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

[Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>]

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;
>>         else
>>                 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?

> 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()

-- 
Ard.

>>   }
>>
>>   static int __init xen_guest_init(void)
>>
>
> Regards,
>
> --
> Julien Grall

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