On Thu, 15 Mar 2012, Tim Deegan wrote: > At 17:14 +0000 on 15 Mar (1331831693), Stefano Stabellini wrote: > > On Thu, 15 Mar 2012, Julien Grall wrote: > > > When an IOREQ_TYPE_INVALIDATE is sent to QEMU, it invalidates all entry > > > of the map cache even if it's locked. > > > > > > QEMU is not able to know that entry was invalidated, so when an IO > > > access is requested a segfault occured. > > > > The problem here is the long term mappings in QEMU that cannot easily be > > re-created. > > I am not sure whether this can cause any trouble to things like > > xenpaging. > > It causes some trouble to ballooning - a guest might try to return memory > to Xen only to find that Qemu won't let go of it. > > If (as I hope is the case) qemu never has a locked mapping to something > that the guets ought to be ballooning, that's OK.
That should be the case. > If this happens just > because the page was recently a DMA target, then it's not. Only if the DMA is still in progress, in that case it is a bad idea to balloon out that page.
