Re: [PATCH v3 2/2] vdpasim: support doorbell mapping

From: Longpeng <redacted>

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 ).
---
 drivers/vdpa/vdpa_sim/vdpa_sim.c | 65 ++++++++++++++++++++++++++++++++
 drivers/vdpa/vdpa_sim/vdpa_sim.h |  3 ++
 2 files changed, 68 insertions(+)

diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
index b071f0d842fb..4fcfeb6e2fb8 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)
 {

@@ -246,6 +248,28 @@ 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)
 {

@@ -287,6 +311,13 @@ 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 = __get_free_page(GFP_KERNEL | __GFP_ZERO);
+       if (!vdpasim->notify)
+               goto err_iommu;

+
        vdpasim->config = kzalloc(dev_attr->config_size, GFP_KERNEL);
        if (!vdpasim->config)
                goto err_iommu;

@@ -498,16 +529,21 @@ static u8 vdpasim_get_status(struct vdpa_device *vdpa)
 static void vdpasim_set_status(struct vdpa_device *vdpa, u8 status)
 {
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
+       bool started = vdpasim->status & VIRTIO_CONFIG_S_DRIVER_OK;

        spin_lock(&vdpasim->lock);
        vdpasim->status = status;
        spin_unlock(&vdpasim->lock);
+       if (!started && (status & VIRTIO_CONFIG_S_DRIVER_OK))
+               schedule_delayed_work(&vdpasim->notify_work,
+                                     msecs_to_jiffies(VDPASIM_VRING_POLL_PERIOD));
 }

 static int vdpasim_reset(struct vdpa_device *vdpa)
 {
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);

+       cancel_delayed_work_sync(&vdpasim->notify_work);

        spin_lock(&vdpasim->lock);
        vdpasim->status = 0;
        vdpasim_do_reset(vdpasim);

@@ -672,11 +708,34 @@ 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++) {

@@ -693,6 +752,8 @@ static void vdpasim_free(struct vdpa_device *vdpa)
        vhost_iotlb_free(vdpasim->iommu);
        kfree(vdpasim->vqs);
        kfree(vdpasim->config);
+       if (vdpasim->notify)
+               free_page(vdpasim->notify);
 }

 static const struct vdpa_config_ops vdpasim_config_ops = {

@@ -704,6 +765,8 @@ 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,

@@ -737,6 +800,8 @@ 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..0769ccbd3911 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 */
+       unsigned long notify;
+       struct delayed_work notify_work;
 };

 struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *attr,
--

2.23.0