netdev - Re: [PATCH V5 1/6] vhost: introduce vhost_vring

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Date:   Mon, 10 Aug 2020 09:37:00 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     "Zhu, Lingshan" <lingshan.zhu@...el.com>,
        alex.williamson@...hat.com, pbonzini@...hat.com,
        sean.j.christopherson@...el.com, wanpengli@...cent.com,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        kvm@...r.kernel.org, eli@...lanox.com, shahafs@...lanox.com,
        parav@...lanox.com
Subject: Re: [PATCH V5 1/6] vhost: introduce vhost_vring_call

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,


> > 
> >