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

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Message-ID: <14fd2bf1-e9c1-a192-bd6c-f1ee5fd227f6@redhat.com>
Date:   Wed, 5 Aug 2020 10:16:16 +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 2020/8/4 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

>
>