On Fri, May 10, 2019 at 02:41:36PM +0800, Hou Qiming wrote: > > Only allow one resolution change per guest boot, which prevents a > > > > crash when the guest writes garbage to the configuration space (e.g. > > > when rebooting). > > > > Hmm? Did you see that happen in practice? > > It is not easy to write to fw_cfg by accident ... > > > > > Yes, this does happen in practice. It's observed in KVMGT setups by another > github user and me, when the guest Intel driver loads or when the guest > reboots. Link: > https://github.com/intel/gvt-linux/issues/23#issuecomment-483651476 > > Now that you mentioned it, I start to feel that it's not accidental. A > closer look at the "garbage" in that post shows that the overwriting > content are valid resolution values in the wrong endian. It could be a > misguided attempt to "resize ramfb" by the guest Intel driver.
Hmm. The intel driver certainly isn't supposed to do that ... So, allow writing only once might be a good idea, to make clear this *really* is meant to be used by the firmware only, for a boot display. cheers, Gerd
