On Wed, 4 Feb 2026, [email protected] wrote:
> On Wed, Feb 04, 2026 at 03:37:12PM -0800, Stefano Stabellini wrote:
> > Enable dom0less guests on ARM to use console_io hypercalls:
> > - set input_allow = true for dom0less domains
> > - update the in-code comment in console.c
> > - prioritize the VUART check to retain the same behavior as today
> >
> > Signed-off-by: Stefano Stabellini <[email protected]>
>
> The code looks good, just one remark wrt prioritizing VUART check.
>
> > ---
> > xen/common/device-tree/dom0less-build.c | 2 ++
> > xen/drivers/char/console.c | 16 ++++++++++------
> > 2 files changed, 12 insertions(+), 6 deletions(-)
> >
> > diff --git a/xen/common/device-tree/dom0less-build.c
> > b/xen/common/device-tree/dom0less-build.c
> > index 840d14419d..cb7026fa7e 100644
> > --- a/xen/common/device-tree/dom0less-build.c
> > +++ b/xen/common/device-tree/dom0less-build.c
> > @@ -829,6 +829,8 @@ static int __init construct_domU(struct kernel_info
> > *kinfo,
> >
> > rangeset_destroy(kinfo->xen_reg_assigned);
> >
> > + d->console->input_allowed = true;
> > +
> > return rc;
> > }
> >
> > diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
> > index d3ce925131..7f0c3d8376 100644
> > --- a/xen/drivers/char/console.c
> > +++ b/xen/drivers/char/console.c
> > @@ -610,11 +610,20 @@ static void __serial_rx(char c)
> > if ( ACCESS_ONCE(console_rx) == 0 )
> > return handle_keypress(c, false);
> >
> > + /* Includes an is_focus_domain() check. */
> > d = console_get_domain();
> > if ( !d )
> > return;
> >
> > - if ( is_hardware_domain(d) )
>
> Hardware domain on x86 may have an emulated UART (not in upstream, through,
> I need to send v8 for NS16550 series...). The patch which illustrates the
> idea:
> https://lore.kernel.org/xen-devel/[email protected]/
>
> So this code (hopefully soon) will need adjustment again.
>
> I would update the code to something like:
>
>
>
> if ( is_hardware_domain(d) && !domain_has_vuart(d) )
> {
> // handle hardware domain
> }
> #ifdef CONFIG_SBSA_VUART_CONSOLE
> else if ( domain_has_vuart(d) )
> /* Deliver input to the emulated UART. */
> rc = vpl011_rx_char_xen(d, c);
> #endif
>
>
>
> But domain_has_vuart() needs to be defined for all architectures
> (currently it is hidden in arch/arm/vuart.c).
>
> Or perhaps it is possible to postpone the change?
This change is needed to avoid regressions on ARM.
However, while I wouldn't be surprised if we need a change here for your
upcoming patch series, at the same time at the moment I don't see why
this check wouldn't work as it is for you as well.
On x86, CONFIG_SBSA_VUART_CONSOLE will never be set. It is OK to do this
first:
#ifdef CONFIG_SBSA_VUART_CONSOLE
/* Prioritize vpl011 if enabled for this domain */
if ( d->arch.vpl011.base_addr )
{
/* Deliver input to the emulated UART. */
rc = vpl011_rx_char_xen(d, c);
}
else
#endif
It shouldn't hurt. The is_hardware_domain() check is also not necessary
anymore because any necessary check would be part of this check above:
d = console_get_domain();
if ( !d )
return;
So I am guessing that your series might actually leave this code
unchanged and instead might modify console_get_domain() or
max_console_rx.
> > +#ifdef CONFIG_SBSA_VUART_CONSOLE
> > + /* Prioritize vpl011 if enabled for this domain */
> > + if ( d->arch.vpl011.base_addr )
> > + {
> > + /* Deliver input to the emulated UART. */
> > + rc = vpl011_rx_char_xen(d, c);
> > + }
> > + else
> > +#endif
> > {
> > unsigned long flags;
> >
> > @@ -633,11 +642,6 @@ static void __serial_rx(char c)
> > */
> > send_guest_domain_virq(d, VIRQ_CONSOLE);
> > }
> > -#ifdef CONFIG_SBSA_VUART_CONSOLE
> > - else
> > - /* Deliver input to the emulated UART. */
> > - rc = vpl011_rx_char_xen(d, c);
> > -#endif
> >
> > if ( consoled_is_enabled() )
> > /* Deliver input to the PV shim console. */
> > --
> > 2.25.1
> >
> >
>
