NTB: Xeon Errata Workaround

There is a Xeon hardware errata related to writes to SDOORBELL or
B2BDOORBELL in conjunction with inbound access to NTB MMIO Space, which
may hang the system.  To workaround this issue, use one of the memory
windows to access the interrupt and scratch pad registers on the remote
system.  This bypasses the issue, but removes one of the memory windows
from use by the transport.  This reduction of MWs necessitates adding
some logic to determine the number of available MWs.

Since some NTB usage methodologies may have unidirectional traffic, the
ability to disable the workaround via modparm has been added.

See BF113 in
http://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/xeon-c5500-c3500-spec-update.pdf
See BT119 in
http://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/xeon-e5-family-spec-update.pdf

Signed-off-by: Jon Mason <jon.mason@intel.com>

1 files changed, 49 insertions, 29 deletions

diff --git a/drivers/ntb/ntb_transport.c b/drivers/ntb/ntb_transport.c
index c3089151aa49..f7380e959656 100644
--- a/drivers/ntb/ntb_transport.c
+++ b/drivers/ntb/ntb_transport.c
@@ -64,7 +64,7 @@ static unsigned int transport_mtu = 0x401E;
 module_param(transport_mtu, uint, 0644);
 MODULE_PARM_DESC(transport_mtu, "Maximum size of NTB transport packets");
 
-static unsigned char max_num_clients = 2;
+static unsigned char max_num_clients;
 module_param(max_num_clients, byte, 0644);
 MODULE_PARM_DESC(max_num_clients, "Maximum number of NTB transport clients");
 
@@ -150,7 +150,7 @@ struct ntb_transport {
 	struct list_head client_devs;
 
 	struct ntb_device *ndev;
-	struct ntb_transport_mw mw[NTB_NUM_MW];
+	struct ntb_transport_mw *mw;
 	struct ntb_transport_qp *qps;
 	unsigned int max_qps;
 	unsigned long qp_bitmap;
@@ -182,7 +182,7 @@ enum {
 	MAX_SPAD,
 };
 
-#define QP_TO_MW(qp)		((qp) % NTB_NUM_MW)
+#define QP_TO_MW(ndev, qp)	((qp) % ntb_max_mw(ndev))
 #define NTB_QP_DEF_NUM_ENTRIES	100
 #define NTB_LINK_DOWN_TIMEOUT	10
 
@@ -474,19 +474,22 @@ static void ntb_transport_setup_qp_mw(struct ntb_transport *nt,
 {
 	struct ntb_transport_qp *qp = &nt->qps[qp_num];
 	unsigned int rx_size, num_qps_mw;
-	u8 mw_num = QP_TO_MW(qp_num);
+	u8 mw_num, mw_max;
 	unsigned int i;
 
+	mw_max = ntb_max_mw(nt->ndev);
+	mw_num = QP_TO_MW(nt->ndev, qp_num);
+
 	WARN_ON(nt->mw[mw_num].virt_addr == NULL);
 
-	if (nt->max_qps % NTB_NUM_MW && mw_num < nt->max_qps % NTB_NUM_MW)
-		num_qps_mw = nt->max_qps / NTB_NUM_MW + 1;
+	if (nt->max_qps % mw_max && mw_num < nt->max_qps % mw_max)
+		num_qps_mw = nt->max_qps / mw_max + 1;
 	else
-		num_qps_mw = nt->max_qps / NTB_NUM_MW;
+		num_qps_mw = nt->max_qps / mw_max;
 
 	rx_size = (unsigned int) nt->mw[mw_num].size / num_qps_mw;
 	qp->remote_rx_info = nt->mw[mw_num].virt_addr +
-			     (qp_num / NTB_NUM_MW * rx_size);
+			     (qp_num / mw_max * rx_size);
 	rx_size -= sizeof(struct ntb_rx_info);
 
 	qp->rx_buff = qp->remote_rx_info + 1;
@@ -630,7 +633,7 @@ static void ntb_transport_link_work(struct work_struct *work)
 	int rc, i;
 
 	/* send the local info, in the opposite order of the way we read it */
-	for (i = 0; i < NTB_NUM_MW; i++) {
+	for (i = 0; i < ntb_max_mw(ndev); i++) {
 		rc = ntb_write_remote_spad(ndev, MW0_SZ_HIGH + (i * 2),
 					   ntb_get_mw_size(ndev, i) >> 32);
 		if (rc) {
@@ -650,10 +653,10 @@ static void ntb_transport_link_work(struct work_struct *work)
 		}
 	}
 
-	rc = ntb_write_remote_spad(ndev, NUM_MWS, NTB_NUM_MW);
+	rc = ntb_write_remote_spad(ndev, NUM_MWS, ntb_max_mw(ndev));
 	if (rc) {
 		dev_err(&pdev->dev, "Error writing %x to remote spad %d\n",
-			NTB_NUM_MW, NUM_MWS);
+			ntb_max_mw(ndev), NUM_MWS);
 		goto out;
 	}
 
@@ -698,11 +701,11 @@ static void ntb_transport_link_work(struct work_struct *work)
 		goto out;
 	}
 
-	if (val != NTB_NUM_MW)
+	if (val != ntb_max_mw(ndev))
 		goto out;
 	dev_dbg(&pdev->dev, "Remote number of mws = %d\n", val);
 
