On Thu Oct 2, 2025 at 3:38 PM CEST, Roger Pau Monné wrote: > 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.
QEMU doesn't support 0xE9 though? Cheers, Alejandro
