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

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Date:   Fri, 27 Sep 2019 16:31:31 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Tiwei Bie <tiwei.bie@...el.com>
Cc:     mst@...hat.com, alex.williamson@...hat.com,
        maxime.coquelin@...hat.com, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, dan.daly@...el.com,
        cunming.liang@...el.com, zhihong.wang@...el.com,
        lingshan.zhu@...el.com
Subject: Re: [PATCH] vhost: introduce mdev based hardware backend


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
>>