Re: [PATCH V5 1/6] vhost: introduce vhost_vring_call

Re: [PATCH V5 1/6] vhost: introduce vhost_vring_call

[Jason Wang]

On 2020/7/31 下午2:55, Zhu Lingshan wrote:
> This commit introduces struct vhost_vring_call which replaced
> raw struct eventfd_ctx *call_ctx in struct vhost_virtqueue.
> Besides eventfd_ctx, it contains a spin lock and an
> irq_bypass_producer in its structure.
>
> Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
> Suggested-by: Jason Wang <jasowang@redhat.com>
> ---
>   drivers/vhost/vdpa.c  |  4 ++--
>   drivers/vhost/vhost.c | 22 ++++++++++++++++------
>   drivers/vhost/vhost.h |  9 ++++++++-
>   3 files changed, 26 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index a54b60d6623f..df3cf386b0cd 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -96,7 +96,7 @@ static void handle_vq_kick(struct vhost_work *work)
>   static irqreturn_t vhost_vdpa_virtqueue_cb(void *private)
>   {
>   	struct vhost_virtqueue *vq = private;
> -	struct eventfd_ctx *call_ctx = vq->call_ctx;
> +	struct eventfd_ctx *call_ctx = vq->call_ctx.ctx;
>   
>   	if (call_ctx)
>   		eventfd_signal(call_ctx, 1);
> @@ -382,7 +382,7 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
>   		break;
>   
>   	case VHOST_SET_VRING_CALL:
> -		if (vq->call_ctx) {
> +		if (vq->call_ctx.ctx) {
>   			cb.callback = vhost_vdpa_virtqueue_cb;
>   			cb.private = vq;
>   		} else {
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index d7b8df3edffc..9f1a845a9302 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -298,6 +298,13 @@ static void vhost_vq_meta_reset(struct vhost_dev *d)
>   		__vhost_vq_meta_reset(d->vqs[i]);
>   }
>   
> +static void vhost_vring_call_reset(struct vhost_vring_call *call_ctx)
> +{
> +	call_ctx->ctx = NULL;
> +	memset(&call_ctx->producer, 0x0, sizeof(struct irq_bypass_producer));
> +	spin_lock_init(&call_ctx->ctx_lock);
> +}
> +
>   static void vhost_vq_reset(struct vhost_dev *dev,
>   			   struct vhost_virtqueue *vq)
>   {
> @@ -319,13 +326,13 @@ static void vhost_vq_reset(struct vhost_dev *dev,
>   	vq->log_base = NULL;
>   	vq->error_ctx = NULL;
>   	vq->kick = NULL;
> -	vq->call_ctx = NULL;
>   	vq->log_ctx = NULL;
>   	vhost_reset_is_le(vq);
>   	vhost_disable_cross_endian(vq);
>   	vq->busyloop_timeout = 0;
>   	vq->umem = NULL;
>   	vq->iotlb = NULL;
> +	vhost_vring_call_reset(&vq->call_ctx);
>   	__vhost_vq_meta_reset(vq);
>   }
>   
> @@ -685,8 +692,8 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
>   			eventfd_ctx_put(dev->vqs[i]->error_ctx);
>   		if (dev->vqs[i]->kick)
>   			fput(dev->vqs[i]->kick);
> -		if (dev->vqs[i]->call_ctx)
> -			eventfd_ctx_put(dev->vqs[i]->call_ctx);
> +		if (dev->vqs[i]->call_ctx.ctx)
> +			eventfd_ctx_put(dev->vqs[i]->call_ctx.ctx);
>   		vhost_vq_reset(dev, dev->vqs[i]);
>   	}
>   	vhost_dev_free_iovecs(dev);
> @@ -1629,7 +1636,10 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
>   			r = PTR_ERR(ctx);
>   			break;
>   		}
> -		swap(ctx, vq->call_ctx);
> +
> +		spin_lock(&vq->call_ctx.ctx_lock);
> +		swap(ctx, vq->call_ctx.ctx);
> +		spin_unlock(&vq->call_ctx.ctx_lock);
>   		break;
>   	case VHOST_SET_VRING_ERR:
>   		if (copy_from_user(&f, argp, sizeof f)) {
> @@ -2440,8 +2450,8 @@ static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
>   void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
>   {
>   	/* Signal the Guest tell them we used something up. */
> -	if (vq->call_ctx && vhost_notify(dev, vq))
> -		eventfd_signal(vq->call_ctx, 1);
> +	if (vq->call_ctx.ctx && vhost_notify(dev, vq))
> +		eventfd_signal(vq->call_ctx.ctx, 1);
>   }
>   EXPORT_SYMBOL_GPL(vhost_signal);
>   
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index c8e96a095d3b..38eb1aa3b68d 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -13,6 +13,7 @@
>   #include <linux/virtio_ring.h>
>   #include <linux/atomic.h>
>   #include <linux/vhost_iotlb.h>
> +#include <linux/irqbypass.h>
>   
>   struct vhost_work;
>   typedef void (*vhost_work_fn_t)(struct vhost_work *work);
> @@ -60,6 +61,12 @@ enum vhost_uaddr_type {
>   	VHOST_NUM_ADDRS = 3,
>   };
>   
> +struct vhost_vring_call {
> +	struct eventfd_ctx *ctx;
> +	struct irq_bypass_producer producer;
> +	spinlock_t ctx_lock;


It's not clear to me why we need ctx_lock here.

Thanks


> +};
> +
>   /* The virtqueue structure describes a queue attached to a device. */
>   struct vhost_virtqueue {
>   	struct vhost_dev *dev;
> @@ -72,7 +79,7 @@ struct vhost_virtqueue {
>   	vring_used_t __user *used;
>   	const struct vhost_iotlb_map *meta_iotlb[VHOST_NUM_ADDRS];
>   	struct file *kick;
> -	struct eventfd_ctx *call_ctx;
> +	struct vhost_vring_call call_ctx;
>   	struct eventfd_ctx *error_ctx;
>   	struct eventfd_ctx *log_ctx;
>   

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Re: [PATCH V5 1/6] vhost: introduce vhost_vring_call

[Jason Wang]

