Re: [Qemu-devel] [PATCH 08/13] iommu: Introduce IOMMU emulation infrastructure

[Anthony Liguori]

On 05/15/2012 08:20 PM, Benjamin Herrenschmidt wrote:
> On Tue, 2012-05-15 at 19:54 -0500, Anthony Liguori wrote:
> > You certainly could do that but it may get a little weird dealing with the
> > return path.  You'd have to return something like -EWOULDBLOCK and make sure you
> > handle that in the dispatch code appropriately.
>
> Hrm, our implementation of kvm_arch_handle_exit() always return "1"
> after a hypercall, forcing kvm_cpu_exec() to return back to the thread
> loop, so we should be ok to just set env->halted and return no ?

I meant, if you wanted to have a synchronous hypercall function to dispatch, and 
then later call "hypercall_finish()", you would need a way to return an error in 
the synchronous hypercall to identify that something else would eventually call 
"hypercall_finish()."  The sync hypercall would need to return something like 
-EWOULDBLOC.

Setting env->halted=1 ought to be enough to delay returning to the guest 
although i'd have to go through the code to verify.

Regards,

Anthony Liguori

> Cheers,
> Ben.