On Sat, 2019-02-09 at 19:44 -0500, Michael S. Tsirkin wrote: > On Mon, Feb 04, 2019 at 10:15:46AM -0800, Alexander Duyck wrote: > > From: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx> > > > > Add the host side of the KVM memory hinting support. With this we expose a > > feature bit indicating that the host will pass the messages along to the > > new madvise function. > > > > This functionality is mutually exclusive with device assignment. If a > > device is assigned we will disable the functionality as it could lead to a > > potential memory corruption if a device writes to a page after KVM has > > flagged it as not being used. > > I really dislike this kind of tie-in. > > Yes right now assignment is not smart enough but generally > you can protect the unused page in the IOMMU and that's it, > it's safe. > > So the policy should not leak into host/guest interface. > Instead it is better to just keep the pages pinned and > ignore the hint for now. Okay, I can do that. It also gives me a means of benchmarking just the hypercall cost versus the extra page faults and zeroing.
