Message-ID: <f69f7614-5450-bcce-83c7-c5ec5d3a6149@redhat.com>
Date:   Wed, 1 Mar 2023 11:06:55 +0800
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Subject: Re: [PATCH v4 2/2] vdpasim: support doorbell mapping
Content-Language: en-US
To:     "Longpeng(Mike)" <longpeng2@huawei.com>, mst@redhat.com
Cc:     stefanha@redhat.com, sgarzare@redhat.com, arei.gonglei@huawei.com,
        yechuan@huawei.com, huangzhichao@huawei.com,
        virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, eperezma@redhat.com
References: <20230227091857.2406-1-longpeng2@huawei.com>
 <20230227091857.2406-3-longpeng2@huawei.com>
From:   Jason Wang <jasowang@redhat.com>
In-Reply-To: <20230227091857.2406-3-longpeng2@huawei.com>
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Precedence: bulk


在 2023/2/27 17:18, Longpeng(Mike) 写道:
> From: Longpeng <longpeng2@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.
>
> 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 ).
>
> We can test on QEMU with:
>   -device vhost-vdpa-device-pci,vhostdev=/dev/vhost-vdpa-0,page-per-vq=on
>
> Signed-off-by: Longpeng <longpeng2@huawei.com>


Acked-by: Jason Wang <jasowang@redhat.com>

Thanks


> ---
>   drivers/vdpa/vdpa_sim/vdpa_sim.c | 67 ++++++++++++++++++++++++++++++++
>   drivers/vdpa/vdpa_sim/vdpa_sim.h |  3 ++
>   2 files changed, 70 insertions(+)
>
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> index cb88891b44a8..5a8c820b179f 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)
>   {
> @@ -245,6 +247,28 @@ 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)
>   {
> @@ -286,6 +310,13 @@ 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 = (u16 *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
> +	if (!vdpasim->notify)
> +		goto err_iommu;
> +	WRITE_ONCE(*vdpasim->notify, VDPASIM_NOTIFY_DEFVAL);
> +
>   	vdpasim->config = kzalloc(dev_attr->config_size, GFP_KERNEL);
>   	if (!vdpasim->config)
>   		goto err_iommu;
> @@ -320,6 +351,13 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
>   
>   	vdpasim->vdpa.dma_dev = dev;
>   
> +	/*
> + 	 * Start periodic (every 100ms) notify work, it won't introduce
> + 	 * any overhead if the device is not started.
> +	 */
> +	schedule_delayed_work(&vdpasim->notify_work,
> +			      msecs_to_jiffies(VDPASIM_VRING_POLL_PERIOD));
> +
>   	return vdpasim;
>   
>   err_iommu:
> @@ -671,11 +709,34 @@ 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++) {
> @@ -694,6 +755,8 @@ static void vdpasim_free(struct vdpa_device *vdpa)
>   	kfree(vdpasim->iommu);
>   	kfree(vdpasim->vqs);
>   	kfree(vdpasim->config);
> +	if (vdpasim->notify)
> +		free_page((unsigned long)vdpasim->notify);
>   }
>   
>   static const struct vdpa_config_ops vdpasim_config_ops = {
> @@ -705,6 +768,8 @@ 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,
> @@ -738,6 +803,8 @@ 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..786e902de0b2 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 */
> +	u16 *notify;
> +	struct delayed_work notify_work;
>   };
>   
>   struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *attr,