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Subject: Re: [PATCH v2 19/24] vdpa: make sure set_features in invoked for
 legacy
To:     "Michael S. Tsirkin" <mst@redhat.com>
Cc:     linux-kernel@vger.kernel.org,
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From:   Jason Wang <jasowang@redhat.com>
Message-ID: <bd915b30-0604-da1b-343f-e228bce4d1d8@redhat.com>
Date:   Thu, 6 Aug 2020 11:23:05 +0800
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On 2020/8/5 下午7:40, Michael S. Tsirkin wrote:
> On Wed, Aug 05, 2020 at 02:14:07PM +0800, Jason Wang wrote:
>> On 2020/8/4 上午5:00, Michael S. Tsirkin wrote:
>>> Some legacy guests just assume features are 0 after reset.
>>> We detect that config space is accessed before features are
>>> set and set features to 0 automatically.
>>> Note: some legacy guests might not even access config space, if this is
>>> reported in the field we might need to catch a kick to handle these.
>> I wonder whether it's easier to just support modern device?
>>
>> Thanks
> Well hardware vendors are I think interested in supporting legacy
> guests. Limiting vdpa to modern only would make it uncompetitive.


My understanding is that, IOMMU_PLATFORM is mandatory for hardware vDPA 
to work. So it can only work for modern device ...

Thanks


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