diff --git a/Documentation/ABI/stable/sysfs-driver-dma-idxd b/Documentation/ABI/stable/sysfs-driver-dma-idxd
index df4afbccf0379ffeaf763318f7081272d8060c8d..4d3a23eb05b923dc52b84df625cc0f70c428fe44 100644
--- a/Documentation/ABI/stable/sysfs-driver-dma-idxd
+++ b/Documentation/ABI/stable/sysfs-driver-dma-idxd
@@ -220,6 +220,13 @@ Contact: dmaengine@vger.kernel.org
Description: Show the current number of entries in this WQ if WQ Occupancy
Support bit WQ capabilities is 1.
+What: /sys/bus/dsa/devices/wq<m>.<n>/enqcmds_retries
+Date Oct 29, 2021
+KernelVersion: 5.17.0
+Contact: dmaengine@vger.kernel.org
+Description: Indicate the number of retires for an enqcmds submission on a shared wq.
+ A max value to set attribute is capped at 64.
+
What: /sys/bus/dsa/devices/engine<m>.<n>/group_id
Date: Oct 25, 2019
KernelVersion: 5.6.0
diff --git a/drivers/dma/idxd/device.c b/drivers/dma/idxd/device.c
index 36e213a8108dd4c1bf0ab769c0ecc45d83c7a2b8..5a50ee6f6881f03878227b039533ee0f7bd016d6 100644
--- a/drivers/dma/idxd/device.c
+++ b/drivers/dma/idxd/device.c
@@ -387,6 +387,7 @@ static void idxd_wq_disable_cleanup(struct idxd_wq *wq)
wq->threshold = 0;
wq->priority = 0;
wq->ats_dis = 0;
+ wq->enqcmds_retries = IDXD_ENQCMDS_RETRIES;
clear_bit(WQ_FLAG_DEDICATED, &wq->flags);
clear_bit(WQ_FLAG_BLOCK_ON_FAULT, &wq->flags);
memset(wq->name, 0, WQ_NAME_SIZE);
diff --git a/drivers/dma/idxd/idxd.h b/drivers/dma/idxd/idxd.h
index 89e98d69115ba2e273cd3e17d8f790ca17235abf..6b9bfdc557fe78ac4072272bf9755ec46f60e5b2 100644
--- a/drivers/dma/idxd/idxd.h
+++ b/drivers/dma/idxd/idxd.h
@@ -52,6 +52,9 @@ enum idxd_type {
#define IDXD_NAME_SIZE 128
#define IDXD_PMU_EVENT_MAX 64
+#define IDXD_ENQCMDS_RETRIES 32
+#define IDXD_ENQCMDS_MAX_RETRIES 64
+
struct idxd_device_driver {
const char *name;
enum idxd_dev_type *type;
@@ -173,6 +176,7 @@ struct idxd_dma_chan {
struct idxd_wq {
void __iomem *portal;
u32 portal_offset;
+ unsigned int enqcmds_retries;
struct percpu_ref wq_active;
struct completion wq_dead;
struct completion wq_resurrect;
@@ -584,6 +588,7 @@ int idxd_wq_init_percpu_ref(struct idxd_wq *wq);
int idxd_submit_desc(struct idxd_wq *wq, struct idxd_desc *desc);
struct idxd_desc *idxd_alloc_desc(struct idxd_wq *wq, enum idxd_op_type optype);
void idxd_free_desc(struct idxd_wq *wq, struct idxd_desc *desc);
+int idxd_enqcmds(struct idxd_wq *wq, void __iomem *portal, const void *desc);
/* dmaengine */
int idxd_register_dma_device(struct idxd_device *idxd);
diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
index 94ecd4bf0f0ed0cf5597db2ad3d9b25f0f52725f..8b3afce9ea67a9c005941756b1159a8cf9b8c147 100644
--- a/drivers/dma/idxd/init.c
+++ b/drivers/dma/idxd/init.c
@@ -248,6 +248,7 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
init_completion(&wq->wq_resurrect);
wq->max_xfer_bytes = WQ_DEFAULT_MAX_XFER;
wq->max_batch_size = WQ_DEFAULT_MAX_BATCH;
+ wq->enqcmds_retries = IDXD_ENQCMDS_RETRIES;
wq->wqcfg = kzalloc_node(idxd->wqcfg_size, GFP_KERNEL, dev_to_node(dev));
if (!wq->wqcfg) {
put_device(conf_dev);
diff --git a/drivers/dma/idxd/irq.c b/drivers/dma/idxd/irq.c
index a3bf3ea84587aef32486e9f049408fb25e4102ac..0b0055a0ad2a15bff16638474aade9076ab3f28b 100644
--- a/drivers/dma/idxd/irq.c
+++ b/drivers/dma/idxd/irq.c
@@ -98,7 +98,7 @@ static void idxd_int_handle_revoke_drain(struct idxd_irq_entry *ie)
if (wq_dedicated(wq)) {
iosubmit_cmds512(portal, &desc, 1);
} else {
- rc = enqcmds(portal, &desc);
+ rc = idxd_enqcmds(wq, portal, &desc);
/* This should not fail unless hardware failed. */
if (rc < 0)
dev_warn(dev, "Failed to submit drain desc on wq %d\n", wq->id);
diff --git a/drivers/dma/idxd/submit.c b/drivers/dma/idxd/submit.c
index 776fa81db61d8abefb6bc40412facc291095ffc8..569815a84e95bd2ceb451e8e399090970787d615 100644
--- a/drivers/dma/idxd/submit.c
+++ b/drivers/dma/idxd/submit.c
@@ -123,6 +123,29 @@ static void llist_abort_desc(struct idxd_wq *wq, struct idxd_irq_entry *ie,
idxd_dma_complete_txd(found, IDXD_COMPLETE_ABORT, false);
}
+/*
+ * ENQCMDS typically fail when the WQ is inactive or busy. On host submission, the driver
+ * has better control of number of descriptors being submitted to a shared wq by limiting
+ * the number of driver allocated descriptors to the wq size. However, when the swq is
+ * exported to a guest kernel, it may be shared with multiple guest kernels. This means
+ * the likelihood of getting busy returned on the swq when submitting goes significantly up.
