Am 04.02.2015 um 11:39 schrieb Paolo Bonzini: >> Conny: >> I am asking myself, if we should explicitly add a comment in the >> virtio-ccw spec, that all accesses are assumed to be with key 0 and >> thus never cause key protection. The change/reference bit is set >> by the underlying I/O or memory copy anyway. > > Can you explain the last sentence? :)
Whenever vhost or qemu or a finished aio request wrote content into a virtio buffer, the HW has set the storage key for that physical page, which makes it automatically dirty/referenced in the guest visible storage key. For completeness sake: Now, if the guest does not use the storage key, but instead the new fault based software dirty tracking, it wont notice the change bit. The guest I/O itself when finished will mark the struct page as Dirty, just like on x86. Makes sense? Christian
