linux-kernel - Re: [PATCH vhost next 06/10] vdpa: Add means to communicate vq status on get_vq

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Date:   Thu, 16 Jul 2020 11:21:16 +0300
From:   Eli Cohen <eli@...lanox.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     mst@...hat.com, virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, shahafs@...lanox.com,
        saeedm@...lanox.com, Parav Pandit <parav@...lanox.com>
Subject: Re: [PATCH vhost next 06/10] vdpa: Add means to communicate vq
 status on get_vq_state

On Thu, Jul 16, 2020 at 04:11:00PM +0800, Jason Wang wrote:
> 
> On 2020/7/16 下午3:23, Eli Cohen wrote:
> >Currently, get_vq_state() is used only to pass the available index value
> >of a vq. Extend the struct to return status on the VQ to the caller.
> >For now, define VQ_STATE_NOT_READY. In the future it will be extended to
> >include other infomration.
> >
> >Modify current vdpa driver to update this field.
> >
> >Reviewed-by: Parav Pandit <parav@...lanox.com>
> >Signed-off-by: Eli Cohen <eli@...lanox.com>
> 
> 
> What's the difference between this and get_vq_ready()?
> 
> Thanks
> 

There is no difference. It is just a way to communicate a problem to
with the state of the VQ back to the caller. This is not available now.
I think an asynchronous is preferred but that is not available
currently.
> 
> >---
> >  drivers/vdpa/ifcvf/ifcvf_main.c  | 1 +
> >  drivers/vdpa/vdpa_sim/vdpa_sim.c | 1 +
> >  include/linux/vdpa.h             | 9 +++++++++
> >  3 files changed, 11 insertions(+)
> >
> >diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c b/drivers/vdpa/ifcvf/ifcvf_main.c
> >index 69032ee97824..77e3b3d91167 100644
> >--- a/drivers/vdpa/ifcvf/ifcvf_main.c
> >+++ b/drivers/vdpa/ifcvf/ifcvf_main.c
> >@@ -240,6 +240,7 @@ static void ifcvf_vdpa_get_vq_state(struct vdpa_device *vdpa_dev, u16 qid,
> >  {
> >  	struct ifcvf_hw *vf = vdpa_to_vf(vdpa_dev);
> >+	state->state = vf->vring[qid].ready ? 0 : BIT(VQ_STATE_NOT_READY);
> >  	state->avail_index = ifcvf_get_vq_state(vf, qid);
> >  }
> >diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> >index 599519039f8d..06d974b4bd7b 100644
> >--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
> >+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> >@@ -434,6 +434,7 @@ static void vdpasim_get_vq_state(struct vdpa_device *vdpa, u16 idx,
> >  	struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
> >  	struct vringh *vrh = &vq->vring;
> >+	state->state = vq->ready ? 0 : BIT(VQ_STATE_NOT_READY);
> >  	state->avail_index = vrh->last_avail_idx;
> >  }
> >diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
> >index 7b088bebffe8..bcefa30a3b2f 100644
> >--- a/include/linux/vdpa.h
> >+++ b/include/linux/vdpa.h
> >@@ -27,12 +27,21 @@ struct vdpa_notification_area {
> >  	resource_size_t size;
> >  };
> >+/**
> >+ * Bitmask describing the status of the vq
> >+ */
> >+enum {
> >+	VQ_STATE_NOT_READY = 0,
> >+};
> >+
> >  /**
> >   * vDPA vq_state definition
> >   * @avail_index: available index
> >+ * @state: returned status from get_vq_state
> >   */
> >  struct vdpa_vq_state {
> >  	u16	avail_index;
> >+	u32	state;
> >  };
> >  /**
>