On 2020/8/4 下午4:42, Zhu, Lingshan wrote:
>
>
> On 8/4/2020 4:38 PM, Jason Wang wrote:
>>
>> On 2020/7/31 下午2:55, Zhu Lingshan wrote:
>>> This commit introduces struct vhost_vring_call which replaced
>>> raw struct eventfd_ctx *call_ctx in struct vhost_virtqueue.
>>> Besides eventfd_ctx, it contains a spin lock and an
>>> irq_bypass_producer in its structure.
>>>
>>> Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
>>> Suggested-by: Jason Wang <jasowang@redhat.com>
>>> ---
>>>   drivers/vhost/vdpa.c  |  4 ++--
>>>   drivers/vhost/vhost.c | 22 ++++++++++++++++------
>>>   drivers/vhost/vhost.h |  9 ++++++++-
>>>   3 files changed, 26 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
>>> index a54b60d6623f..df3cf386b0cd 100644
>>> --- a/drivers/vhost/vdpa.c
>>> +++ b/drivers/vhost/vdpa.c
>>> @@ -96,7 +96,7 @@ static void handle_vq_kick(struct vhost_work *work)
>>>   static irqreturn_t vhost_vdpa_virtqueue_cb(void *private)
>>>   {
>>>       struct vhost_virtqueue *vq = private;
>>> -    struct eventfd_ctx *call_ctx = vq->call_ctx;
>>> +    struct eventfd_ctx *call_ctx = vq->call_ctx.ctx;
>>>         if (call_ctx)
>>>           eventfd_signal(call_ctx, 1);
>>> @@ -382,7 +382,7 @@ static long vhost_vdpa_vring_ioctl(struct 
>>> vhost_vdpa *v, unsigned int cmd,
>>>           break;
>>>         case VHOST_SET_VRING_CALL:
>>> -        if (vq->call_ctx) {
>>> +        if (vq->call_ctx.ctx) {
>>>               cb.callback = vhost_vdpa_virtqueue_cb;
>>>               cb.private = vq;
>>>           } else {
>>> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>>> index d7b8df3edffc..9f1a845a9302 100644
>>> --- a/drivers/vhost/vhost.c
>>> +++ b/drivers/vhost/vhost.c
>>> @@ -298,6 +298,13 @@ static void vhost_vq_meta_reset(struct 
>>> vhost_dev *d)
>>>           __vhost_vq_meta_reset(d->vqs[i]);
>>>   }
>>>   +static void vhost_vring_call_reset(struct vhost_vring_call 
>>> *call_ctx)
>>> +{
>>> +    call_ctx->ctx = NULL;
>>> +    memset(&call_ctx->producer, 0x0, sizeof(struct 
>>> irq_bypass_producer));
>>> +    spin_lock_init(&call_ctx->ctx_lock);
>>> +}
>>> +
>>>   static void vhost_vq_reset(struct vhost_dev *dev,
>>>                  struct vhost_virtqueue *vq)
>>>   {
>>> @@ -319,13 +326,13 @@ static void vhost_vq_reset(struct vhost_dev *dev,
>>>       vq->log_base = NULL;
>>>       vq->error_ctx = NULL;
>>>       vq->kick = NULL;
>>> -    vq->call_ctx = NULL;
>>>       vq->log_ctx = NULL;
>>>       vhost_reset_is_le(vq);
>>>       vhost_disable_cross_endian(vq);
>>>       vq->busyloop_timeout = 0;
>>>       vq->umem = NULL;
>>>       vq->iotlb = NULL;
>>> +    vhost_vring_call_reset(&vq->call_ctx);
>>>       __vhost_vq_meta_reset(vq);
>>>   }
>>>   @@ -685,8 +692,8 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
>>> eventfd_ctx_put(dev->vqs[i]->error_ctx);
>>>           if (dev->vqs[i]->kick)
>>>               fput(dev->vqs[i]->kick);
>>> -        if (dev->vqs[i]->call_ctx)
>>> - eventfd_ctx_put(dev->vqs[i]->call_ctx);
>>> +        if (dev->vqs[i]->call_ctx.ctx)
>>> + eventfd_ctx_put(dev->vqs[i]->call_ctx.ctx);
>>>           vhost_vq_reset(dev, dev->vqs[i]);
>>>       }
>>>       vhost_dev_free_iovecs(dev);
>>> @@ -1629,7 +1636,10 @@ long vhost_vring_ioctl(struct vhost_dev *d, 
>>> unsigned int ioctl, void __user *arg
>>>               r = PTR_ERR(ctx);
>>>               break;
>>>           }
>>> -        swap(ctx, vq->call_ctx);
>>> +
>>> +        spin_lock(&vq->call_ctx.ctx_lock);
>>> +        swap(ctx, vq->call_ctx.ctx);
>>> +        spin_unlock(&vq->call_ctx.ctx_lock);
>>>           break;
>>>       case VHOST_SET_VRING_ERR:
>>>           if (copy_from_user(&f, argp, sizeof f)) {
>>> @@ -2440,8 +2450,8 @@ static bool vhost_notify(struct vhost_dev 
>>> *dev, struct vhost_virtqueue *vq)
>>>   void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
>>>   {
>>>       /* Signal the Guest tell them we used something up. */
>>> -    if (vq->call_ctx && vhost_notify(dev, vq))
>>> -        eventfd_signal(vq->call_ctx, 1);
>>> +    if (vq->call_ctx.ctx && vhost_notify(dev, vq))
>>> +        eventfd_signal(vq->call_ctx.ctx, 1);
>>>   }
>>>   EXPORT_SYMBOL_GPL(vhost_signal);
>>>   diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
>>> index c8e96a095d3b..38eb1aa3b68d 100644
>>> --- a/drivers/vhost/vhost.h
>>> +++ b/drivers/vhost/vhost.h
>>> @@ -13,6 +13,7 @@
>>>   #include <linux/virtio_ring.h>
>>>   #include <linux/atomic.h>
>>>   #include <linux/vhost_iotlb.h>
>>> +#include <linux/irqbypass.h>
>>>     struct vhost_work;
>>>   typedef void (*vhost_work_fn_t)(struct vhost_work *work);
>>> @@ -60,6 +61,12 @@ enum vhost_uaddr_type {
>>>       VHOST_NUM_ADDRS = 3,
>>>   };
>>>   +struct vhost_vring_call {
>>> +    struct eventfd_ctx *ctx;
>>> +    struct irq_bypass_producer producer;
>>> +    spinlock_t ctx_lock;
>>
>>
>> It's not clear to me why we need ctx_lock here.
>>
>> Thanks
> Hi Jason,
>
> we use this lock to protect the eventfd_ctx and irq from race conditions,


We don't support irq notification from vDPA device driver in this 
version, do we still have race condition?

Thanks


>   are you suggesting a better name?
>
> Thanks
>>
>>
>>> +};
>>> +
>>>   /* The virtqueue structure describes a queue attached to a device. */
>>>   struct vhost_virtqueue {
>>>       struct vhost_dev *dev;
>>> @@ -72,7 +79,7 @@ struct vhost_virtqueue {
>>>       vring_used_t __user *used;
>>>       const struct vhost_iotlb_map *meta_iotlb[VHOST_NUM_ADDRS];
>>>       struct file *kick;
>>> -    struct eventfd_ctx *call_ctx;
>>> +    struct vhost_vring_call call_ctx;
>>>       struct eventfd_ctx *error_ctx;
>>>       struct eventfd_ctx *log_ctx;
>>

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Re: [PATCH V5 1/6] vhost: introduce vhost_vring_call

[Michael S. Tsirkin]

On Tue, Aug 04, 2020 at 04:53:39PM +0800, Jason Wang wrote:
> 
> On 2020/8/4 下午4:42, Zhu, Lingshan wrote:
> > 
> > 
> > On 8/4/2020 4:38 PM, Jason Wang wrote:
> > > 
> > > On 2020/7/31 下午2:55, Zhu Lingshan wrote:
> > > > This commit introduces struct vhost_vring_call which replaced
> > > > raw struct eventfd_ctx *call_ctx in struct vhost_virtqueue.
> > > > Besides eventfd_ctx, it contains a spin lock and an
> > > > irq_bypass_producer in its structure.
> > > > 
> > > > Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
> > > > Suggested-by: Jason Wang <jasowang@redhat.com>
> > > > ---
> > > >   drivers/vhost/vdpa.c  |  4 ++--
> > > >   drivers/vhost/vhost.c | 22 ++++++++++++++++------
> > > >   drivers/vhost/vhost.h |  9 ++++++++-
> > > >   3 files changed, 26 insertions(+), 9 deletions(-)
> > > > 
> > > > diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> > > > index a54b60d6623f..df3cf386b0cd 100644
> > > > --- a/drivers/vhost/vdpa.c
> > > > +++ b/drivers/vhost/vdpa.c
> > > > @@ -96,7 +96,7 @@ static void handle_vq_kick(struct vhost_work *work)
> > > >   static irqreturn_t vhost_vdpa_virtqueue_cb(void *private)
> > > >   {
> > > >       struct vhost_virtqueue *vq = private;
> > > > -    struct eventfd_ctx *call_ctx = vq->call_ctx;
> > > > +    struct eventfd_ctx *call_ctx = vq->call_ctx.ctx;
> > > >         if (call_ctx)
> > > >           eventfd_signal(call_ctx, 1);
> > > > @@ -382,7 +382,7 @@ static long vhost_vdpa_vring_ioctl(struct
> > > > vhost_vdpa *v, unsigned int cmd,
> > > >           break;
> > > >         case VHOST_SET_VRING_CALL:
> > > > -        if (vq->call_ctx) {
> > > > +        if (vq->call_ctx.ctx) {
> > > >               cb.callback = vhost_vdpa_virtqueue_cb;
> > > >               cb.private = vq;
> > > >           } else {
> > > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> > > > index d7b8df3edffc..9f1a845a9302 100644
> > > > --- a/drivers/vhost/vhost.c
> > > > +++ b/drivers/vhost/vhost.c
> > > > @@ -298,6 +298,13 @@ static void vhost_vq_meta_reset(struct
> > > > vhost_dev *d)
> > > >           __vhost_vq_meta_reset(d->vqs[i]);
> > > >   }
> > > >   +static void vhost_vring_call_reset(struct vhost_vring_call
> > > > *call_ctx)
> > > > +{
> > > > +    call_ctx->ctx = NULL;
> > > > +    memset(&call_ctx->producer, 0x0, sizeof(struct
> > > > irq_bypass_producer));
> > > > +    spin_lock_init(&call_ctx->ctx_lock);
> > > > +}
> > > > +
> > > >   static void vhost_vq_reset(struct vhost_dev *dev,
> > > >                  struct vhost_virtqueue *vq)
> > > >   {
> > > > @@ -319,13 +326,13 @@ static void vhost_vq_reset(struct vhost_dev *dev,
> > > >       vq->log_base = NULL;
> > > >       vq->error_ctx = NULL;
> > > >       vq->kick = NULL;
> > > > -    vq->call_ctx = NULL;
> > > >       vq->log_ctx = NULL;
> > > >       vhost_reset_is_le(vq);
> > > >       vhost_disable_cross_endian(vq);
> > > >       vq->busyloop_timeout = 0;
> > > >       vq->umem = NULL;
> > > >       vq->iotlb = NULL;
> > > > +    vhost_vring_call_reset(&vq->call_ctx);
> > > >       __vhost_vq_meta_reset(vq);
> > > >   }
> > > >   @@ -685,8 +692,8 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
> > > > eventfd_ctx_put(dev->vqs[i]->error_ctx);
> > > >           if (dev->vqs[i]->kick)
> > > >               fput(dev->vqs[i]->kick);
> > > > -        if (dev->vqs[i]->call_ctx)
> > > > - eventfd_ctx_put(dev->vqs[i]->call_ctx);
> > > > +        if (dev->vqs[i]->call_ctx.ctx)
> > > > + eventfd_ctx_put(dev->vqs[i]->call_ctx.ctx);
> > > >           vhost_vq_reset(dev, dev->vqs[i]);
> > > >       }
> > > >       vhost_dev_free_iovecs(dev);
> > > > @@ -1629,7 +1636,10 @@ long vhost_vring_ioctl(struct vhost_dev
> > > > *d, unsigned int ioctl, void __user *arg
> > > >               r = PTR_ERR(ctx);
> > > >               break;
> > > >           }
> > > > -        swap(ctx, vq->call_ctx);
> > > > +
> > > > +        spin_lock(&vq->call_ctx.ctx_lock);
> > > > +        swap(ctx, vq->call_ctx.ctx);
> > > > +        spin_unlock(&vq->call_ctx.ctx_lock);
> > > >           break;
> > > >       case VHOST_SET_VRING_ERR:
> > > >           if (copy_from_user(&f, argp, sizeof f)) {
> > > > @@ -2440,8 +2450,8 @@ static bool vhost_notify(struct vhost_dev
> > > > *dev, struct vhost_virtqueue *vq)
> > > >   void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
> > > >   {
> > > >       /* Signal the Guest tell them we used something up. */
> > > > -    if (vq->call_ctx && vhost_notify(dev, vq))
> > > > -        eventfd_signal(vq->call_ctx, 1);
> > > > +    if (vq->call_ctx.ctx && vhost_notify(dev, vq))
> > > > +        eventfd_signal(vq->call_ctx.ctx, 1);
> > > >   }
> > > >   EXPORT_SYMBOL_GPL(vhost_signal);
> > > >   diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> > > > index c8e96a095d3b..38eb1aa3b68d 100644
> > > > --- a/drivers/vhost/vhost.h
> > > > +++ b/drivers/vhost/vhost.h
> > > > @@ -13,6 +13,7 @@
> > > >   #include <linux/virtio_ring.h>
> > > >   #include <linux/atomic.h>
> > > >   #include <linux/vhost_iotlb.h>
> > > > +#include <linux/irqbypass.h>
> > > >     struct vhost_work;
> > > >   typedef void (*vhost_work_fn_t)(struct vhost_work *work);
> > > > @@ -60,6 +61,12 @@ enum vhost_uaddr_type {
> > > >       VHOST_NUM_ADDRS = 3,
> > > >   };
> > > >   +struct vhost_vring_call {
> > > > +    struct eventfd_ctx *ctx;
> > > > +    struct irq_bypass_producer producer;
> > > > +    spinlock_t ctx_lock;
> > > 
> > > 
> > > It's not clear to me why we need ctx_lock here.
> > > 
> > > Thanks
> > Hi Jason,
> > 
> > we use this lock to protect the eventfd_ctx and irq from race conditions,
> 
> 
> We don't support irq notification from vDPA device driver in this version,
> do we still have race condition?
> 
> Thanks

