Re: [PATCH] xen/arm: Fix compilation error when early printk is enabled

[Jan Beulich <jbeulich@xxxxxxxx>]

On 21.01.2021 10:56, Julien Grall wrote:
> Hi Jan,
> 
> On 21/01/2021 09:43, Jan Beulich wrote:
>> On 21.01.2021 10:30, Michal Orzel wrote:
>>> Fix compilation error when enabling early printk, introduced
>>> by commit aa4b9d1ee6538b5cbe218d4d3fcdf9548130a063:
>>> ```
>>> debug.S: Assembler messages:
>>> debug.S:31: Error: constant expression expected at operand 2 -- `ldr 
>>> x15,=((0x00400000+(0)*PAGE_SIZE)+(0x1c090000&~PAGE_MASK))`
>>> debug.S:38: Error: constant expression expected at operand 2 -- `ldr 
>>> x15,=((0x00400000+(0)*PAGE_SIZE)+(0x1c090000&~PAGE_MASK))`
>>> ```
>>>
>>> The fix is to include header <xen/page-size.h> which now contains
>>> definitions for page/size/mask etc.
>>>
>>> Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
>>
>> I'm sorry for the breakage, but I wonder how I should have noticed
>> the issue. In all the Arm .config-s I'm routinely building I can't
>> even see ...
>>
>>> --- a/xen/include/asm-arm/early_printk.h
>>> +++ b/xen/include/asm-arm/early_printk.h
>>> @@ -10,6 +10,7 @@
>>>   #ifndef __ARM_EARLY_PRINTK_H__
>>>   #define __ARM_EARLY_PRINTK_H__
>>>   
>>> +#include <xen/page-size.h>
>>>   
>>>   #ifdef CONFIG_EARLY_PRINTK
>>
>> ... a respective Kconfig setting, i.e. it's not like I simply
>> failed to enable it.
> 
> EARLY_PRINTK is defined in arch/arm/Kconfig.debug and is selected when 
> you specify the UART to use.
> 
> Assuming you are only build testing, you could add the following for 
> testing EARLY_PRINTK:
> 
> CONFIG_DEBUG=y
> CONFIG_EARLY_UART_CHOICE_8250=y
> CONFIG_EARLY_UART_8250=y
> CONFIG_EARLY_PRINTK=y
> CONFIG_EARLY_UART_BASE_ADDRESS=
> CONFIG_EARLY_UART_8250_REG_SHIFT=0
> CONFIG_EARLY_PRINTK_INC="debug-8250.inc"

Ah yes, this works, thanks. The "optional" on the choice isn't
very helpful I suppose, because when going from an existing
.config one would neither find a setting presently turned off
in that .config, nor will there be a prompt.

I suppose any page-aligned base address is fine to use for my
build-testing-only purposes?

Jan