Messages in this thread | | | Subject | Re: [RFC PATCH 10/24] vdpa: introduce config operations for associating ASID to a virtqueue group | From | Jason Wang <> | Date | Mon, 12 Oct 2020 15:45:10 +0800 |
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On 2020/10/12 下午2:59, Eli Cohen wrote: > On Fri, Oct 09, 2020 at 11:56:45AM +0800, Jason Wang wrote: >> On 2020/10/1 下午9:29, Eli Cohen wrote: >>> On Thu, Sep 24, 2020 at 11:21:11AM +0800, Jason Wang wrote: >>>> This patch introduces a new bus operation to allow the vDPA bus driver >>>> to associate an ASID to a virtqueue group. >>>> >>> So in case of virtio_net, I would expect that all the data virtqueues >>> will be associated with the same address space identifier. >> >> Right. >> >> I will add the codes to do this in the next version. It should be more >> explicit than have this assumption by default. >> >> >>> Moreover, >>> this assignment should be provided before the set_map call that provides >>> the iotlb for the address space, correct? >> >> I think it's better not have this limitation, note that set_map() now takes >> a asid argument. >> >> So for hardware if the associated as is changed, the driver needs to program >> the hardware to switch to the new mapping. >> >> Does this work for mlx5? >> > So in theory we can have several asid's (for different virtqueues), each > one should be followed by a specific set_map call. If this is so, how do > I know if I met all the conditions run my driver? Maybe we need another > callback to let the driver know it should not expect more set_maps().
This should work similarly as in the past. Two parts of the work is expected to be done by the driver:
1) store the mapping somewhere (e.g hardware) during set_map() 2) associating mapping with a specific virtqueue
The only difference is that more than one mapping is used now.
For the issue of more set_maps(), driver should be always ready for the new set_maps() call instead of not expecting new set_maps() since guest memory topology could be changed due to several reasons.
Qemu or vhost-vDPA will try their best to avoid the frequency of set_maps() for better performance (e.g through batched IOTLB updating). E.g there should be at most one set_map() during one time of guest booting.
Thanks
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