Jason I'm not sure what you are trying to say here.


> 
> >   are you suggesting a better name?
> > 
> > Thanks
> > > 
> > > 
> > > > +};
> > > > +
> > > >   /* The virtqueue structure describes a queue attached to a device. */
> > > >   struct vhost_virtqueue {
> > > >       struct vhost_dev *dev;
> > > > @@ -72,7 +79,7 @@ struct vhost_virtqueue {
> > > >       vring_used_t __user *used;
> > > >       const struct vhost_iotlb_map *meta_iotlb[VHOST_NUM_ADDRS];
> > > >       struct file *kick;
> > > > -    struct eventfd_ctx *call_ctx;
> > > > +    struct vhost_vring_call call_ctx;
> > > >       struct eventfd_ctx *error_ctx;
> > > >       struct eventfd_ctx *log_ctx;
> > > 

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Re: [PATCH V5 1/6] vhost: introduce vhost_vring_call

[Jason Wang]

On 2020/8/4 下午5:21, Michael S. Tsirkin wrote:
>>>>>    +struct vhost_vring_call {
>>>>> +    struct eventfd_ctx *ctx;
>>>>> +    struct irq_bypass_producer producer;
>>>>> +    spinlock_t ctx_lock;
>>>> It's not clear to me why we need ctx_lock here.
>>>>
>>>> Thanks
>>> Hi Jason,
>>>
>>> we use this lock to protect the eventfd_ctx and irq from race conditions,
>> We don't support irq notification from vDPA device driver in this version,
>> do we still have race condition?
>>
>> Thanks
> Jason I'm not sure what you are trying to say here.


I meant we change the API from V4 so driver won't notify us if irq is 
changed.

Then it looks to me there's no need for the ctx_lock, everyhing could be 
synchronized with vq mutex.

Thanks

>
>

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Re: [PATCH V5 1/6] vhost: introduce vhost_vring_call

[Jason Wang]

On 2020/8/5 下午1:49, Zhu, Lingshan wrote:
>
>
> On 8/5/2020 10:16 AM, Jason Wang wrote:
>>
>> On 2020/8/4 下午5:21, Michael S. Tsirkin wrote:
>>>>>>>    +struct vhost_vring_call {
>>>>>>> +    struct eventfd_ctx *ctx;
>>>>>>> +    struct irq_bypass_producer producer;
>>>>>>> +    spinlock_t ctx_lock;
>>>>>> It's not clear to me why we need ctx_lock here.
>>>>>>
>>>>>> Thanks
>>>>> Hi Jason,
>>>>>
>>>>> we use this lock to protect the eventfd_ctx and irq from race 
>>>>> conditions,
>>>> We don't support irq notification from vDPA device driver in this 
>>>> version,
>>>> do we still have race condition?
>>>>
>>>> Thanks
>>> Jason I'm not sure what you are trying to say here.
>>
>>
>> I meant we change the API from V4 so driver won't notify us if irq is 
>> changed.
>>
>> Then it looks to me there's no need for the ctx_lock, everyhing could 
>> be synchronized with vq mutex.
>>
>> Thanks
> from V4 to V5, there are only some minor improvements and bug fix, get_vq_irq() almost stays untouched, mutex can work for this, however I see the vq mutex is used in many scenarios.
> We only use this lock to protect the producer information, can this help to get less coupling, defensive code for less bugs?


I think not, vq mutex is used to protect all vq related data structure, 
introducing another one will increase the complexity.

Thanks


>
> Thanks
>>
>>>
>>>
>>

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Re: [PATCH V5 1/6] vhost: introduce vhost_vring_call

[Michael S. Tsirkin]

On Wed, Aug 05, 2020 at 10:16:16AM +0800, Jason Wang wrote:
> 
> On 2020/8/4 下午5:21, Michael S. Tsirkin wrote:
> > > > > >    +struct vhost_vring_call {
> > > > > > +    struct eventfd_ctx *ctx;
> > > > > > +    struct irq_bypass_producer producer;
> > > > > > +    spinlock_t ctx_lock;
> > > > > It's not clear to me why we need ctx_lock here.
> > > > > 
> > > > > Thanks
> > > > Hi Jason,
> > > > 
> > > > we use this lock to protect the eventfd_ctx and irq from race conditions,
> > > We don't support irq notification from vDPA device driver in this version,
> > > do we still have race condition?
> > > 
> > > Thanks
> > Jason I'm not sure what you are trying to say here.
> 
> 
> I meant we change the API from V4 so driver won't notify us if irq is
> changed.
> 
> Then it looks to me there's no need for the ctx_lock, everyhing could be
> synchronized with vq mutex.
> 
> Thanks

Jason do you want to post a cleanup patch simplifying code along these
lines?

