Re: [PATCH] vhost: introduce mdev based hardware backend

Jason Wang
2019-09-27T08:31:48Z

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
>>