Messages in this thread | | | Subject | Re: [PATCH RFC] vhost: basic device IOTLB support | From | Yang Zhang <> | Date | Mon, 4 Jan 2016 09:39:37 +0800 |
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On 2015/12/31 15:13, Jason Wang wrote: > This patch tries to implement an device IOTLB for vhost. This could be > used with for co-operation with userspace(qemu) implementation of > iommu for a secure DMA environment in guest. > > The idea is simple. When vhost meets an IOTLB miss, it will request > the assistance of userspace to do the translation, this is done > through: > > - Fill the translation request in a preset userspace address (This > address is set through ioctl VHOST_SET_IOTLB_REQUEST_ENTRY). > - Notify userspace through eventfd (This eventfd was set through ioctl > VHOST_SET_IOTLB_FD). > > When userspace finishes the translation, it will update the vhost > IOTLB through VHOST_UPDATE_IOTLB ioctl. Userspace is also in charge of > snooping the IOTLB invalidation of IOMMU IOTLB and use > VHOST_UPDATE_IOTLB to invalidate the possible entry in vhost.
Is there any performance data shows the difference with IOTLB supporting? I doubt we may see performance decrease since the flush code path is longer than before.
-- best regards yang
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