Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH v2] vhost: introduce mdev based hardware backend
From:   Jason Wang <jasowang@redhat.com>
To:     Tiwei Bie <tiwei.bie@intel.com>
Cc:     mst@redhat.com, alex.williamson@redhat.com,
        maxime.coquelin@redhat.com, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
        netdev@vger.kernel.org, dan.daly@intel.com,
        cunming.liang@intel.com, zhihong.wang@intel.com,
        lingshan.zhu@intel.com
References: <47a572fd-5597-1972-e177-8ee25ca51247@redhat.com>
 <20191023030253.GA15401@___>
 <ac36f1e3-b972-71ac-fe0c-3db03e016dcf@redhat.com>
 <20191023070747.GA30533@___>
 <106834b5-dae5-82b2-0f97-16951709d075@redhat.com> <20191023101135.GA6367@___>
 <5a7bc5da-d501-2750-90bf-545dd55f85fa@redhat.com>
 <20191024042155.GA21090@___>
 <d37529e1-5147-bbe5-cb9d-299bd6d4aa1a@redhat.com>
 <d4cc4f4e-2635-4041-2f68-cd043a97f25a@redhat.com>
 <20191024091839.GA17463@___>
 <fefc82a3-a137-bc03-e1c3-8de79b238080@redhat.com>
Message-ID: <e7e239ba-2461-4f8d-7dd7-0f557ac7f4bf@redhat.com>
Date:   Fri, 25 Oct 2019 17:54:55 +0800
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.8.0
MIME-Version: 1.0
In-Reply-To: <fefc82a3-a137-bc03-e1c3-8de79b238080@redhat.com>
Content-Language: en-US
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: quoted-printable
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 2019/10/24 =E4=B8=8B=E5=8D=886:42, Jason Wang wrote:
>
> Yes.
>
>
>> =C2=A0 And we should try to avoid
>> putting ctrl vq and Rx/Tx vqs in the same DMA space to prevent
>> guests having the chance to bypass the host (e.g. QEMU) to
>> setup the backend accelerator directly.
>
>
> That's really good point.=C2=A0 So when "vhost" type is created, parent=
=20
> should assume addr of ctrl_vq is hva.
>
> Thanks


This works for vhost but not virtio since there's no way for virtio=20
kernel driver to differ ctrl_vq with the rest when doing DMA map. One=20
possible solution is to provide DMA domain isolation between virtqueues.=20
Then ctrl vq can use its dedicated DMA domain for the work.

Anyway, this could be done in the future. We can have a version first=20
that doesn't support ctrl_vq.

Thanks