On Mon, Jun 15, 2020 at 04:33:33PM +0100, Andrew Cooper wrote: > On 12/06/2020 16:56, Roger Pau Monne wrote: > > Some video BIOS require a PIT in order to work properly, hence classic > > PV dom0 gets partial access to the physical PIT as long as it's not in > > use by Xen. > > Is this actually true today?
TBH I have no idea and asked the same thing myself. > I can believe that it may have been necessary on old hardware, but the > structure of systems has changed massively over the past 20 years, and > the PIT is very legacy these days. I also wondered whether video BIOSes really changed in the last 20 years, I really have no idea. FWIW, Wikipedia still lists PIT as being used by video BIOSes on x86 systems [0] but there are no references to specific models or video BIOSes. Alternatively we could add this as a Xen command line option, ie: dom0=pit or some such. It's however not very nice to not get output because the video BIOS doesn't function properly due to lack of PIT. Thanks, Roger. [0] https://en.wikipedia.org/wiki/Intel_8253#IBM_PC_programming_tips_and_hints
