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Subject: Re: [PATCH] vhost: introduce mdev based hardware backend
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
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 <1b4b8891-8c14-1c85-1d6a-2eed1c90bcde@redhat.com>
 <20190927045438.GA17152@___>
 <49bb0777-3761-3737-8e5b-568957f9a935@redhat.com>
 <20190927080410.GA22568@___>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <cc288a52-dc5e-1a59-6219-8835c898ea73@redhat.com>
Date:   Fri, 27 Sep 2019 16:31:31 +0800
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On 2019/9/27 下午4:04, Tiwei Bie wrote:
> 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.


I see.

Thanks for the confirmation.


>
>
>> Thanks
>>