Thanks,


> > 
> > 

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Re: [PATCH V5 1/6] vhost: introduce vhost_vring_call

[Jason Wang]

On 2020/8/10 下午9:37, Michael S. Tsirkin wrote:
> On Wed, Aug 05, 2020 at 10:16:16AM +0800, Jason Wang wrote:
>> On 2020/8/4 下午5:21, Michael S. Tsirkin wrote:
>>>>>>>     +struct vhost_vring_call {
>>>>>>> +    struct eventfd_ctx *ctx;
>>>>>>> +    struct irq_bypass_producer producer;
>>>>>>> +    spinlock_t ctx_lock;
>>>>>> It's not clear to me why we need ctx_lock here.
>>>>>>
>>>>>> Thanks
>>>>> Hi Jason,
>>>>>
>>>>> we use this lock to protect the eventfd_ctx and irq from race conditions,
>>>> We don't support irq notification from vDPA device driver in this version,
>>>> do we still have race condition?
>>>>
>>>> Thanks
>>> Jason I'm not sure what you are trying to say here.
>>
>> I meant we change the API from V4 so driver won't notify us if irq is
>> changed.
>>
>> Then it looks to me there's no need for the ctx_lock, everyhing could be
>> synchronized with vq mutex.
>>
>> Thanks
> Jason do you want to post a cleanup patch simplifying code along these
> lines?


Ling Shan promised to post a patch to fix this.

Thanks


>
> Thanks,
>
>
>>>

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Re: [PATCH V5 1/6] vhost: introduce vhost_vring_call

[Jason Wang]

On 2020/8/4 下午5:21, Zhu, Lingshan wrote:
>>> Hi Jason,
>>>
>>> we use this lock to protect the eventfd_ctx and irq from race 
>>> conditions,
>>
>>
>> We don't support irq notification from vDPA device driver in this 
>> version, do we still have race condition?
> as we discussed before:
> (1)if vendor change IRQ after DRIVER_OK, through they should not do this, but they can.
> (2)if user space changes ctx.
>
> Thanks


Yes, but then everything happens in context of syscall (ioctl), so vq 
mutex is sufficient I guess?

Thanks

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Re: [PATCH V5 4/6] vhost_vdpa: implement IRQ offloading in vhost_vdpa

[Jason Wang]

On 2020/7/31 下午2:55, Zhu Lingshan wrote:
> This patch introduce a set of functions for setup/unsetup
> and update irq offloading respectively by register/unregister
> and re-register the irq_bypass_producer.
>
> With these functions, this commit can setup/unsetup
> irq offloading through setting DRIVER_OK/!DRIVER_OK, and
> update irq offloading through SET_VRING_CALL.
>
> Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
> Suggested-by: Jason Wang <jasowang@redhat.com>
> ---
>   drivers/vhost/Kconfig |  1 +
>   drivers/vhost/vdpa.c  | 79 ++++++++++++++++++++++++++++++++++++++++++-
>   2 files changed, 79 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
> index d3688c6afb87..587fbae06182 100644
> --- a/drivers/vhost/Kconfig
> +++ b/drivers/vhost/Kconfig
> @@ -65,6 +65,7 @@ config VHOST_VDPA
>   	tristate "Vhost driver for vDPA-based backend"
>   	depends on EVENTFD
>   	select VHOST
> +	select IRQ_BYPASS_MANAGER
>   	depends on VDPA
>   	help
>   	  This kernel module can be loaded in host kernel to accelerate
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index df3cf386b0cd..278ea2f00172 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -115,6 +115,55 @@ static irqreturn_t vhost_vdpa_config_cb(void *private)
>   	return IRQ_HANDLED;
>   }
>   
> +static void vhost_vdpa_setup_vq_irq(struct vhost_vdpa *v, u16 qid)
> +{
> +	struct vhost_virtqueue *vq = &v->vqs[qid];
> +	const struct vdpa_config_ops *ops = v->vdpa->config;
> +	struct vdpa_device *vdpa = v->vdpa;
> +	int ret, irq;
> +
> +	spin_lock(&vq->call_ctx.ctx_lock);
> +	irq = ops->get_vq_irq(vdpa, qid);
> +	if (!vq->call_ctx.ctx || irq < 0) {
> +		spin_unlock(&vq->call_ctx.ctx_lock);
> +		return;
> +	}
> +
> +	vq->call_ctx.producer.token = vq->call_ctx.ctx;
> +	vq->call_ctx.producer.irq = irq;
> +	ret = irq_bypass_register_producer(&vq->call_ctx.producer);
> +	spin_unlock(&vq->call_ctx.ctx_lock);
> +}
> +
> +static void vhost_vdpa_unsetup_vq_irq(struct vhost_vdpa *v, u16 qid)
> +{
> +	struct vhost_virtqueue *vq = &v->vqs[qid];
> +
> +	spin_lock(&vq->call_ctx.ctx_lock);
> +	irq_bypass_unregister_producer(&vq->call_ctx.producer);


Any reason for not checking vq->call_ctx.producer.irq as below here?


> +	spin_unlock(&vq->call_ctx.ctx_lock);
> +}
> +
> +static void vhost_vdpa_update_vq_irq(struct vhost_virtqueue *vq)
> +{
> +	spin_lock(&vq->call_ctx.ctx_lock);
> +	/*
> +	 * if it has a non-zero irq, means there is a
> +	 * previsouly registered irq_bypass_producer,
> +	 * we should update it when ctx (its token)
> +	 * changes.
> +	 */
> +	if (!vq->call_ctx.producer.irq) {
> +		spin_unlock(&vq->call_ctx.ctx_lock);
> +		return;
> +	}
> +
> +	irq_bypass_unregister_producer(&vq->call_ctx.producer);
> +	vq->call_ctx.producer.token = vq->call_ctx.ctx;
> +	irq_bypass_register_producer(&vq->call_ctx.producer);
> +	spin_unlock(&vq->call_ctx.ctx_lock);
> +}


I think setup_irq() and update_irq() could be unified with the following 
logic:

irq_bypass_unregister_producer(&vq->call_ctx.producer);
irq = ops->get_vq_irq(vdpa, qid);
     if (!vq->call_ctx.ctx || irq < 0) {
         spin_unlock(&vq->call_ctx.ctx_lock);
         return;
     }

vq->call_ctx.producer.token = vq->call_ctx.ctx;
vq->call_ctx.producer.irq = irq;
ret = irq_bypass_register_producer(&vq->call_ctx.producer);

> +
>   static void vhost_vdpa_reset(struct vhost_vdpa *v)
>   {
>   	struct vdpa_device *vdpa = v->vdpa;
> @@ -155,11 +204,15 @@ static long vhost_vdpa_set_status(struct vhost_vdpa *v, u8 __user *statusp)
>   {
>   	struct vdpa_device *vdpa = v->vdpa;
>   	const struct vdpa_config_ops *ops = vdpa->config;
> -	u8 status;
> +	u8 status, status_old;
> +	int nvqs = v->nvqs;
> +	u16 i;
>   
>   	if (copy_from_user(&status, statusp, sizeof(status)))
>   		return -EFAULT;
>   
> +	status_old = ops->get_status(vdpa);
> +
>   	/*
>   	 * Userspace shouldn't remove status bits unless reset the
>   	 * status to 0.
> @@ -169,6 +222,15 @@ static long vhost_vdpa_set_status(struct vhost_vdpa *v, u8 __user *statusp)
>   
>   	ops->set_status(vdpa, status);
>   
> +	/* vq irq is not expected to be changed once DRIVER_OK is set */


Let's move this comment to the get_vq_irq bus operation.


> +	if ((status & VIRTIO_CONFIG_S_DRIVER_OK) && !(status_old & VIRTIO_CONFIG_S_DRIVER_OK))
> +		for (i = 0; i < nvqs; i++)
> +			vhost_vdpa_setup_vq_irq(v, i);
> +
> +	if ((status_old & VIRTIO_CONFIG_S_DRIVER_OK) && !(status & VIRTIO_CONFIG_S_DRIVER_OK))
> +		for (i = 0; i < nvqs; i++)
> +			vhost_vdpa_unsetup_vq_irq(v, i);
> +
>   	return 0;
>   }
>   
> @@ -332,6 +394,7 @@ static long vhost_vdpa_set_config_call(struct vhost_vdpa *v, u32 __user *argp)
>   
>   	return 0;
>   }
> +
>   static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
>   				   void __user *argp)
>   {
> @@ -390,6 +453,7 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
>   			cb.private = NULL;
>   		}
>   		ops->set_vq_cb(vdpa, idx, &cb);
> +		vhost_vdpa_update_vq_irq(vq);
>   		break;
>   
>   	case VHOST_SET_VRING_NUM:
> @@ -765,6 +829,18 @@ static int vhost_vdpa_open(struct inode *inode, struct file *filep)
>   	return r;
>   }
>   
> +static void vhost_vdpa_clean_irq(struct vhost_vdpa *v)
> +{
> +	struct vhost_virtqueue *vq;
> +	int i;
> +
> +	for (i = 0; i < v->nvqs; i++) {
> +		vq = &v->vqs[i];
> +		if (vq->call_ctx.producer.irq)
> +			irq_bypass_unregister_producer(&vq->call_ctx.producer);
> +	}
> +}


Why not using vhost_vdpa_unsetup_vq_irq()?

