[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [Draft F] Xen on ARM vITS Handling
On Thu, 2015-06-11 at 10:40 +0100, Ian Campbell wrote: > ## Command Queue Virtualisation > > The command translation/emulation in this design has been arranged to > be as cheap as possible (e.g. in many cases the actions are NOPs), > avoiding previous concerns about the length of time which an emulated > write to a `CWRITER` register may block the vcpu. > > The vits will simply track its reader and writer pointers. On write > to `CWRITER` it will immediately and synchronously process all > commands in the queue and update its state accordingly. > > It might be possible to implement a rudimentary form of preemption by > periodically (as determined by `hypercall_preempt_check()`) returning > to the guest without incrementing PC but with updated internal > `CREADR` state, meaning it will reexecute the write to `CWRITER` and > we can pickup where we left off for another iteration. This at least > lets us schedule other vcpus etc and prevents a monopoly. In the presence of multiple VCPUs writing to GITS_CWRITER preemption actually gets pretty subtle. I suggest leaving it out for now. Ian. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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