Re: [PATCH for-4.21] x86/hvm: fix reading from 0xe9 IO port if port E9 hack is active

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

On 10/2/25 3:38 PM, 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 <roger.pau@xxxxxxxxxx>
> > >         
> > Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> >
> > 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?
>     
I meant until the start of the hard code freeze, which is on October 4.
So there is no need for a release-ack for this patch.

Thanks.

~ Oleksii