Re: [PATCH for-8.2 1/3] vl: revert behaviour for -display none

[Peter Maydell]

On Fri, 17 Nov 2023 at 14:35, <marcandre.lureau@redhat.com> wrote:
>
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
>
> Commit 1bec1cc0d ("ui/console: allow to override the default VC") changed
> the behaviour of the "-display none" option, so that it now creates a
> QEMU monitor on the terminal. "-display none" should not be tangled up
> with whether we create a monitor or a serial terminal; it should purely
> and only disable the graphical window. Changing its behaviour like this
> breaks command lines which, for example, use semihosting for their
> output and don't want a graphical window, as they now get a monitor they
> never asked for.
>
> It also breaks the command line we document for Xen in
> docs/system/i386/xen.html:
>
>  $ ./qemu-system-x86_64 --accel kvm,xen-version=0x40011,kernel-irqchip=split \
>     -display none -chardev stdio,mux=on,id=char0,signal=off -mon char0 \
>     -device xen-console,chardev=char0  -drive file=${GUEST_IMAGE},if=xen
>
> qemu-system-x86_64: cannot use stdio by multiple character devices
> qemu-system-x86_64: could not connect serial device to character backend
> 'stdio'
>
> When qemu is compiled without PIXMAN, by default the serials aren't
> muxed with the monitor anymore on stdio. The serials are redirected to
> "null" instead, and the monitor isn't set up.
>
> Fixes: commit 1bec1cc0d ("ui/console: allow to override the default VC")
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>  system/vl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/system/vl.c b/system/vl.c
> index 5af7ced2a1..14bf0cf0bf 100644
> --- a/system/vl.c
> +++ b/system/vl.c
> @@ -1391,7 +1391,7 @@ static void qemu_create_default_devices(void)
>          }
>      }
>
> -    if (nographic || (!vc && !is_daemonized() && isatty(STDOUT_FILENO))) {
> +    if (nographic) {
>          if (default_parallel) {
>              add_device_config(DEV_PARALLEL, "null");
>          }

This fixes the regression I was seeing with the semihosting
use case. I haven't checked the Xen setup.

Tested-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM