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;
Date:   Fri, 27 Sep 2019 16:04:10 +0800
From:   Tiwei Bie <tiwei.bie@intel.com>
To:     Jason Wang <jasowang@redhat.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
Subject: Re: [PATCH] vhost: introduce mdev based hardware backend
Message-ID: <20190927080410.GA22568@___>
References: <20190926045427.4973-1-tiwei.bie@intel.com>
 <1b4b8891-8c14-1c85-1d6a-2eed1c90bcde@redhat.com>
 <20190927045438.GA17152@___>
 <49bb0777-3761-3737-8e5b-568957f9a935@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <49bb0777-3761-3737-8e5b-568957f9a935@redhat.com>
User-Agent: Mutt/1.9.4 (2018-02-28)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, Sep 27, 2019 at 03:14:42PM +0800, Jason Wang wrote:
> On 2019/9/27 下午12:54, Tiwei Bie wrote:
> > > > +
> > > > +		/*
> > > > +		 * In vhost-mdev, userspace should pass ring addresses
> > > > +		 * in guest physical addresses when IOMMU is disabled or
> > > > +		 * IOVAs when IOMMU is enabled.
> > > > +		 */
> > > A question here, consider we're using noiommu mode. If guest physical
> > > address is passed here, how can a device use that?
> > > 
> > > I believe you meant "host physical address" here? And it also have the
> > > implication that the HPA should be continuous (e.g using hugetlbfs).
> > The comment is talking about the virtual IOMMU (i.e. iotlb in vhost).
> > It should be rephrased to cover the noiommu case as well. Thanks for
> > spotting this.
> 
> 
> So the question still, if GPA is passed how can it be used by the
> virtio-mdev device?

Sorry if I didn't make it clear..
Of course, GPA can't be passed in noiommu mode.


> 
> Thanks
>