linux-kernel - Re: [PATCH net V2 4/4] vhost: log dirty page correctly

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Date:   Fri, 14 Dec 2018 10:43:03 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jintack Lim <jintack@...columbia.edu>
Subject: Re: [PATCH net V2 4/4] vhost: log dirty page correctly


On 2018/12/13 下午10:31, Michael S. Tsirkin wrote:
>> Just to make sure I understand this. It looks to me we should:
>>
>> - allow passing GIOVA->GPA through UAPI
>>
>> - cache GIOVA->GPA somewhere but still use GIOVA->HVA in device IOTLB for
>> performance
>>
>> Is this what you suggest?
>>
>> Thanks
> Not really. We already have GPA->HVA, so I suggested a flag to pass
> GIOVA->GPA in the IOTLB.
>
> This has advantages for security since a single table needs
> then to be validated to ensure guest does not corrupt
> QEMU memory.
>

I wonder how much we can gain through this. Currently, qemu IOMMU gives 
GIOVA->GPA mapping, and qemu vhost code will translate GPA to HVA then 
pass GIOVA->HVA to vhost. It looks no difference to me.

Thanks