE_FAILTERM	/* Failed/terminating state, error out users/threads */
+};
+
 /*
  * Each context has its own set of resource handles that is visible
  * only from that context.
@@ -91,8 +97,6 @@ struct cxlflash_cfg {
 
 	ulong cxlflash_regs_pci;
 
-	wait_queue_head_t eeh_waitq;
-
 	struct work_struct work_q;
 	enum cxlflash_init_state init_state;
 	enum cxlflash_lr_state lr_state;
@@ -105,7 +109,8 @@ struct cxlflash_cfg {
 
 	wait_queue_head_t tmf_waitq;
 	bool tmf_active;
-	u8 err_recovery_active:1;
+	wait_queue_head_t limbo_waitq;
+	enum cxlflash_state state;
 };
 
 struct afu_cmd {

drivers/scsi/cxlflash/main.c

@@ -353,6 +353,7 @@ static int cxlflash_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scp)
 	struct cxlflash_cfg *cfg = (struct cxlflash_cfg *)host->hostdata;
 	struct afu *afu = cfg->afu;
 	struct pci_dev *pdev = cfg->dev;
+	struct device *dev = &cfg->dev->dev;
 	struct afu_cmd *cmd;
 	u32 port_sel = scp->device->channel + 1;
 	int nseg, i, ncount;
@@ -380,6 +381,21 @@ static int cxlflash_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scp)
 	}
 	spin_unlock_irqrestore(&cfg->tmf_waitq.lock, lock_flags);
 
+	switch (cfg->state) {
+	case STATE_LIMBO:
+		dev_dbg_ratelimited(dev, "%s: device in limbo!\n", __func__);
+		rc = SCSI_MLQUEUE_HOST_BUSY;
+		goto out;
+	case STATE_FAILTERM:
+		dev_dbg_ratelimited(dev, "%s: device has failed!\n", __func__);
+		scp->result = (DID_NO_CONNECT << 16);
+		scp->scsi_done(scp);
+		rc = 0;
+		goto out;
+	default:
+		break;
+	}
+
 	cmd = cxlflash_cmd_checkout(afu);
 	if (unlikely(!cmd)) {
 		pr_err("%s: could not get a free command\n", __func__);
@@ -455,9 +471,21 @@ static int cxlflash_eh_device_reset_handler(struct scsi_cmnd *scp)
 		 get_unaligned_be32(&((u32 *)scp->cmnd)[2]),
 		 get_unaligned_be32(&((u32 *)scp->cmnd)[3]));
 
-	rcr = send_tmf(afu, scp, TMF_LUN_RESET);
-	if (unlikely(rcr))
+	switch (cfg->state) {
+	case STATE_NORMAL:
+		rcr = send_tmf(afu, scp, TMF_LUN_RESET);
+		if (unlikely(rcr))
+			rc = FAILED;
+		break;
+	case STATE_LIMBO:
+		wait_event(cfg->limbo_waitq, cfg->state != STATE_LIMBO);
+		if (cfg->state == STATE_NORMAL)
+			break;
+		/* fall through */
+	default:
 		rc = FAILED;
+		break;
+	}
 
 	pr_debug("%s: returning rc=%d\n", __func__, rc);
 	return rc;
@@ -487,11 +515,29 @@ static int cxlflash_eh_host_reset_handler(struct scsi_cmnd *scp)
 		 get_unaligned_be32(&((u32 *)scp->cmnd)[2]),
 		 get_unaligned_be32(&((u32 *)scp->cmnd)[3]));
 
-	rcr = cxlflash_afu_reset(cfg);
-	if (rcr == 0)
-		rc = SUCCESS;
-	else
+	switch (cfg->state) {
+	case STATE_NORMAL:
+		cfg->state = STATE_LIMBO;
+		scsi_block_requests(cfg->host);
+
+		rcr = cxlflash_afu_reset(cfg);
+		if (rcr) {
+			rc = FAILED;
+			cfg->state = STATE_FAILTERM;
+		} else
+			cfg->state = STATE_NORMAL;
+		wake_up_all(&cfg->limbo_waitq);
+		scsi_unblock_requests(cfg->host);
+		break;
+	case STATE_LIMBO:
+		wait_event(cfg->limbo_waitq, cfg->state != STATE_LIMBO);
+		if (cfg->state == STATE_NORMAL)
+			break;
+		/* fall through */
+	default:
 		rc = FAILED;
+		break;
+	}
 
