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

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Date:   Tue, 11 Aug 2020 10:53:48 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...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 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,
>
>
>>>