Re: [Qemu-devel] [PATCH V4 net-next] vhost_net: device IOTLB support

[Jason Wang <jasowang@redhat.com>]

On 2017年01月12日 22:17, Michael S. Tsirkin wrote:
> On Wed, Jan 11, 2017 at 12:32:12PM +0800, Jason Wang wrote:
>> This patches implements Device IOTLB support for vhost kernel. This is
>> done through:
>>
>> 1) switch to use dma helpers when map/unmap vrings from vhost codes
>> 2) introduce a set of VhostOps to:
>>     - setting up device IOTLB request callback
>>     - processing device IOTLB request
>>     - processing device IOTLB invalidation
>> 2) kernel support for Device IOTLB API:
>>
>> - allow vhost-net to query the IOMMU IOTLB entry through eventfd
>> - enable the ability for qemu to update a specified mapping of vhost
>> - through ioctl.
>> - enable the ability to invalidate a specified range of iova for the
>>    device IOTLB of vhost through ioctl. In x86/intel_iommu case this is
>>    triggered through iommu memory region notifier from device IOTLB
>>    invalidation descriptor processing routine.
>>
>> With all the above, kernel vhost_net can co-operate with userspace
>> IOMMU. For vhost-user, the support could be easily done on top by
>> implementing the VhostOps.
>>
>> Cc: Michael S. Tsirkin<mst@redhat.com>
>> Signed-off-by: Jason Wang<jasowang@redhat.com>
> Applied, thanks!
>
>> ---
>> Changes from V4:
>> - set iotlb callback only when IOMMU_PLATFORM is negotiated (fix
>>    vhost-user qtest failure)
> In fact this only checks virtio_host_has_feature - which is
> the right thing to do, we can't trust the guest.
>
>> - whitelist VIRTIO_F_IOMMU_PLATFORM instead of manually add it
>> - keep cpu_physical_memory_map() in vhost_memory_map()
> One further enhancement might be to detect that guest disabled
> iommu (e.g. globally, or using iommu=pt) and disable
> the iotlb to avoid overhead for guests which use DPDK
> for assigned devices but not for vhost.
>
>

Yes, it's in my todo list.

Thanks