Thanks


> +
>   static int vhost_vdpa_release(struct inode *inode, struct file *filep)
>   {
>   	struct vhost_vdpa *v = filep->private_data;
> @@ -777,6 +853,7 @@ static int vhost_vdpa_release(struct inode *inode, struct file *filep)
>   	vhost_vdpa_iotlb_free(v);
>   	vhost_vdpa_free_domain(v);
>   	vhost_vdpa_config_put(v);
> +	vhost_vdpa_clean_irq(v);
>   	vhost_dev_cleanup(&v->vdev);
>   	kfree(v->vdev.vqs);
>   	mutex_unlock(&d->mutex);

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Re: [PATCH V5 4/6] vhost_vdpa: implement IRQ offloading in vhost_vdpa

[Michael S. Tsirkin]

On Tue, Aug 04, 2020 at 05:31:38PM +0800, Zhu, Lingshan wrote:
> 
> On 8/4/2020 4:51 PM, Jason Wang wrote:
> 
> 
>     On 2020/7/31 下午2:55, Zhu Lingshan wrote:
> 
>         This patch introduce a set of functions for setup/unsetup
>         and update irq offloading respectively by register/unregister
>         and re-register the irq_bypass_producer.
> 
>         With these functions, this commit can setup/unsetup
>         irq offloading through setting DRIVER_OK/!DRIVER_OK, and
>         update irq offloading through SET_VRING_CALL.
> 
>         Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
>         Suggested-by: Jason Wang <jasowang@redhat.com>
>         ---
>           drivers/vhost/Kconfig |  1 +
>           drivers/vhost/vdpa.c  | 79
>         ++++++++++++++++++++++++++++++++++++++++++-
>           2 files changed, 79 insertions(+), 1 deletion(-)
> 
>         diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
>         index d3688c6afb87..587fbae06182 100644
>         --- a/drivers/vhost/Kconfig
>         +++ b/drivers/vhost/Kconfig
>         @@ -65,6 +65,7 @@ config VHOST_VDPA
>               tristate "Vhost driver for vDPA-based backend"
>               depends on EVENTFD
>               select VHOST
>         +    select IRQ_BYPASS_MANAGER
>               depends on VDPA
>               help
>                 This kernel module can be loaded in host kernel to accelerate
>         diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
>         index df3cf386b0cd..278ea2f00172 100644
>         --- a/drivers/vhost/vdpa.c
>         +++ b/drivers/vhost/vdpa.c
>         @@ -115,6 +115,55 @@ static irqreturn_t vhost_vdpa_config_cb(void
>         *private)
>               return IRQ_HANDLED;
>           }
>           +static void vhost_vdpa_setup_vq_irq(struct vhost_vdpa *v, u16 qid)
>         +{
>         +    struct vhost_virtqueue *vq = &v->vqs[qid];
>         +    const struct vdpa_config_ops *ops = v->vdpa->config;
>         +    struct vdpa_device *vdpa = v->vdpa;
>         +    int ret, irq;
>         +
>         +    spin_lock(&vq->call_ctx.ctx_lock);
>         +    irq = ops->get_vq_irq(vdpa, qid);
>         +    if (!vq->call_ctx.ctx || irq < 0) {
>         +        spin_unlock(&vq->call_ctx.ctx_lock);
>         +        return;
>         +    }
>         +
>         +    vq->call_ctx.producer.token = vq->call_ctx.ctx;
>         +    vq->call_ctx.producer.irq = irq;
>         +    ret = irq_bypass_register_producer(&vq->call_ctx.producer);
>         +    spin_unlock(&vq->call_ctx.ctx_lock);
>         +}
>         +
>         +static void vhost_vdpa_unsetup_vq_irq(struct vhost_vdpa *v, u16 qid)
>         +{
>         +    struct vhost_virtqueue *vq = &v->vqs[qid];
>         +
>         +    spin_lock(&vq->call_ctx.ctx_lock);
>         +    irq_bypass_unregister_producer(&vq->call_ctx.producer);
> 
> 
> 
>     Any reason for not checking vq->call_ctx.producer.irq as below here?
> 
> we only need ctx as a token to unregister vq from irq bypass manager, if vq->call_ctx.producer.irq is 0, means it is a unused or disabled vq, no harm if we
> perform an unregister on it.
> 
> 
> 
>         +    spin_unlock(&vq->call_ctx.ctx_lock);
>         +}
>         +
>         +static void vhost_vdpa_update_vq_irq(struct vhost_virtqueue *vq)
>         +{
>         +    spin_lock(&vq->call_ctx.ctx_lock);
>         +    /*
>         +     * if it has a non-zero irq, means there is a
>         +     * previsouly registered irq_bypass_producer,
>         +     * we should update it when ctx (its token)
>         +     * changes.
>         +     */
>         +    if (!vq->call_ctx.producer.irq) {
>         +        spin_unlock(&vq->call_ctx.ctx_lock);
>         +        return;
>         +    }
>         +
>         +    irq_bypass_unregister_producer(&vq->call_ctx.producer);
>         +    vq->call_ctx.producer.token = vq->call_ctx.ctx;
>         +    irq_bypass_register_producer(&vq->call_ctx.producer);
>         +    spin_unlock(&vq->call_ctx.ctx_lock);
>         +}
> 
> 
> 
>     I think setup_irq() and update_irq() could be unified with the following
>     logic:
> 
>     irq_bypass_unregister_producer(&vq->call_ctx.producer);
>     irq = ops->get_vq_irq(vdpa, qid);
>         if (!vq->call_ctx.ctx || irq < 0) {
>             spin_unlock(&vq->call_ctx.ctx_lock);
>             return;
>         }
> 
>     vq->call_ctx.producer.token = vq->call_ctx.ctx;
>     vq->call_ctx.producer.irq = irq;
>     ret = irq_bypass_register_producer(&vq->call_ctx.producer);
> 
> Yes, this code piece can do both register and update. Though it's rare to call undate_irq(), however
> setup_irq() is very likely to be called for every vq, so this may cause several rounds of useless irq_bypass_unregister_producer().
> is it worth for simplify the code?
> 
> 
>         +
>           static void vhost_vdpa_reset(struct vhost_vdpa *v)
>           {
>               struct vdpa_device *vdpa = v->vdpa;
>         @@ -155,11 +204,15 @@ static long vhost_vdpa_set_status(struct
>         vhost_vdpa *v, u8 __user *statusp)
>           {
>               struct vdpa_device *vdpa = v->vdpa;
>               const struct vdpa_config_ops *ops = vdpa->config;
>         -    u8 status;
>         +    u8 status, status_old;
>         +    int nvqs = v->nvqs;
>         +    u16 i;
>                 if (copy_from_user(&status, statusp, sizeof(status)))
>                   return -EFAULT;
>           +    status_old = ops->get_status(vdpa);
>         +
>               /*
>                * Userspace shouldn't remove status bits unless reset the
>                * status to 0.
>         @@ -169,6 +222,15 @@ static long vhost_vdpa_set_status(struct
>         vhost_vdpa *v, u8 __user *statusp)
>                 ops->set_status(vdpa, status);
>           +    /* vq irq is not expected to be changed once DRIVER_OK is set */
> 
> 
> 
>     Let's move this comment to the get_vq_irq bus operation.
> 
> OK, can do!
> 
> 


Patch on top pls, these are in my tree now.

> 
>         +    if ((status & VIRTIO_CONFIG_S_DRIVER_OK) && !(status_old &
>         VIRTIO_CONFIG_S_DRIVER_OK))
>         +        for (i = 0; i < nvqs; i++)
>         +            vhost_vdpa_setup_vq_irq(v, i);
>         +
>         +    if ((status_old & VIRTIO_CONFIG_S_DRIVER_OK) && !(status &
>         VIRTIO_CONFIG_S_DRIVER_OK))
>         +        for (i = 0; i < nvqs; i++)
>         +            vhost_vdpa_unsetup_vq_irq(v, i);
>         +
>               return 0;
>           }
>           @@ -332,6 +394,7 @@ static long vhost_vdpa_set_config_call(struct
>         vhost_vdpa *v, u32 __user *argp)
>                 return 0;
>           }
>         +
>           static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int
>         cmd,
>                              void __user *argp)
>           {
>         @@ -390,6 +453,7 @@ static long vhost_vdpa_vring_ioctl(struct
>         vhost_vdpa *v, unsigned int cmd,
>                       cb.private = NULL;
>                   }
>                   ops->set_vq_cb(vdpa, idx, &cb);
>         +        vhost_vdpa_update_vq_irq(vq);
>                   break;
>                 case VHOST_SET_VRING_NUM:
>         @@ -765,6 +829,18 @@ static int vhost_vdpa_open(struct inode *inode,
>         struct file *filep)
>               return r;
>           }
>           +static void vhost_vdpa_clean_irq(struct vhost_vdpa *v)
>         +{
>         +    struct vhost_virtqueue *vq;
>         +    int i;
>         +
>         +    for (i = 0; i < v->nvqs; i++) {
>         +        vq = &v->vqs[i];
>         +        if (vq->call_ctx.producer.irq)
>         +            irq_bypass_unregister_producer(&vq->call_ctx.producer);
>         +    }
>         +}
> 
> 
> 
>     Why not using vhost_vdpa_unsetup_vq_irq()?
> 
> IMHO, in this cleanup phase, the device is almost dead, user space won't change ctx anymore, so I think we don't need to check ctx or irq, can just unregister it.
> 
> Thanks!
> 
> 
>     Thanks
> 
> 
> 
>         +
>           static int vhost_vdpa_release(struct inode *inode, struct file
>         *filep)
>           {
>               struct vhost_vdpa *v = filep->private_data;
>         @@ -777,6 +853,7 @@ static int vhost_vdpa_release(struct inode *inode,
>         struct file *filep)
>               vhost_vdpa_iotlb_free(v);
>               vhost_vdpa_free_domain(v);
>               vhost_vdpa_config_put(v);
>         +    vhost_vdpa_clean_irq(v);
>               vhost_dev_cleanup(&v->vdev);
>               kfree(v->vdev.vqs);
>               mutex_unlock(&d->mutex);
> 
> 
> 

