linux-kernel - Re: [RFC PATCH 10/24] vdpa: introduce config operations for associating ASID to a virtqueue group

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Date:   Tue, 13 Oct 2020 13:40:44 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Eli Cohen <elic@...dia.com>
Cc:     mst@...hat.com, lulu@...hat.com, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, rob.miller@...adcom.com,
        lingshan.zhu@...el.com, eperezma@...hat.com, hanand@...inx.com,
        mhabets@...arflare.com, amorenoz@...hat.com,
        maxime.coquelin@...hat.com, stefanha@...hat.com,
        sgarzare@...hat.com
Subject: Re: [RFC PATCH 10/24] vdpa: introduce config operations for
 associating ASID to a virtqueue group


On 2020/10/12 下午4:17, Eli Cohen wrote:
> On Mon, Oct 12, 2020 at 03:45:10PM +0800, Jason Wang wrote:
>>> So in theory we can have several asid's (for different virtqueues), each
>>> one should be followed by a specific set_map call. If this is so, how do
>>> I know if I met all the conditions run my driver? Maybe we need another
>>> callback to let the driver know it should not expect more set_maps().
>>
>> This should work similarly as in the past. Two parts of the work is expected
>> to be done by the driver:
>>
>> 1) store the mapping somewhere (e.g hardware) during set_map()
>> 2) associating mapping with a specific virtqueue
>>
>> The only difference is that more than one mapping is used now.
> ok, so like today, I will always get DRIVER_OK after I got all the
> set_maps(), right?


Yes.

Thanks


>
>> For the issue of more set_maps(), driver should be always ready for the new
>> set_maps() call instead of not expecting new set_maps() since guest memory
>> topology could be changed due to several reasons.
>>
>> Qemu or vhost-vDPA will try their best to avoid the frequency of set_maps()
>> for better performance (e.g through batched IOTLB updating). E.g there
>> should be at most one set_map() during one time of guest booting.
>>
>>