[PATCH] vdpasim: support doorbell mapping

["Longpeng(Mike)" <longpeng2@huawei.com>]

From: Longpeng <longpeng2@huawei.com>

Support doorbell mapping for vdpasim devices, then we can test the notify
passthrough feature even if there's no real hardware on hand.

Allocates a dummy page which used to emulate the notify page of the device.
All values written to this page would be ignored,  a periodic work will
check whether there're requests that need to process.

This cap is disabled as default, users can enable it as follow:
  modprobe vdpa_sim notify_passthrough=true

Signed-off-by: Longpeng <longpeng2@huawei.com>
---
 drivers/vdpa/vdpa_sim/vdpa_sim.c     | 71 ++++++++++++++++++++++++++--
 drivers/vdpa/vdpa_sim/vdpa_sim.h     |  5 +-
 drivers/vdpa/vdpa_sim/vdpa_sim_blk.c |  5 +-
 drivers/vdpa/vdpa_sim/vdpa_sim_net.c |  4 +-
 4 files changed, 76 insertions(+), 9 deletions(-)

diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
index 7438a89ce939..5c215b56b78b 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
@@ -14,6 +14,7 @@
 #include <linux/slab.h>
 #include <linux/sched.h>
 #include <linux/dma-map-ops.h>
+#include <asm/set_memory.h>
 #include <linux/vringh.h>
 #include <linux/vdpa.h>
 #include <linux/vhost_iotlb.h>
@@ -36,9 +37,15 @@ module_param(max_iotlb_entries, int, 0444);
 MODULE_PARM_DESC(max_iotlb_entries,
 		 "Maximum number of iotlb entries for each address space. 0 means unlimited. (default: 2048)");
 
+static bool notify_passthrough;
+module_param(notify_passthrough, bool, 0444);
+MODULE_PARM_DESC(notify_passthrough,
+		 "Enable vq notify(doorbell) area mapping. (default: false)");
+
 #define VDPASIM_QUEUE_ALIGN PAGE_SIZE
 #define VDPASIM_QUEUE_MAX 256
 #define VDPASIM_VENDOR_ID 0
+#define VDPASIM_VRING_POLL_PERIOD 100 /* ms */
 
 static struct vdpasim *vdpa_to_sim(struct vdpa_device *vdpa)
 {
@@ -276,7 +283,7 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
 	}
 
 	vdpasim->dev_attr = *dev_attr;
-	INIT_WORK(&vdpasim->work, dev_attr->work_fn);
+	INIT_DELAYED_WORK(&vdpasim->vring_work, dev_attr->work_fn);
 	spin_lock_init(&vdpasim->lock);
 	spin_lock_init(&vdpasim->iommu_lock);
 
@@ -287,6 +294,15 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
 	set_dma_ops(dev, &vdpasim_dma_ops);
 	vdpasim->vdpa.mdev = dev_attr->mgmt_dev;
 
+	if (notify_passthrough) {
+		vdpasim->notify = __get_free_page(GFP_KERNEL | __GFP_ZERO);
+		if (!vdpasim->notify)
+			goto err_iommu;
+#ifdef CONFIG_X86
+		set_memory_uc(vdpasim->notify, 1);
+#endif
+	}
+
 	vdpasim->config = kzalloc(dev_attr->config_size, GFP_KERNEL);
 	if (!vdpasim->config)
 		goto err_iommu;
@@ -357,8 +373,11 @@ static void vdpasim_kick_vq(struct vdpa_device *vdpa, u16 idx)
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 	struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
 
+	if (notify_passthrough)
+		return;
+
 	if (vq->ready)
-		schedule_work(&vdpasim->work);
+		schedule_work(&vdpasim->vring_work.work);
 }
 
 static void vdpasim_set_vq_cb(struct vdpa_device *vdpa, u16 idx,
@@ -495,6 +514,18 @@ static u8 vdpasim_get_status(struct vdpa_device *vdpa)
 	return status;
 }
 
+static void vdpasim_set_vring_work(struct vdpasim *vdpasim, bool start)
+{
+	if (!notify_passthrough)
+		return;
+
+	if (start)
+		schedule_delayed_work(&vdpasim->vring_work,
+				msecs_to_jiffies(VDPASIM_VRING_POLL_PERIOD));
+	else
+		cancel_delayed_work_sync(&vdpasim->vring_work);
+}
+
 static void vdpasim_set_status(struct vdpa_device *vdpa, u8 status)
 {
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
@@ -502,12 +533,16 @@ static void vdpasim_set_status(struct vdpa_device *vdpa, u8 status)
 	spin_lock(&vdpasim->lock);
 	vdpasim->status = status;
 	spin_unlock(&vdpasim->lock);
+
+	vdpasim_set_vring_work(vdpasim, status & VIRTIO_CONFIG_S_DRIVER_OK);
 }
 
 static int vdpasim_reset(struct vdpa_device *vdpa, bool clear)
 {
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 
+	vdpasim_set_vring_work(vdpasim, false);
+
 	spin_lock(&vdpasim->lock);
 	vdpasim->status = 0;
 	vdpasim_do_reset(vdpasim);
@@ -672,12 +707,24 @@ static int vdpasim_dma_unmap(struct vdpa_device *vdpa, unsigned int asid,
 	return 0;
 }
 
+static struct vdpa_notification_area
+vdpasim_get_vq_notification(struct vdpa_device *vdpa, u16 qid)
+{
+	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
+	struct vdpa_notification_area notify;
+
+	notify.addr = virt_to_phys((void *)vdpasim->notify);
+	notify.size = PAGE_SIZE;
+
+	return notify;
+}
+
 static void vdpasim_free(struct vdpa_device *vdpa)
 {
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 	int i;
 
