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



Hi Jan,

On 21/01/2021 10:24, Jan Beulich wrote:
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.

Do you have a suggestion how the "choice" can appear in the .config?

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

The base address doesn't need to be page-aligned (some HW have multiple UARTs in the same 4K region).

Cheers,

--
Julien Grall



 


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