netdev - Re: [PATCH V2 2/6] kvm: detect assigned device via irqbypass manager

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Date:   Mon, 20 Jul 2020 15:40:46 +0800
From:   "Zhu, Lingshan" <lingshan.zhu@...el.com>
To:     Jason Wang <jasowang@...hat.com>, mst@...hat.com,
        alex.williamson@...hat.com, pbonzini@...hat.com,
        sean.j.christopherson@...el.com, wanpengli@...cent.com
Cc:     virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH V2 2/6] kvm: detect assigned device via irqbypass manager


On 7/17/2020 12:01 PM, Jason Wang wrote:
>
> On 2020/7/16 下午7:23, Zhu Lingshan wrote:
>> vDPA devices has dedicated backed hardware like
>> passthrough-ed devices. Then it is possible to setup irq
>> offloading to vCPU for vDPA devices. Thus this patch tries to
>> manipulated assigned device counters via irqbypass manager.
>
>
> This part needs some tweak, e.g why assigned device could be detected 
> through this way.
>
>
>>
>> We will increase/decrease the assigned device counter in kvm/x86.
>
>
> And you need explain why we don't need similar thing in other arch.
>
> Thanks
OK Thanks!
>
>
>> Both vDPA and VFIO would go through this code path.
>>
>> This code path only affect x86 for now.
>>
>> Signed-off-by: Zhu Lingshan <lingshan.zhu@...el.com>
>> Suggested-by: Jason Wang <jasowang@...hat.com>
>> ---
>>   arch/x86/kvm/x86.c | 10 ++++++++--
>>   1 file changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 00c88c2..20c07d3 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -10624,11 +10624,17 @@ int kvm_arch_irq_bypass_add_producer(struct 
>> irq_bypass_consumer *cons,
>>   {
>>       struct kvm_kernel_irqfd *irqfd =
>>           container_of(cons, struct kvm_kernel_irqfd, consumer);
>> +    int ret;
>>         irqfd->producer = prod;
>> +    kvm_arch_start_assignment(irqfd->kvm);
>> +    ret = kvm_x86_ops.update_pi_irte(irqfd->kvm,
>> +                     prod->irq, irqfd->gsi, 1);
>> +
>> +    if (ret)
>> +        kvm_arch_end_assignment(irqfd->kvm);
>>   -    return kvm_x86_ops.update_pi_irte(irqfd->kvm,
>> -                       prod->irq, irqfd->gsi, 1);
>> +    return ret;
>>   }
>>     void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer 
>> *cons,
>