netdev - Re: [PATCH 2/2] vDPA/ifcvf: implement doorbell mapping for ifcvf

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Date:   Wed, 28 Apr 2021 16:42:53 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Zhu Lingshan <lingshan.zhu@...el.com>, mst@...hat.com
Cc:     virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] vDPA/ifcvf: implement doorbell mapping for ifcvf


在 2021/4/28 下午4:21, Zhu Lingshan 写道:
> This commit implements doorbell mapping feature for ifcvf.
> This feature maps the notify page to userspace, to eliminate
> vmexit when kick a vq.
>
> Signed-off-by: Zhu Lingshan <lingshan.zhu@...el.com>
> ---
>   drivers/vdpa/ifcvf/ifcvf_main.c | 18 ++++++++++++++++++
>   1 file changed, 18 insertions(+)
>
> diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c b/drivers/vdpa/ifcvf/ifcvf_main.c
> index e48e6b74fe2e..afcb71bc0f51 100644
> --- a/drivers/vdpa/ifcvf/ifcvf_main.c
> +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
> @@ -413,6 +413,23 @@ static int ifcvf_vdpa_get_vq_irq(struct vdpa_device *vdpa_dev,
>   	return vf->vring[qid].irq;
>   }
>   
> +static struct vdpa_notification_area ifcvf_get_vq_notification(struct vdpa_device *vdpa_dev,
> +							       u16 idx)
> +{
> +	struct ifcvf_hw *vf = vdpa_to_vf(vdpa_dev);
> +	struct vdpa_notification_area area;
> +
> +	if (vf->notify_pa % PAGE_SIZE) {
> +		area.addr = 0;
> +		area.size = 0;


We don't need this since:

1) there's a check in the vhost vDPA
2) device is unaware of the bound driver, non page aligned doorbell 
doesn't necessarily meant it can be used

Let's leave those polices to the driver.

Thanks


> +	} else {
> +		area.addr = vf->notify_pa;
> +		area.size = PAGE_SIZE;
> +	}
> +
> +	return area;
> +}
> +
>   /*
>    * IFCVF currently does't have on-chip IOMMU, so not
>    * implemented set_map()/dma_map()/dma_unmap()
> @@ -440,6 +457,7 @@ static const struct vdpa_config_ops ifc_vdpa_ops = {
>   	.get_config	= ifcvf_vdpa_get_config,
>   	.set_config	= ifcvf_vdpa_set_config,
>   	.set_config_cb  = ifcvf_vdpa_set_config_cb,
> +	.get_vq_notification = ifcvf_get_vq_notification,
>   };
>   
>   static int ifcvf_probe(struct pci_dev *pdev, const struct pci_device_id *id)