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Re: [PATCH V5 4/6] vhost_vdpa: implement IRQ offloading in vhost_vdpa

[Jason Wang]

On 2020/8/4 下午5:31, Zhu, Lingshan wrote:
>
>
> On 8/4/2020 4:51 PM, Jason Wang wrote:
>>
>> On 2020/7/31 下午2:55, Zhu Lingshan wrote:
>>> This patch introduce a set of functions for setup/unsetup
>>> and update irq offloading respectively by register/unregister
>>> and re-register the irq_bypass_producer.
>>>
>>> With these functions, this commit can setup/unsetup
>>> irq offloading through setting DRIVER_OK/!DRIVER_OK, and
>>> update irq offloading through SET_VRING_CALL.
>>>
>>> Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
>>> Suggested-by: Jason Wang <jasowang@redhat.com>
>>> ---
>>>   drivers/vhost/Kconfig |  1 +
>>>   drivers/vhost/vdpa.c  | 79 
>>> ++++++++++++++++++++++++++++++++++++++++++-
>>>   2 files changed, 79 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
>>> index d3688c6afb87..587fbae06182 100644
>>> --- a/drivers/vhost/Kconfig
>>> +++ b/drivers/vhost/Kconfig
>>> @@ -65,6 +65,7 @@ config VHOST_VDPA
>>>       tristate "Vhost driver for vDPA-based backend"
>>>       depends on EVENTFD
>>>       select VHOST
>>> +    select IRQ_BYPASS_MANAGER
>>>       depends on VDPA
>>>       help
>>>         This kernel module can be loaded in host kernel to accelerate
>>> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
>>> index df3cf386b0cd..278ea2f00172 100644
>>> --- a/drivers/vhost/vdpa.c
>>> +++ b/drivers/vhost/vdpa.c
>>> @@ -115,6 +115,55 @@ static irqreturn_t vhost_vdpa_config_cb(void 
>>> *private)
>>>       return IRQ_HANDLED;
>>>   }
>>>   +static void vhost_vdpa_setup_vq_irq(struct vhost_vdpa *v, u16 qid)
>>> +{
>>> +    struct vhost_virtqueue *vq = &v->vqs[qid];
>>> +    const struct vdpa_config_ops *ops = v->vdpa->config;
>>> +    struct vdpa_device *vdpa = v->vdpa;
>>> +    int ret, irq;
>>> +
>>> +    spin_lock(&vq->call_ctx.ctx_lock);
>>> +    irq = ops->get_vq_irq(vdpa, qid);
>>> +    if (!vq->call_ctx.ctx || irq < 0) {
>>> +        spin_unlock(&vq->call_ctx.ctx_lock);
>>> +        return;
>>> +    }
>>> +
>>> +    vq->call_ctx.producer.token = vq->call_ctx.ctx;
>>> +    vq->call_ctx.producer.irq = irq;
>>> +    ret = irq_bypass_register_producer(&vq->call_ctx.producer);
>>> +    spin_unlock(&vq->call_ctx.ctx_lock);
>>> +}
>>> +
>>> +static void vhost_vdpa_unsetup_vq_irq(struct vhost_vdpa *v, u16 qid)
>>> +{
>>> +    struct vhost_virtqueue *vq = &v->vqs[qid];
>>> +
>>> +    spin_lock(&vq->call_ctx.ctx_lock);
>>> + irq_bypass_unregister_producer(&vq->call_ctx.producer);
>>
>>
>> Any reason for not checking vq->call_ctx.producer.irq as below here?
> we only need ctx as a token to unregister vq from irq bypass manager, if vq->call_ctx.producer.irq is 0, means it is a unused or disabled vq,


This is not how the code is wrote? See above you only check whether irq 
is negative, irq 0 seems acceptable.

+    spin_lock(&vq->call_ctx.ctx_lock);
+    irq = ops->get_vq_irq(vdpa, qid);
+    if (!vq->call_ctx.ctx || irq < 0) {
+        spin_unlock(&vq->call_ctx.ctx_lock);
+        return;
+    }
+
+    vq->call_ctx.producer.token = vq->call_ctx.ctx;
+    vq->call_ctx.producer.irq = irq;
+    ret = irq_bypass_register_producer(&vq->call_ctx.producer);
+    spin_unlock(&vq->call_ctx.ctx_lock);


> no harm if we
> perform an unregister on it.
>>
>>
>>> + spin_unlock(&vq->call_ctx.ctx_lock);
>>> +}
>>> +
>>> +static void vhost_vdpa_update_vq_irq(struct vhost_virtqueue *vq)
>>> +{
>>> +    spin_lock(&vq->call_ctx.ctx_lock);
>>> +    /*
>>> +     * if it has a non-zero irq, means there is a
>>> +     * previsouly registered irq_bypass_producer,
>>> +     * we should update it when ctx (its token)
>>> +     * changes.
>>> +     */
>>> +    if (!vq->call_ctx.producer.irq) {
>>> +        spin_unlock(&vq->call_ctx.ctx_lock);
>>> +        return;
>>> +    }
>>> +
>>> + irq_bypass_unregister_producer(&vq->call_ctx.producer);
>>> +    vq->call_ctx.producer.token = vq->call_ctx.ctx;
>>> + irq_bypass_register_producer(&vq->call_ctx.producer);
>>> +    spin_unlock(&vq->call_ctx.ctx_lock);
>>> +}
>>
>>
>> I think setup_irq() and update_irq() could be unified with the 
>> following logic:
>>
>> irq_bypass_unregister_producer(&vq->call_ctx.producer);
>> irq = ops->get_vq_irq(vdpa, qid);
>>     if (!vq->call_ctx.ctx || irq < 0) {
>>         spin_unlock(&vq->call_ctx.ctx_lock);
>>         return;
>>     }
>>
>> vq->call_ctx.producer.token = vq->call_ctx.ctx;
>> vq->call_ctx.producer.irq = irq;
>> ret = irq_bypass_register_producer(&vq->call_ctx.producer);
> Yes, this code piece can do both register and update. Though it's rare to call undate_irq(), however
> setup_irq() is very likely to be called for every vq, so this may cause several rounds of useless irq_bypass_unregister_producer().


I'm not sure I get this but do you have a case for this?


> is it worth for simplify the code?


Less code(bug).


