linux-kernel - Re: [virtio-dev] Re: [PATCH v2 4/5] virtio-mmio: add MSI interrupt feature support

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Date:   Thu, 13 Feb 2020 11:40:37 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     "Liu, Jing2" <jing2.liu@...ux.intel.com>,
        Zha Bin <zhabin@...ux.alibaba.com>,
        linux-kernel@...r.kernel.org, virtio-dev@...ts.oasis-open.org,
        slp@...hat.com, qemu-devel@...gnu.org, chao.p.peng@...ux.intel.com,
        gerry@...ux.alibaba.com
Subject: Re: [virtio-dev] Re: [PATCH v2 4/5] virtio-mmio: add MSI interrupt
 feature support


On 2020/2/12 下午5:16, Michael S. Tsirkin wrote:
>>> Thanks for the advice.:)
>>>
>>> Actually when looking into pci, the queue_msix_vector/msix_config is the
>>> msi vector index, which is the same as the mmio register MsiVecSel
>>> (0x0d0).
>>>
>>> So we don't introduce two extra registers for mapping even in sharing
>>> mode.
>>>
>>> What do you think?
>>>
>> I'm not sure I get the point, but I still prefer the separate vector_sel
>> from queue_msix_vector.
>>
>> Btw, Michael propose per vq registers which could also work.
>>
>> Thanks
>>
> Right and I'd even ask a question: do we need shared MSI at all?


I guess it is still needed at least for the current virtio code. 
Technically we may have thousands queues.

Thanks


> Is it somehow better than legacy interrupt? And why?
> Performance numbers please.
>