-	cancel_work_sync(&vdpasim->work);
+	cancel_delayed_work_sync(&vdpasim->vring_work);
 
 	for (i = 0; i < vdpasim->dev_attr.nvqs; i++) {
 		vringh_kiov_cleanup(&vdpasim->vqs[i].out_iov);
@@ -693,7 +740,23 @@ static void vdpasim_free(struct vdpa_device *vdpa)
 	vhost_iotlb_free(vdpasim->iommu);
 	kfree(vdpasim->vqs);
 	kfree(vdpasim->config);
+	if (vdpasim->notify) {
+#ifdef CONFIG_X86
+		set_memory_wb(vdpasim->notify, 1);
+#endif
+		free_page(vdpasim->notify);
+	}
+}
+
+void vdpasim_schedule_work(struct vdpasim *vdpasim, bool sched_now)
+{
+	if (sched_now)
+		schedule_work(&vdpasim->vring_work.work);
+	else if (notify_passthrough)
+		schedule_delayed_work(&vdpasim->vring_work,
+				      msecs_to_jiffies(VDPASIM_VRING_POLL_PERIOD));
 }
+EXPORT_SYMBOL_GPL(vdpasim_schedule_work);
 
 static const struct vdpa_config_ops vdpasim_config_ops = {
 	.set_vq_address         = vdpasim_set_vq_address,
@@ -704,6 +767,7 @@ static const struct vdpa_config_ops vdpasim_config_ops = {
 	.get_vq_ready           = vdpasim_get_vq_ready,
 	.set_vq_state           = vdpasim_set_vq_state,
 	.get_vq_state           = vdpasim_get_vq_state,
+	.get_vq_notification    = vdpasim_get_vq_notification,
 	.get_vq_align           = vdpasim_get_vq_align,
 	.get_vq_group           = vdpasim_get_vq_group,
 	.get_device_features    = vdpasim_get_device_features,
@@ -737,6 +801,7 @@ static const struct vdpa_config_ops vdpasim_batch_config_ops = {
 	.get_vq_ready           = vdpasim_get_vq_ready,
 	.set_vq_state           = vdpasim_set_vq_state,
 	.get_vq_state           = vdpasim_get_vq_state,
+	.get_vq_notification    = vdpasim_get_vq_notification,
 	.get_vq_align           = vdpasim_get_vq_align,
 	.get_vq_group           = vdpasim_get_vq_group,
 	.get_device_features    = vdpasim_get_device_features,
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.h b/drivers/vdpa/vdpa_sim/vdpa_sim.h
index 0e78737dcc16..da0866834918 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.h
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.h
@@ -53,7 +53,7 @@ struct vdpasim_dev_attr {
 struct vdpasim {
 	struct vdpa_device vdpa;
 	struct vdpasim_virtqueue *vqs;
-	struct work_struct work;
+	struct delayed_work vring_work;
 	struct vdpasim_dev_attr dev_attr;
 	/* spinlock to synchronize virtqueue state */
 	spinlock_t lock;
@@ -69,10 +69,13 @@ struct vdpasim {
 	bool running;
 	/* spinlock to synchronize iommu table */
 	spinlock_t iommu_lock;
+	/* dummy notify page */
+	unsigned long notify;
 };
 
 struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *attr,
 			       const struct vdpa_dev_set_config *config);
+void vdpasim_schedule_work(struct vdpasim *vdpasim, bool sched_now);
 
 /* TODO: cross-endian support */
 static inline bool vdpasim_is_little_endian(struct vdpasim *vdpasim)
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
index c6db1a1baf76..8a640ea82284 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
@@ -288,7 +288,7 @@ static bool vdpasim_blk_handle_req(struct vdpasim *vdpasim,
 
 static void vdpasim_blk_work(struct work_struct *work)
 {
-	struct vdpasim *vdpasim = container_of(work, struct vdpasim, work);
+	struct vdpasim *vdpasim = container_of(work, struct vdpasim, vring_work.work);
 	bool reschedule = false;
 	int i;
 
@@ -325,8 +325,7 @@ static void vdpasim_blk_work(struct work_struct *work)
 out:
 	spin_unlock(&vdpasim->lock);
 
-	if (reschedule)
-		schedule_work(&vdpasim->work);
+	vdpasim_schedule_work(vdpasim, reschedule);
 }
 
 static void vdpasim_blk_get_config(struct vdpasim *vdpasim, void *config)
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_net.c b/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
index c3cb225ea469..8b998952384b 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
@@ -145,7 +145,7 @@ static void vdpasim_handle_cvq(struct vdpasim *vdpasim)
 
 static void vdpasim_net_work(struct work_struct *work)
 {
-	struct vdpasim *vdpasim = container_of(work, struct vdpasim, work);
+	struct vdpasim *vdpasim = container_of(work, struct vdpasim, vring_work.work);
 	struct vdpasim_virtqueue *txq = &vdpasim->vqs[1];
 	struct vdpasim_virtqueue *rxq = &vdpasim->vqs[0];
 	ssize_t read, write;
@@ -196,7 +196,7 @@ static void vdpasim_net_work(struct work_struct *work)
 		vdpasim_net_complete(rxq, write);
 
 		if (++pkts > 4) {
-			schedule_work(&vdpasim->work);
+			vdpasim_schedule_work(vdpasim, true);
 			goto out;
 		}
 	}
-- 
2.23.0