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From: Jason Wang <jasowang@redhat.com>
To: "Zhu, Lingshan" <lingshan.zhu@intel.com>,
	"Michael S. Tsirkin" <mst@redhat.com>
Cc: alex.williamson@redhat.com, pbonzini@redhat.com,
	sean.j.christopherson@intel.com, wanpengli@tencent.com,
	virtualization@lists.linux-foundation.org,
	netdev@vger.kernel.org, kvm@vger.kernel.org, eli@mellanox.com,
	shahafs@mellanox.com, parav@mellanox.com
Subject: Re: [PATCH V5 1/6] vhost: introduce vhost_vring_call
Date: Wed, 5 Aug 2020 13:53:43 +0800
Message-ID: <aa18c90f-a315-7d40-cdb7-812b98a9c4f4@redhat.com> (raw)
In-Reply-To: <bf10cde9-db86-a1ac-e2a8-363735e49afb@intel.com>


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
>>
>>>
>>>
>>


  parent reply index

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-31  6:55 [PATCH V5 0/6] IRQ offloading for vDPA Zhu Lingshan
2020-07-31  6:55 ` [PATCH V5 1/6] vhost: introduce vhost_vring_call Zhu Lingshan
2020-08-04  8:38   ` Jason Wang
     [not found]     ` <d51dd4e3-7513-c771-104c-b61f9ee70f30@intel.com>
2020-08-04  8:53       ` Jason Wang
2020-08-04  9:21         ` Michael S. Tsirkin
2020-08-05  2:16           ` Jason Wang
     [not found]             ` <bf10cde9-db86-a1ac-e2a8-363735e49afb@intel.com>
2020-08-05  5:53               ` Jason Wang [this message]
2020-08-10 13:37             ` Michael S. Tsirkin
2020-08-11  2:53               ` Jason Wang
     [not found]         ` <4605de34-c426-33d4-714b-e03716d0374c@intel.com>
2020-08-05  2:20           ` Jason Wang
2020-07-31  6:55 ` [PATCH V5 2/6] kvm: detect assigned device via irqbypass manager Zhu Lingshan
2020-07-31  6:55 ` [PATCH V5 3/6] vDPA: add get_vq_irq() in vdpa_config_ops Zhu Lingshan
2020-07-31  6:55 ` [PATCH V5 4/6] vhost_vdpa: implement IRQ offloading in vhost_vdpa Zhu Lingshan
2020-08-04  8:51   ` Jason Wang
     [not found]     ` <ae5385dc-6637-c5a3-b00a-02f66bb9a85f@intel.com>
2020-08-04  9:36       ` Michael S. Tsirkin
2020-08-05  2:36       ` Jason Wang
     [not found]         ` <cb01a490-e9e6-42f5-b6c3-caefa2d91b9f@intel.com>
2020-08-05  5:51           ` Jason Wang
2020-08-05  8:06   ` Jason Wang
2020-08-05  8:12     ` Zhu, Lingshan
2020-07-31  6:55 ` [PATCH V5 5/6] ifcvf: implement vdpa_config_ops.get_vq_irq() Zhu Lingshan
2020-07-31  6:55 ` [PATCH V5 6/6] irqbypass: do not start cons/prod when failed connect Zhu Lingshan

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