+ * Having a tunable retry mechanism allows the driver to keep trying for a bit before giving
+ * up. The sysfs knob can be tuned by the system administrator.
+ */
+int idxd_enqcmds(struct idxd_wq *wq, void __iomem *portal, const void *desc)
+{
+ int rc, retries = 0;
+
+ do {
+ rc = enqcmds(portal, desc);
+ if (rc == 0)
+ break;
+ cpu_relax();
+ } while (retries++ < wq->enqcmds_retries);
+
+ return rc;
+}
+
int idxd_submit_desc(struct idxd_wq *wq, struct idxd_desc *desc)
{
struct idxd_device *idxd = wq->idxd;
@@ -166,13 +189,7 @@ int idxd_submit_desc(struct idxd_wq *wq, struct idxd_desc *desc)
if (wq_dedicated(wq)) {
iosubmit_cmds512(portal, desc->hw, 1);
} else {
- /*
- * It's not likely that we would receive queue full rejection
- * since the descriptor allocation gates at wq size. If we
- * receive a -EAGAIN, that means something went wrong such as the
- * device is not accepting descriptor at all.
- */
- rc = enqcmds(portal, desc->hw);
+ rc = idxd_enqcmds(wq, portal, desc->hw);
if (rc < 0) {
percpu_ref_put(&wq->wq_active);
/* abort operation frees the descriptor */
diff --git a/drivers/dma/idxd/sysfs.c b/drivers/dma/idxd/sysfs.c
index 90857e77627361a1272668a0587cdca95ff40ecd..c0fec88ff6c1f88cc4f9faca8d26e115f03e08cf 100644
--- a/drivers/dma/idxd/sysfs.c
+++ b/drivers/dma/idxd/sysfs.c
@@ -945,6 +945,41 @@ static ssize_t wq_occupancy_show(struct device *dev, struct device_attribute *at
static struct device_attribute dev_attr_wq_occupancy =
__ATTR(occupancy, 0444, wq_occupancy_show, NULL);
+static ssize_t wq_enqcmds_retries_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct idxd_wq *wq = confdev_to_wq(dev);
+
+ if (wq_dedicated(wq))
+ return -EOPNOTSUPP;
+
+ return sysfs_emit(buf, "%u\n", wq->enqcmds_retries);
+}
+
+static ssize_t wq_enqcmds_retries_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct idxd_wq *wq = confdev_to_wq(dev);
+ int rc;
+ unsigned int retries;
+
+ if (wq_dedicated(wq))
+ return -EOPNOTSUPP;
+
+ rc = kstrtouint(buf, 10, &retries);
+ if (rc < 0)
+ return rc;
+
+ if (retries > IDXD_ENQCMDS_MAX_RETRIES)
+ retries = IDXD_ENQCMDS_MAX_RETRIES;
+
+ wq->enqcmds_retries = retries;
+ return count;
+}
+
+static struct device_attribute dev_attr_wq_enqcmds_retries =
+ __ATTR(enqcmds_retries, 0644, wq_enqcmds_retries_show, wq_enqcmds_retries_store);
+
static struct attribute *idxd_wq_attributes[] = {
&dev_attr_wq_clients.attr,
&dev_attr_wq_state.attr,
@@ -961,6 +996,7 @@ static struct attribute *idxd_wq_attributes[] = {
&dev_attr_wq_max_batch_size.attr,
&dev_attr_wq_ats_disable.attr,
&dev_attr_wq_occupancy.attr,
+ &dev_attr_wq_enqcmds_retries.attr,
NULL,
};