[PATCH v4 2/2] 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 is used to emulate the notify page of the device,
all VQs share the same notify register  that initiated to 0xffff. A  periodic
work will check whether there're requests need to process ( the value of the
notify register is 0xffff or not ).

We can test on QEMU with:
 -device vhost-vdpa-device-pci,vhostdev=/dev/vhost-vdpa-0,page-per-vq=on

Signed-off-by: Longpeng <longpeng2@huawei.com>
---
 drivers/vdpa/vdpa_sim/vdpa_sim.c | 67 ++++++++++++++++++++++++++++++++
 drivers/vdpa/vdpa_sim/vdpa_sim.h |  3 ++
 2 files changed, 70 insertions(+)

diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
index cb88891b44a8..5a8c820b179f 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
@@ -39,6 +39,8 @@ MODULE_PARM_DESC(max_iotlb_entries,
 #define VDPASIM_QUEUE_ALIGN PAGE_SIZE
 #define VDPASIM_QUEUE_MAX 256
 #define VDPASIM_VENDOR_ID 0
+#define VDPASIM_VRING_POLL_PERIOD 100 /* ms */
+#define VDPASIM_NOTIFY_DEFVAL 0xffff
 
 static struct vdpasim *vdpa_to_sim(struct vdpa_device *vdpa)
 {
@@ -245,6 +247,28 @@ static const struct dma_map_ops vdpasim_dma_ops = {
 static const struct vdpa_config_ops vdpasim_config_ops;
 static const struct vdpa_config_ops vdpasim_batch_config_ops;
 
+static void vdpasim_notify_work(struct work_struct *work)
+{
+	struct vdpasim *vdpasim;
+	u16 *val;
+
+	vdpasim = container_of(work, struct vdpasim, notify_work.work);
+
+	if (!(vdpasim->status & VIRTIO_CONFIG_S_DRIVER_OK))
+		goto out;
+
+	if (!vdpasim->running)
+		goto out;
+
+	val = (u16 *)vdpasim->notify;
+	if (xchg(val, VDPASIM_NOTIFY_DEFVAL) != VDPASIM_NOTIFY_DEFVAL)
+		schedule_work(&vdpasim->work);
+
+out:
+	schedule_delayed_work(&vdpasim->notify_work,
+			      msecs_to_jiffies(VDPASIM_VRING_POLL_PERIOD));
+}
+
 struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
 			       const struct vdpa_dev_set_config *config)
 {
@@ -286,6 +310,13 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
 	set_dma_ops(dev, &vdpasim_dma_ops);
 	vdpasim->vdpa.mdev = dev_attr->mgmt_dev;
 
+	INIT_DELAYED_WORK(&vdpasim->notify_work, vdpasim_notify_work);
+
+	vdpasim->notify = (u16 *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
+	if (!vdpasim->notify)
+		goto err_iommu;
+	WRITE_ONCE(*vdpasim->notify, VDPASIM_NOTIFY_DEFVAL);
+
 	vdpasim->config = kzalloc(dev_attr->config_size, GFP_KERNEL);
 	if (!vdpasim->config)
 		goto err_iommu;
@@ -320,6 +351,13 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
 
 	vdpasim->vdpa.dma_dev = dev;
 
+	/*
+ 	 * Start periodic (every 100ms) notify work, it won't introduce
+ 	 * any overhead if the device is not started.
+	 */
+	schedule_delayed_work(&vdpasim->notify_work,
+			      msecs_to_jiffies(VDPASIM_VRING_POLL_PERIOD));
+
 	return vdpasim;
 
 err_iommu:
@@ -671,11 +709,34 @@ static int vdpasim_dma_unmap(struct vdpa_device *vdpa, unsigned int asid,
 	return 0;
 }
 
+static pgprot_t vdpasim_get_vq_notification_pgprot(struct vdpa_device *vdpa,
+						   u16 qid, pgprot_t prot)
+{
+	/*
+	 * We use normal RAM pages to emulate the vq notification area, so
+	 * just keep the pgprot as it mmaped.
+	 */
+	return prot;
+}
+
+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_delayed_work_sync(&vdpasim->notify_work);
 	cancel_work_sync(&vdpasim->work);
 
 	for (i = 0; i < vdpasim->dev_attr.nvqs; i++) {
@@ -694,6 +755,8 @@ static void vdpasim_free(struct vdpa_device *vdpa)
 	kfree(vdpasim->iommu);
 	kfree(vdpasim->vqs);
 	kfree(vdpasim->config);
+	if (vdpasim->notify)
+		free_page((unsigned long)vdpasim->notify);
 }
 
 static const struct vdpa_config_ops vdpasim_config_ops = {
@@ -705,6 +768,8 @@ 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_notification_pgprot = vdpasim_get_vq_notification_pgprot,
 	.get_vq_align           = vdpasim_get_vq_align,
 	.get_vq_group           = vdpasim_get_vq_group,
 	.get_device_features    = vdpasim_get_device_features,
@@ -738,6 +803,8 @@ 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_notification_pgprot = vdpasim_get_vq_notification_pgprot,
 	.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..786e902de0b2 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.h
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.h
@@ -69,6 +69,9 @@ struct vdpasim {
 	bool running;
 	/* spinlock to synchronize iommu table */
 	spinlock_t iommu_lock;
+	/* dummy notify page */
+	u16 *notify;
+	struct delayed_work notify_work;
 };
 
 struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *attr,
-- 
2.23.0