On Tue, Feb 19, 2019 at 09:02:52PM +0100, David Hildenbrand wrote: > On 19.02.19 20:58, Michael S. Tsirkin wrote: > > On Tue, Feb 19, 2019 at 10:06:35AM -0800, Alexander Duyck wrote: > >>> I tend to like an asynchronous reporting approach as discussed in this > >>> thread, we would have to see if Nitesh could get it implemented. > >> > >> I agree it would be great if it could work. However I have concerns > >> given that work on this patch set dates back to 2017, major issues > >> such as working around device assignment have yet to be addressed, > > > > BTW for device assignment to work, your idea of sending > > data directly to kvm won't work, will it? > > You need to update userspace so it can update VFIO right? > > Another blocker for assignment is ability to make holes > > an an existing mapping - supported by hardware but > > not by IOMMU drivers. > > I had the exact same thought and then realized that we decided to block > the balloon in user space until we figured out how to handle this properly. > > I wonder if MADV_FREE behaves differently compared to MADV_DONTNEED when > finding pinned pages, but I doubt it. Most probably we'll have to > disable hinting for device assignments as well. OK but let's recognize it as a bug not a feature. -- MST
