Messages in this thread |  | | Subject | Re: [PATCH] vhost: introduce vDPA based backend | From | Jason Wang <> | Date | Wed, 5 Feb 2020 15:50:14 +0800 |
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On 2020/2/5 下午3:15, Shahaf Shuler wrote: > Wednesday, February 5, 2020 4:03 AM, Tiwei Bie: >> Subject: Re: [PATCH] vhost: introduce vDPA based backend >> >> On Tue, Feb 04, 2020 at 11:30:11AM +0800, Jason Wang wrote: >>> On 2020/1/31 上午11:36, Tiwei Bie wrote: >>>> This patch introduces a vDPA based vhost backend. This backend is >>>> built on top of the same interface defined in virtio-vDPA and >>>> provides a generic vhost interface for userspace to accelerate the >>>> virtio devices in guest. >>>> >>>> This backend is implemented as a vDPA device driver on top of the >>>> same ops used in virtio-vDPA. It will create char device entry named >>>> vhost-vdpa/$vdpa_device_index for userspace to use. Userspace can >>>> use vhost ioctls on top of this char device to setup the backend. >>>> >>>> Signed-off-by: Tiwei Bie <tiwei.bie@intel.com> > [...] > >>>> +static long vhost_vdpa_do_dma_mapping(struct vhost_vdpa *v) { >>>> + /* TODO: fix this */ >>> >>> Before trying to do this it looks to me we need the following during >>> the probe >>> >>> 1) if set_map() is not supported by the vDPA device probe the IOMMU >>> that is supported by the vDPA device >>> 2) allocate IOMMU domain >>> >>> And then: >>> >>> 3) pin pages through GUP and do proper accounting >>> 4) store GPA->HPA mapping in the umem >>> 5) generate diffs of memory table and using IOMMU API to setup the dma >>> mapping in this method >>> >>> For 1), I'm not sure parent is sufficient for to doing this or need to >>> introduce new API like iommu_device in mdev. >> Agree. We may also need to introduce something like the iommu_device. >> > Would it be better for the map/umnap logic to happen inside each device ? > Devices that needs the IOMMU will call iommu APIs from inside the driver callback.
Technically, this can work. But if it can be done by vhost-vpda it will make the vDPA driver more compact and easier to be implemented.
> Devices that has other ways to do the DMA mapping will call the proprietary APIs.
To confirm, do you prefer:
1) map/unmap
or
2) pass all maps at one time?
Thanks
>
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