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Message-ID: <20230213070446-mutt-send-email-mst@kernel.org>
Date: Mon, 13 Feb 2023 07:05:21 -0500
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Jason Wang <jasowang@...hat.com>
Cc: "Longpeng(Mike)" <longpeng2@...wei.com>, stefanha@...hat.com,
sgarzare@...hat.com, arei.gonglei@...wei.com, yechuan@...wei.com,
huangzhichao@...wei.com, virtualization@...ts.linux-foundation.org,
linux-kernel@...r.kernel.org, eperezma@...hat.com
Subject: Re: [PATCH v3 2/2] vdpasim: support doorbell mapping
On Sun, Jan 29, 2023 at 02:19:51PM +0800, Jason Wang wrote:
> On Sun, Jan 29, 2023 at 10:51 AM Longpeng(Mike) <longpeng2@...wei.com> wrote:
> >
> > From: Longpeng <longpeng2@...wei.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 ).
> > ---
> > 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;
>
> We can simply avoid the advertising notification area in this case.
>
> > + *(u16 *)vdpasim->notify = VDPASIM_NOTIFY_DEFVAL;
>
> WRITE_ONCE()?
it is just initialization so it should not matter.
> > +
> > 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;
>
> Do we need to do the check under the vdpasim->lock?
>
> >
> > 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);
>
> Do we need to do this after setting running to zero? Otherwise it's racy.
>
> Thanks
>
> > 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
> >
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