>>
>>> +
>>>   static void vhost_vdpa_reset(struct vhost_vdpa *v)
>>>   {
>>>       struct vdpa_device *vdpa = v->vdpa;
>>> @@ -155,11 +204,15 @@ static long vhost_vdpa_set_status(struct 
>>> vhost_vdpa *v, u8 __user *statusp)
>>>   {
>>>       struct vdpa_device *vdpa = v->vdpa;
>>>       const struct vdpa_config_ops *ops = vdpa->config;
>>> -    u8 status;
>>> +    u8 status, status_old;
>>> +    int nvqs = v->nvqs;
>>> +    u16 i;
>>>         if (copy_from_user(&status, statusp, sizeof(status)))
>>>           return -EFAULT;
>>>   +    status_old = ops->get_status(vdpa);
>>> +
>>>       /*
>>>        * Userspace shouldn't remove status bits unless reset the
>>>        * status to 0.
>>> @@ -169,6 +222,15 @@ static long vhost_vdpa_set_status(struct 
>>> vhost_vdpa *v, u8 __user *statusp)
>>>         ops->set_status(vdpa, status);
>>>   +    /* vq irq is not expected to be changed once DRIVER_OK is set */
>>
>>
>> Let's move this comment to the get_vq_irq bus operation.
> OK, can do!
>>
>>
>>> +    if ((status & VIRTIO_CONFIG_S_DRIVER_OK) && !(status_old & 
>>> VIRTIO_CONFIG_S_DRIVER_OK))
>>> +        for (i = 0; i < nvqs; i++)
>>> +            vhost_vdpa_setup_vq_irq(v, i);
>>> +
>>> +    if ((status_old & VIRTIO_CONFIG_S_DRIVER_OK) && !(status & 
>>> VIRTIO_CONFIG_S_DRIVER_OK))
>>> +        for (i = 0; i < nvqs; i++)
>>> +            vhost_vdpa_unsetup_vq_irq(v, i);
>>> +
>>>       return 0;
>>>   }
>>>   @@ -332,6 +394,7 @@ static long vhost_vdpa_set_config_call(struct 
>>> vhost_vdpa *v, u32 __user *argp)
>>>         return 0;
>>>   }
>>> +
>>>   static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned 
>>> int cmd,
>>>                      void __user *argp)
>>>   {
>>> @@ -390,6 +453,7 @@ static long vhost_vdpa_vring_ioctl(struct 
>>> vhost_vdpa *v, unsigned int cmd,
>>>               cb.private = NULL;
>>>           }
>>>           ops->set_vq_cb(vdpa, idx, &cb);
>>> +        vhost_vdpa_update_vq_irq(vq);
>>>           break;
>>>         case VHOST_SET_VRING_NUM:
>>> @@ -765,6 +829,18 @@ static int vhost_vdpa_open(struct inode *inode, 
>>> struct file *filep)
>>>       return r;
>>>   }
>>>   +static void vhost_vdpa_clean_irq(struct vhost_vdpa *v)
>>> +{
>>> +    struct vhost_virtqueue *vq;
>>> +    int i;
>>> +
>>> +    for (i = 0; i < v->nvqs; i++) {
>>> +        vq = &v->vqs[i];
>>> +        if (vq->call_ctx.producer.irq)
>>> + irq_bypass_unregister_producer(&vq->call_ctx.producer);
>>> +    }
>>> +}
>>
>>
>> Why not using vhost_vdpa_unsetup_vq_irq()?
> IMHO, in this cleanup phase, the device is almost dead, user space won't change ctx anymore, so I think we don't need to check ctx or irq,


But you check irq here? For ctx, irq_bypass_unregister_producer() can do 
the check instead of us.

Thanks


>   can just unregister it.
>
> Thanks!
>>
>> Thanks
>>
>>
>>> +
>>>   static int vhost_vdpa_release(struct inode *inode, struct file 
>>> *filep)
>>>   {
>>>       struct vhost_vdpa *v = filep->private_data;
>>> @@ -777,6 +853,7 @@ static int vhost_vdpa_release(struct inode 
>>> *inode, struct file *filep)
>>>       vhost_vdpa_iotlb_free(v);
>>>       vhost_vdpa_free_domain(v);
>>>       vhost_vdpa_config_put(v);
>>> +    vhost_vdpa_clean_irq(v);
>>>       vhost_dev_cleanup(&v->vdev);
>>>       kfree(v->vdev.vqs);
>>>       mutex_unlock(&d->mutex);
>>

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Re: [PATCH V5 4/6] vhost_vdpa: implement IRQ offloading in vhost_vdpa

[Jason Wang]

On 2020/8/5 下午1:45, Zhu, Lingshan wrote:
>
>
> On 8/5/2020 10:36 AM, Jason Wang wrote:
>>
>> On 2020/8/4 下午5:31, Zhu, Lingshan wrote:
>>>
>>>
>>> On 8/4/2020 4:51 PM, Jason Wang wrote:
>>>>
>>>> On 2020/7/31 下午2:55, Zhu Lingshan wrote:
>>>>> This patch introduce a set of functions for setup/unsetup
>>>>> and update irq offloading respectively by register/unregister
>>>>> and re-register the irq_bypass_producer.
>>>>>
>>>>> With these functions, this commit can setup/unsetup
>>>>> irq offloading through setting DRIVER_OK/!DRIVER_OK, and
>>>>> update irq offloading through SET_VRING_CALL.
>>>>>
>>>>> Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
>>>>> Suggested-by: Jason Wang <jasowang@redhat.com>
>>>>> ---
>>>>>   drivers/vhost/Kconfig |  1 +
>>>>>   drivers/vhost/vdpa.c  | 79 
>>>>> ++++++++++++++++++++++++++++++++++++++++++-
>>>>>   2 files changed, 79 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
>>>>> index d3688c6afb87..587fbae06182 100644
>>>>> --- a/drivers/vhost/Kconfig
>>>>> +++ b/drivers/vhost/Kconfig
>>>>> @@ -65,6 +65,7 @@ config VHOST_VDPA
>>>>>       tristate "Vhost driver for vDPA-based backend"
>>>>>       depends on EVENTFD
>>>>>       select VHOST
>>>>> +    select IRQ_BYPASS_MANAGER
>>>>>       depends on VDPA
>>>>>       help
>>>>>         This kernel module can be loaded in host kernel to accelerate
>>>>> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
>>>>> index df3cf386b0cd..278ea2f00172 100644
>>>>> --- a/drivers/vhost/vdpa.c
>>>>> +++ b/drivers/vhost/vdpa.c
>>>>> @@ -115,6 +115,55 @@ static irqreturn_t vhost_vdpa_config_cb(void 
>>>>> *private)
>>>>>       return IRQ_HANDLED;
>>>>>   }
>>>>>   +static void vhost_vdpa_setup_vq_irq(struct vhost_vdpa *v, u16 qid)
>>>>> +{
>>>>> +    struct vhost_virtqueue *vq = &v->vqs[qid];
>>>>> +    const struct vdpa_config_ops *ops = v->vdpa->config;
>>>>> +    struct vdpa_device *vdpa = v->vdpa;
>>>>> +    int ret, irq;
>>>>> +
>>>>> +    spin_lock(&vq->call_ctx.ctx_lock);
>>>>> +    irq = ops->get_vq_irq(vdpa, qid);
>>>>> +    if (!vq->call_ctx.ctx || irq < 0) {
>>>>> + spin_unlock(&vq->call_ctx.ctx_lock);
>>>>> +        return;
>>>>> +    }
>>>>> +
>>>>> +    vq->call_ctx.producer.token = vq->call_ctx.ctx;
>>>>> +    vq->call_ctx.producer.irq = irq;
>>>>> +    ret = irq_bypass_register_producer(&vq->call_ctx.producer);
>>>>> +    spin_unlock(&vq->call_ctx.ctx_lock);
>>>>> +}
>>>>> +
>>>>> +static void vhost_vdpa_unsetup_vq_irq(struct vhost_vdpa *v, u16 qid)
>>>>> +{
>>>>> +    struct vhost_virtqueue *vq = &v->vqs[qid];
>>>>> +
>>>>> +    spin_lock(&vq->call_ctx.ctx_lock);
>>>>> + irq_bypass_unregister_producer(&vq->call_ctx.producer);
>>>>
>>>>
>>>> Any reason for not checking vq->call_ctx.producer.irq as below here?
>>> we only need ctx as a token to unregister vq from irq bypass 
>>> manager, if vq->call_ctx.producer.irq is 0, means it is a unused or 
>>> disabled vq,
>>
>>
>> This is not how the code is wrote? See above you only check whether 
>> irq is negative, irq 0 seems acceptable.
> Yes, IRQ 0 is valid, so we check whether it is < 0.
>>
>> +    spin_lock(&vq->call_ctx.ctx_lock);
>> +    irq = ops->get_vq_irq(vdpa, qid);
>> +    if (!vq->call_ctx.ctx || irq < 0) {
>> +        spin_unlock(&vq->call_ctx.ctx_lock);
>> +        return;
>> +    }
>> +
>> +    vq->call_ctx.producer.token = vq->call_ctx.ctx;
>> +    vq->call_ctx.producer.irq = irq;
>> +    ret = irq_bypass_register_producer(&vq->call_ctx.producer);
>> +    spin_unlock(&vq->call_ctx.ctx_lock);
>>
>>
>>> no harm if we
>>> perform an unregister on it.
>>>>
>>>>
>>>>> + spin_unlock(&vq->call_ctx.ctx_lock);
>>>>> +}
>>>>> +
>>>>> +static void vhost_vdpa_update_vq_irq(struct vhost_virtqueue *vq)
>>>>> +{
>>>>> +    spin_lock(&vq->call_ctx.ctx_lock);
>>>>> +    /*
>>>>> +     * if it has a non-zero irq, means there is a
>>>>> +     * previsouly registered irq_bypass_producer,
>>>>> +     * we should update it when ctx (its token)
>>>>> +     * changes.
>>>>> +     */
>>>>> +    if (!vq->call_ctx.producer.irq) {
>>>>> + spin_unlock(&vq->call_ctx.ctx_lock);
>>>>> +        return;
>>>>> +    }
>>>>> +
>>>>> + irq_bypass_unregister_producer(&vq->call_ctx.producer);
>>>>> +    vq->call_ctx.producer.token = vq->call_ctx.ctx;
>>>>> + irq_bypass_register_producer(&vq->call_ctx.producer);
>>>>> +    spin_unlock(&vq->call_ctx.ctx_lock);
>>>>> +}
>>>>
>>>>
>>>> I think setup_irq() and update_irq() could be unified with the 
>>>> following logic:
>>>>
>>>> irq_bypass_unregister_producer(&vq->call_ctx.producer);
>>>> irq = ops->get_vq_irq(vdpa, qid);
>>>>     if (!vq->call_ctx.ctx || irq < 0) {
>>>>         spin_unlock(&vq->call_ctx.ctx_lock);
>>>>         return;
>>>>     }
>>>>
>>>> vq->call_ctx.producer.token = vq->call_ctx.ctx;
>>>> vq->call_ctx.producer.irq = irq;
>>>> ret = irq_bypass_register_producer(&vq->call_ctx.producer);
>>> Yes, this code piece can do both register and update. Though it's 
>>> rare to call undate_irq(), however
>>> setup_irq() is very likely to be called for every vq, so this may 
>>> cause several rounds of useless irq_bypass_unregister_producer().
>>
>>
>> I'm not sure I get this but do you have a case for this?
> I mean if we use this routine to setup irq offloading, it is very likely to do a unregister producer for every vq first, but for nothing.


Does it really harm? See vfio_msi_set_vector_signal()


>>
>>
>>> is it worth for simplify the code?
>>
>>
>> Less code(bug).
> I can do this if we are chasing for perfection, however I believe bug number has positive correlation with the complexity in the logic than code lines, if we only merge lines, this may not help.
>>

Well, reduce code duplication is always good and it helps for reviewers.


>>
>>>>
>>>>> +
>>>>>   static void vhost_vdpa_reset(struct vhost_vdpa *v)
>>>>>   {
>>>>>       struct vdpa_device *vdpa = v->vdpa;
>>>>> @@ -155,11 +204,15 @@ static long vhost_vdpa_set_status(struct 
>>>>> vhost_vdpa *v, u8 __user *statusp)
>>>>>   {
>>>>>       struct vdpa_device *vdpa = v->vdpa;
>>>>>       const struct vdpa_config_ops *ops = vdpa->config;
>>>>> -    u8 status;
>>>>> +    u8 status, status_old;
>>>>> +    int nvqs = v->nvqs;
>>>>> +    u16 i;
>>>>>         if (copy_from_user(&status, statusp, sizeof(status)))
>>>>>           return -EFAULT;
>>>>>   +    status_old = ops->get_status(vdpa);
>>>>> +
>>>>>       /*
>>>>>        * Userspace shouldn't remove status bits unless reset the
>>>>>        * status to 0.
>>>>> @@ -169,6 +222,15 @@ static long vhost_vdpa_set_status(struct 
>>>>> vhost_vdpa *v, u8 __user *statusp)
>>>>>         ops->set_status(vdpa, status);
>>>>>   +    /* vq irq is not expected to be changed once DRIVER_OK is 
>>>>> set */
>>>>
>>>>
>>>> Let's move this comment to the get_vq_irq bus operation.
>>> OK, can do!
>>>>
>>>>
>>>>> +    if ((status & VIRTIO_CONFIG_S_DRIVER_OK) && !(status_old & 
>>>>> VIRTIO_CONFIG_S_DRIVER_OK))
>>>>> +        for (i = 0; i < nvqs; i++)
>>>>> +            vhost_vdpa_setup_vq_irq(v, i);
>>>>> +
>>>>> +    if ((status_old & VIRTIO_CONFIG_S_DRIVER_OK) && !(status & 
>>>>> VIRTIO_CONFIG_S_DRIVER_OK))
>>>>> +        for (i = 0; i < nvqs; i++)
>>>>> +            vhost_vdpa_unsetup_vq_irq(v, i);
>>>>> +
>>>>>       return 0;
>>>>>   }
>>>>>   @@ -332,6 +394,7 @@ static long 
>>>>> vhost_vdpa_set_config_call(struct vhost_vdpa *v, u32 __user *argp)
>>>>>         return 0;
>>>>>   }
>>>>> +
>>>>>   static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, 
>>>>> unsigned int cmd,
>>>>>                      void __user *argp)
>>>>>   {
>>>>> @@ -390,6 +453,7 @@ static long vhost_vdpa_vring_ioctl(struct 
>>>>> vhost_vdpa *v, unsigned int cmd,
>>>>>               cb.private = NULL;
>>>>>           }
>>>>>           ops->set_vq_cb(vdpa, idx, &cb);
>>>>> +        vhost_vdpa_update_vq_irq(vq);
>>>>>           break;
>>>>>         case VHOST_SET_VRING_NUM:
>>>>> @@ -765,6 +829,18 @@ static int vhost_vdpa_open(struct inode 
>>>>> *inode, struct file *filep)
>>>>>       return r;
>>>>>   }
>>>>>   +static void vhost_vdpa_clean_irq(struct vhost_vdpa *v)
>>>>> +{
>>>>> +    struct vhost_virtqueue *vq;
>>>>> +    int i;
>>>>> +
>>>>> +    for (i = 0; i < v->nvqs; i++) {
>>>>> +        vq = &v->vqs[i];
>>>>> +        if (vq->call_ctx.producer.irq)
>>>>> + irq_bypass_unregister_producer(&vq->call_ctx.producer);
>>>>> +    }
>>>>> +}
>>>>
>>>>
>>>> Why not using vhost_vdpa_unsetup_vq_irq()?
>>> IMHO, in this cleanup phase, the device is almost dead, user space 
>>> won't change ctx anymore, so I think we don't need to check ctx or irq,
>>
>>
>> But you check irq here? For ctx, irq_bypass_unregister_producer() can 
>> do the check instead of us.
> IMHO, maybe irq does not matter, (1)if the vq not registered to irq bypass manager, producer.irq is not valid, token == NULL, irq_bypass_unregister would no nothing.
> (2)if the vq registered to irq bypass manager, producer.irq is valid, irq_bypass_unregister will do its work based on the token.
> so maybe we can say irq is relative to the token, we may don't need to check irq here.


So you agree to use vhost_vdpa_unsetup_vq_irq()?

Thanks


>
> Thanks!
>>
>> Thanks
>>
>>
>>>   can just unregister it.
>>>
>>> Thanks!
>>>>
>>>> Thanks
>>>>
>>>>
>>>>> +
>>>>>   static int vhost_vdpa_release(struct inode *inode, struct file 
>>>>> *filep)
>>>>>   {
>>>>>       struct vhost_vdpa *v = filep->private_data;
>>>>> @@ -777,6 +853,7 @@ static int vhost_vdpa_release(struct inode 
>>>>> *inode, struct file *filep)
>>>>>       vhost_vdpa_iotlb_free(v);
>>>>>       vhost_vdpa_free_domain(v);
>>>>>       vhost_vdpa_config_put(v);
>>>>> +    vhost_vdpa_clean_irq(v);
>>>>>       vhost_dev_cleanup(&v->vdev);
>>>>>       kfree(v->vdev.vqs);
>>>>>       mutex_unlock(&d->mutex);
>>>>
>>

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Re: [PATCH V5 4/6] vhost_vdpa: implement IRQ offloading in vhost_vdpa

[Jason Wang]

On 2020/7/31 下午2:55, Zhu Lingshan wrote:
> +static void vhost_vdpa_setup_vq_irq(struct vhost_vdpa *v, u16 qid)
> +{
> +	struct vhost_virtqueue *vq = &v->vqs[qid];
> +	const struct vdpa_config_ops *ops = v->vdpa->config;
> +	struct vdpa_device *vdpa = v->vdpa;
> +	int ret, irq;
> +
> +	spin_lock(&vq->call_ctx.ctx_lock);
> +	irq = ops->get_vq_irq(vdpa, qid);


Btw, this assumes that get_vq_irq is mandatory. This looks wrong since 
there's no guarantee that the vDPA device driver can see irq. And this 
break vdpa simulator.

Let's add a check and make it optional by document this assumption in 
the vdpa.h.

Thanks


> +	if (!vq->call_ctx.ctx || irq < 0) {
> +		spin_unlock(&vq->call_ctx.ctx_lock);
> +		return;
> +	}
> +

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