 	pr_debug("%s: returning rc=%d\n", __func__, rc);
 	return rc;
@@ -642,7 +688,7 @@ static void cxlflash_wait_for_pci_err_recovery(struct cxlflash_cfg *cfg)
 	struct pci_dev *pdev = cfg->dev;
 
 	if (pci_channel_offline(pdev))
-		wait_event_timeout(cfg->eeh_waitq,
+		wait_event_timeout(cfg->limbo_waitq,
 				   !pci_channel_offline(pdev),
 				   CXLFLASH_PCI_ERROR_RECOVERY_TIMEOUT);
 }
@@ -825,6 +871,8 @@ static void cxlflash_remove(struct pci_dev *pdev)
 						    !cfg->tmf_active);
 	spin_unlock_irqrestore(&cfg->tmf_waitq.lock, lock_flags);
 
+	cfg->state = STATE_FAILTERM;
+
 	switch (cfg->init_state) {
 	case INIT_STATE_SCSI:
 		scsi_remove_host(cfg->host);
@@ -1879,6 +1927,8 @@ static int init_afu(struct cxlflash_cfg *cfg)
 	struct afu *afu = cfg->afu;
 	struct device *dev = &cfg->dev->dev;
 
+	cxl_perst_reloads_same_image(cfg->cxl_afu, true);
+
 	rc = init_mc(cfg);
 	if (rc) {
 		dev_err(dev, "%s: call to init_mc failed, rc=%d!\n",
@@ -2021,6 +2071,12 @@ void cxlflash_wait_resp(struct afu *afu, struct afu_cmd *cmd)
  * the sync. This design point requires calling threads to not be on interrupt
  * context due to the possibility of sleeping during concurrent sync operations.
  *
+ * AFU sync operations are only necessary and allowed when the device is
+ * operating normally. When not operating normally, sync requests can occur as
+ * part of cleaning up resources associated with an adapter prior to removal.
+ * In this scenario, these requests are simply ignored (safe due to the AFU
+ * going away).
+ *
  * Return:
  *	0 on success
  *	-1 on failure
@@ -2028,11 +2084,17 @@ void cxlflash_wait_resp(struct afu *afu, struct afu_cmd *cmd)
 int cxlflash_afu_sync(struct afu *afu, ctx_hndl_t ctx_hndl_u,
 		      res_hndl_t res_hndl_u, u8 mode)
 {
+	struct cxlflash_cfg *cfg = afu->parent;
 	struct afu_cmd *cmd = NULL;
 	int rc = 0;
 	int retry_cnt = 0;
 	static DEFINE_MUTEX(sync_active);
 
+	if (cfg->state != STATE_NORMAL) {
+		pr_debug("%s: Sync not required! (%u)\n", __func__, cfg->state);
+		return 0;
+	}
+
 	mutex_lock(&sync_active);
 retry:
 	cmd = cxlflash_cmd_checkout(afu);
@@ -2116,12 +2178,17 @@ int cxlflash_afu_reset(struct cxlflash_cfg *cfg)
  */
 static void cxlflash_worker_thread(struct work_struct *work)
 {
-	struct cxlflash_cfg *cfg =
-	    container_of(work, struct cxlflash_cfg, work_q);
+	struct cxlflash_cfg *cfg = container_of(work, struct cxlflash_cfg,
+						work_q);
 	struct afu *afu = cfg->afu;
 	int port;
 	ulong lock_flags;
 
+	/* Avoid MMIO if the device has failed */
+
+	if (cfg->state != STATE_NORMAL)
+		return;
+
 	spin_lock_irqsave(cfg->host->host_lock, lock_flags);
 
 	if (cfg->lr_state == LINK_RESET_REQUIRED) {
@@ -2200,10 +2267,9 @@ static int cxlflash_probe(struct pci_dev *pdev,
 	cfg->dev = pdev;
 	cfg->dev_id = (struct pci_device_id *)dev_id;
 	cfg->mcctx = NULL;
-	cfg->err_recovery_active = 0;
 
 	init_waitqueue_head(&cfg->tmf_waitq);
-	init_waitqueue_head(&cfg->eeh_waitq);
+	init_waitqueue_head(&cfg->limbo_waitq);
 
 	INIT_WORK(&cfg->work_q, cxlflash_worker_thread);
 	cfg->lr_state = LINK_RESET_INVALID;
@@ -2259,6 +2325,91 @@ out_remove:
 	goto out;
 }
 
