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Date: Tue, 14 Feb 2023 10:05:00 +0800
From: "Longpeng (Mike, Cloud Infrastructure Service Product Dept.)"
<longpeng2@...wei.com>
To: "Michael S. Tsirkin" <mst@...hat.com>,
Jason Wang <jasowang@...hat.com>
CC: <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
在 2023/2/13 20:05, Michael S. Tsirkin 写道:
> 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.
>
I think so.
And WRITE_ONCE seems operate on a variable, but we want write value into
a specific memory location here.
>>> +
>>> 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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