[PATCH] vdpasim: support doorbell mapping

Michael S. Tsirkin
Mon, 28 Nov 2022 10:19:11 -0000

On Mon, Nov 28, 2022 at 04:19:30PM +0800, Longpeng (Mike, Cloud Infrastructure
Service Product Dept.) wrote:
>
>
> ? 2022/11/28 12:05, Jason Wang ??:
> > On Mon, Nov 28, 2022 at 10:56 AM Longpeng(Mike) <longpeng2 at
huawei.com> wrote:
> > >
> > > From: Longpeng <longpeng2 at 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.
> >
> > You can use vp_vdpa in L1 plus page_ver_vq in L0 to test it in L2.
> > That is how I test it.
> >
> Yes, using nested virtualization can work, but it's hard to deploy in
my
> working environment for some reasons, so I decided to emulate this
> capability in vdpasim, it's much easier.
>
> > >
> > > 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 seems tricky, it means the device is working even if there's
no
>
> Right. It just try to make the vdpasim device work properly, but the
vdpasim
> device is only used for testing, so maybe the tricky emulation is
> acceptable?

Maybe. You can try enabling VIRTIO_F_NOTIFICATION_DATA and then
looking at the data written to figure out whether
you need to poll the vq.


> > kick. If we really want to do, we should try to use page fault handler
> > (probably by extending the config ops), but I'm not sure it's
worth to
> > bother (or if we can find a use case for no simulator devices).
> >
> This need to modify the framework, it seems unworthy.
>
> > >
> > > This cap is disabled as default, users can enable it as follow:
> > >    modprobe vdpa_sim notify_passthrough=true
> > >
> > > Signed-off-by: Longpeng <longpeng2 at 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
> >
> > What's the reason for using uc memory?
> >
> The vma->vm_page_prot of notify mapping is pgprot_noncached (see
> vhost_vdpa_fault) but the vdpasim->notify is WB, so we should set its
> memtype to UC here and set it back to WB when releasing the device.

You never look at this memory though. Why does it matter whether
it's UC or WB?

> > > +       }
> > > +
> > >          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;
> >
> > So we should keep the two paths to be used at the same time. Userspace
> > can choose to not map doorbells?
> >
> It can work even if the userspace does not to map doorbells (e.g start
> without page-per-vq=on), because the device will periodic check its vqs.
>
> > Thanks
> >
> > > +
> > >          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
> > >
> >
> > .