+/**
+ * cxlflash_pci_error_detected() - called when a PCI error is detected
+ * @pdev:	PCI device struct.
+ * @state:	PCI channel state.
+ *
+ * Return: PCI_ERS_RESULT_NEED_RESET or PCI_ERS_RESULT_DISCONNECT
+ */
+static pci_ers_result_t cxlflash_pci_error_detected(struct pci_dev *pdev,
+						    pci_channel_state_t state)
+{
+	struct cxlflash_cfg *cfg = pci_get_drvdata(pdev);
+	struct device *dev = &cfg->dev->dev;
+
+	dev_dbg(dev, "%s: pdev=%p state=%u\n", __func__, pdev, state);
+
+	switch (state) {
+	case pci_channel_io_frozen:
+		cfg->state = STATE_LIMBO;
+
+		/* Turn off legacy I/O */
+		scsi_block_requests(cfg->host);
+
+		term_mc(cfg, UNDO_START);
+		stop_afu(cfg);
+
+		return PCI_ERS_RESULT_NEED_RESET;
+	case pci_channel_io_perm_failure:
+		cfg->state = STATE_FAILTERM;
+		wake_up_all(&cfg->limbo_waitq);
+		scsi_unblock_requests(cfg->host);
+		return PCI_ERS_RESULT_DISCONNECT;
+	default:
+		break;
+	}
+	return PCI_ERS_RESULT_NEED_RESET;
+}
+
+/**
+ * cxlflash_pci_slot_reset() - called when PCI slot has been reset
+ * @pdev:	PCI device struct.
+ *
+ * This routine is called by the pci error recovery code after the PCI
+ * slot has been reset, just before we should resume normal operations.
+ *
+ * Return: PCI_ERS_RESULT_RECOVERED or PCI_ERS_RESULT_DISCONNECT
+ */
+static pci_ers_result_t cxlflash_pci_slot_reset(struct pci_dev *pdev)
+{
+	int rc = 0;
+	struct cxlflash_cfg *cfg = pci_get_drvdata(pdev);
+	struct device *dev = &cfg->dev->dev;
+
+	dev_dbg(dev, "%s: pdev=%p\n", __func__, pdev);
+
+	rc = init_afu(cfg);
+	if (unlikely(rc)) {
+		dev_err(dev, "%s: EEH recovery failed! (%d)\n", __func__, rc);
+		return PCI_ERS_RESULT_DISCONNECT;
+	}
+
+	return PCI_ERS_RESULT_RECOVERED;
+}
+
+/**
+ * cxlflash_pci_resume() - called when normal operation can resume
+ * @pdev:	PCI device struct
+ */
+static void cxlflash_pci_resume(struct pci_dev *pdev)
+{
+	struct cxlflash_cfg *cfg = pci_get_drvdata(pdev);
+	struct device *dev = &cfg->dev->dev;
+
+	dev_dbg(dev, "%s: pdev=%p\n", __func__, pdev);
+
+	cfg->state = STATE_NORMAL;
+	wake_up_all(&cfg->limbo_waitq);
+	scsi_unblock_requests(cfg->host);
+}
+
+static const struct pci_error_handlers cxlflash_err_handler = {
+	.error_detected = cxlflash_pci_error_detected,
+	.slot_reset = cxlflash_pci_slot_reset,
+	.resume = cxlflash_pci_resume,
+};
+
 /*
  * PCI device structure
  */
@@ -2267,6 +2418,7 @@ static struct pci_driver cxlflash_driver = {
 	.id_table = cxlflash_pci_table,
 	.probe = cxlflash_probe,
 	.remove = cxlflash_remove,
+	.err_handler = &cxlflash_err_handler,
 };
 
 /**

drivers/scsi/cxlflash/main.h

@@ -22,7 +22,7 @@
 
 #define CXLFLASH_NAME		"cxlflash"
 #define CXLFLASH_ADAPTER_NAME	"IBM POWER CXL Flash Adapter"
-#define CXLFLASH_DRIVER_DATE	"(June 2, 2015)"
+#define CXLFLASH_DRIVER_DATE	"(August 13, 2015)"
 
 #define PCI_DEVICE_ID_IBM_CORSA	0x04F0
 #define CXLFLASH_SUBS_DEV_ID	0x04F0
@@ -101,4 +101,8 @@ struct asyc_intr_info {
 #define LINK_RESET	0x02
 };
 
+#ifndef CONFIG_CXL_EEH
+#define cxl_perst_reloads_same_image(_a, _b) do { } while (0)
+#endif
+
 #endif /* _CXLFLASH_MAIN_H */