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

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Date:   Mon, 12 Oct 2020 11:17:25 +0300
From:   Eli Cohen <elic@...dia.com>
To:     Jason Wang <jasowang@...hat.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 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?

> 
> 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.
> 
> 
> > 
>