On Wed, Nov 22, 2017 at 8:05 PM, Xiao Guangrong <xiaoguangrong.eric@xxxxxxxxx> wrote: > > > On 11/22/2017 02:19 AM, Rik van Riel wrote: > >> We can go with the "best" interface for what >> could be a relatively slow flush (fsync on a >> file on ssd/disk on the host), which requires >> that the flushing task wait on completion >> asynchronously. > > > I'd like to clarify the interface of "wait on completion > asynchronously" and KVM async page fault a bit more. > > Current design of async-page-fault only works on RAM rather > than MMIO, i.e, if the page fault caused by accessing the > device memory of a emulated device, it needs to go to > userspace (QEMU) which emulates the operation in vCPU's > thread. > > As i mentioned before the memory region used for vNVDIMM > flush interface should be MMIO and consider its support > on other hypervisors, so we do better push this async > mechanism into the flush interface design itself rather > than depends on kvm async-page-fault. I would expect this interface to be virtio-ring based to queue flush requests asynchronously to the host.
