Re: [PATCH v2 2/2] xen/console: unify printout behavior for UART emulators

[Jan Beulich <jbeulich@xxxxxxxx>]

On 05.06.2025 02:46, dmkhn@xxxxxxxxx wrote:
> From: Denis Mukhin <dmukhin@xxxxxxxx>
> 
> If virtual UART from domain X prints on the physical console, the behavior is
> updated to (see [1]):
> - console focus in domain X: do not prefix messages;
> - no console focus in domain X: prefix all messages with "(dX)".
> 
> Use guest_printk() without rate-limiting in all current in-hypervisor UART
> emulators. That aligns the behavior with debug I/O port 0xe9 handler on x86 
> and
> slightly improves the logging since guest_printk() already prints the domain
> ID. guest_printk() was modified to account for console focus ownership.
> 
> Modify guest_console_write() for hardware domain case by adding domain ID to
> the message when hwdom does not have console focus.
> 
> [1] 
> https://lore.kernel.org/xen-devel/alpine.DEB.2.22.394.2412121655360.463523@ubuntu-linux-20-04-desktop/
> Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
> ---
> Changes since v1:
> - dropped change for debug port and for HYPERVISOR_console_io hypercall

Yet then what about ...

> --- a/xen/arch/arm/vuart.c
> +++ b/xen/arch/arm/vuart.c
> @@ -89,7 +89,7 @@ static void vuart_print_char(struct vcpu *v, char c)
>          if ( c != '\n' )
>              uart->buf[uart->idx++] = '\n';
>          uart->buf[uart->idx] = '\0';
> -        printk(XENLOG_G_DEBUG "DOM%u: %s", d->domain_id, uart->buf);
> +        guest_printk(d, "%s", uart->buf);
>          uart->idx = 0;
>      }
>      spin_unlock(&uart->lock);

... this dropping of XENLOG_G_DEBUG? In fact I'd have expected such to
be _added_ where presently missing.

Jan