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Re: [Xen-devel] [PATCH v2] xen/arm: allow console=hvc0 to be omitted for guests

On 13/02/2015 15:12, Ard Biesheuvel wrote:
On 13 February 2015 at 15:03, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
Hi Ard,

On 12/02/2015 19:29, Ard Biesheuvel wrote:

This patch registers hvc0 as the preferred console if no console
has been specified explicitly on the kernel command line.

The purpose is to allow platform agnostic kernels and boot images
(such as distro installers) to boot in a Xen/ARM domU without the
need to modify the command line by hand.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
   arch/arm/xen/enlighten.c | 4 ++++
   1 file changed, 4 insertions(+)

diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index 0abeefa7dbf8..927be1d1bad7 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -24,6 +24,7 @@
   #include <linux/cpuidle.h>
   #include <linux/cpufreq.h>
   #include <linux/cpu.h>
+#include <linux/console.h>

   #include <linux/mm.h>

@@ -255,6 +256,9 @@ void __init xen_early_init(void)
                 xen_start_info->flags |= SIF_INITDOMAIN|SIF_PRIVILEGED;
                 xen_start_info->flags &= ~(SIF_INITDOMAIN|SIF_PRIVILEGED);
+       if (!console_set_on_cmdline && !xen_initial_domain())
+               add_preferred_console("hvc", 0, NULL);

Unfortunately, this won't work as expected.

Did you try it?

No just looked at the code.

console_set_on_cmdline is set when Linux parses the early params. The
parsing is done after setup_arch (the function which call xen_early_init).

So we will end up to add the HVC console even if a console has been passed
on the command line.

parse_early_param() is also called by setup_arch(), before xen_early_init()

The call to parse_early_param() in generic code is only there for
architectures that don't call it in their setup_arch()

Oh, right. Sorry for the noise.


Reviewed-by: Julien Grall <julien.grall@xxxxxxxxxx>


Julien Grall

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