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Jason Wang

2020-Aug-04 08:53 UTC

[PATCH V5 1/6] vhost: introduce vhost_vring_call

On 2020/8/4 ??4:42, Zhu, Lingshan wrote:>
>
> On 8/4/2020 4:38 PM, Jason Wang wrote:
>>
>> On 2020/7/31 ??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 at intel.com>
>>> Suggested-by: Jason Wang <jasowang at 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;
>>

Michael S. Tsirkin

2020-Aug-04 09:21 UTC

head link

[PATCH V5 1/6] vhost: introduce vhost_vring_call

On Tue, Aug 04, 2020 at 04:53:39PM +0800, Jason Wang
wrote:> 
> On 2020/8/4 ??4:42, Zhu, Lingshan wrote:
> > 
> > 
> > On 8/4/2020 4:38 PM, Jason Wang wrote:
> > > 
> > > On 2020/7/31 ??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 at
intel.com>
> > > > Suggested-by: Jason Wang <jasowang at 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;
> > >

Jason Wang

2020-Aug-05 02:16 UTC

head link

[PATCH V5 1/6] vhost: introduce vhost_vring_call

On 2020/8/4 ??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 Wang

2020-Aug-05 05:53 UTC

head link

[PATCH V5 1/6] vhost: introduce vhost_vring_call

On 2020/8/5 ??1:49, Zhu, Lingshan wrote:>
>
> On 8/5/2020 10:16 AM, Jason Wang wrote:
>>
>> On 2020/8/4 ??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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