-	for (i = 0; i < NTB_NUM_MW; i++) {
+	for (i = 0; i < ntb_max_mw(ndev); i++) {
 		u64 val64;
 
 		rc = ntb_read_remote_spad(ndev, MW0_SZ_HIGH + (i * 2), &val);
@@ -744,7 +747,7 @@ static void ntb_transport_link_work(struct work_struct *work)
 	return;
 
 out1:
-	for (i = 0; i < NTB_NUM_MW; i++)
+	for (i = 0; i < ntb_max_mw(ndev); i++)
 		ntb_free_mw(nt, i);
 out:
 	if (ntb_hw_link_status(ndev))
@@ -798,7 +801,10 @@ static void ntb_transport_init_queue(struct ntb_transport *nt,
 {
 	struct ntb_transport_qp *qp;
 	unsigned int num_qps_mw, tx_size;
-	u8 mw_num = QP_TO_MW(qp_num);
+	u8 mw_num, mw_max;
+
+	mw_max = ntb_max_mw(nt->ndev);
+	mw_num = QP_TO_MW(nt->ndev, qp_num);
 
 	qp = &nt->qps[qp_num];
 	qp->qp_num = qp_num;
@@ -808,14 +814,14 @@ static void ntb_transport_init_queue(struct ntb_transport *nt,
 	qp->client_ready = NTB_LINK_DOWN;
 	qp->event_handler = NULL;
 
-	if (nt->max_qps % NTB_NUM_MW && mw_num < nt->max_qps % NTB_NUM_MW)
-		num_qps_mw = nt->max_qps / NTB_NUM_MW + 1;
+	if (nt->max_qps % mw_max && mw_num < nt->max_qps % mw_max)
+		num_qps_mw = nt->max_qps / mw_max + 1;
 	else
-		num_qps_mw = nt->max_qps / NTB_NUM_MW;
+		num_qps_mw = nt->max_qps / mw_max;
 
 	tx_size = (unsigned int) ntb_get_mw_size(qp->ndev, mw_num) / num_qps_mw;
 	qp->rx_info = ntb_get_mw_vbase(nt->ndev, mw_num) +
-		      (qp_num / NTB_NUM_MW * tx_size);
+		      (qp_num / mw_max * tx_size);
 	tx_size -= sizeof(struct ntb_rx_info);
 
 	qp->tx_mw = qp->rx_info + 1;
@@ -862,13 +868,23 @@ int ntb_transport_init(struct pci_dev *pdev)
 		goto err;
 	}
 
-	nt->max_qps = min(nt->ndev->max_cbs, max_num_clients);
+	nt->mw = kcalloc(ntb_max_mw(nt->ndev), sizeof(struct ntb_transport_mw),
+			 GFP_KERNEL);
+	if (!nt->mw) {
+		rc = -ENOMEM;
+		goto err1;
+	}
+
+	if (max_num_clients)
+		nt->max_qps = min(ntb_max_cbs(nt->ndev), max_num_clients);
+	else
+		nt->max_qps = min(ntb_max_cbs(nt->ndev), ntb_max_mw(nt->ndev));
 
 	nt->qps = kcalloc(nt->max_qps, sizeof(struct ntb_transport_qp),
 			  GFP_KERNEL);
 	if (!nt->qps) {
 		rc = -ENOMEM;
-		goto err1;
+		goto err2;
 	}
 
 	nt->qp_bitmap = ((u64) 1 << nt->max_qps) - 1;
@@ -882,22 +898,24 @@ int ntb_transport_init(struct pci_dev *pdev)
 	rc = ntb_register_event_callback(nt->ndev,
 					 ntb_transport_event_callback);
 	if (rc)
-		goto err2;
+		goto err3;
 
 	INIT_LIST_HEAD(&nt->client_devs);
 	rc = ntb_bus_init(nt);
 	if (rc)
-		goto err3;
+		goto err4;
 
 	if (ntb_hw_link_status(nt->ndev))
 		schedule_delayed_work(&nt->link_work, 0);
 
 	return 0;
 
-err3:
+err4:
 	ntb_unregister_event_callback(nt->ndev);
-err2:
+err3:
 	kfree(nt->qps);
+err2:
+	kfree(nt->mw);
 err1:
 	ntb_unregister_transport(nt->ndev);
 err:
@@ -908,6 +926,7 @@ err:
 void ntb_transport_free(void *transport)
 {
 	struct ntb_transport *nt = transport;
+	struct ntb_device *ndev = nt->ndev;
 	struct pci_dev *pdev;
 	int i;
 
@@ -924,15 +943,16 @@ void ntb_transport_free(void *transport)
 
 	cancel_delayed_work_sync(&nt->link_work);
 
-	ntb_unregister_event_callback(nt->ndev);
+	ntb_unregister_event_callback(ndev);
 
-	pdev = ntb_query_pdev(nt->ndev);
+	pdev = ntb_query_pdev(ndev);
 
-	for (i = 0; i < NTB_NUM_MW; i++)
+	for (i = 0; i < ntb_max_mw(ndev); i++)
 		ntb_free_mw(nt, i);
 
 	kfree(nt->qps);
-	ntb_unregister_transport(nt->ndev);
+	kfree(nt->mw);
+	ntb_unregister_transport(ndev);
 	kfree(nt);
 }