On Thu, Oct 02, 2025 at 11:37:36AM +0100, Andrew Cooper wrote: > On 02/10/2025 11:22 am, Roger Pau Monne wrote: > > Reading from the E9 port if the emergency console is active should return > > 0xe9 according to the documentation from Bochs: > > > > https://bochs.sourceforge.io/doc/docbook/user/bochsrc.html > > > > See `port_e9_hack` section description. > > > > Fix Xen so it also returns the port address. OSes can use it to detect > > whether the emergency console is available or not. > > > > Fixes: d1bd157fbc9b ("Big merge the HVM full-virtualisation abstractions.") > > Signed-off-by: Roger Pau Monné <[email protected]> > > Reviewed-by: Andrew Cooper <[email protected]> > > That's been wrong for rather a long time. How did you find it?
I came across the documentation above and I didn't remember Xen returning any value for reads, which sadly was indeed true. This was because I had the intention to suggest Alejandro to (also?) use the port 0xe9 hack for printing from XTF, which should work for both Xen and QEMU. > CC-ing Oleksii as you've tagged this for 4.21. I was told that bugfixes didn't need a release-ack until hard code freeze, which is the 31st of October? Thanks, Roger.
