On Thu, Feb 04, 2010 at 09:16:47PM +0200, Avi Kivity wrote: > On 01/28/2010 09:03 PM, Marcelo Tosatti wrote: > >A vcpu can be stopped after handling IO in userspace, > >but before returning to kernel to finish processing. > > > > Is this strictly needed? If we teach qemu to migrate before > executing the pio request, I think we'll be all right? should work > at least for IN/INS, not sure about OUT/OUTS.
It would be nice (instead of more state to keep track of between kernel/user) but the drawbacks i see are: You'd have to add a limitation so that any IN which was processed by device emulation has to re-entry kernel to complete it (so it complicates vcpu stop in userspace). And for OUTS larger than page size (== arch->pio_data size) you need to know the current position to continue it on the destination (or roll back the entire effect of the instruction in device emulation, and RIP). -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
