Re: [RFC PATCH 1/3] arch, arm32: add definition of paddr_bits

[Julien Grall <julien.grall@linaro.org>]

Hello Arianna,

On 02/03/14 08:49, Arianna Avanzini wrote:
> Currently, the paddr_bits variable, which keeps the machine word size,
> is not defined for the arm32 architecture. This commits adds its
> definition for arm32 in a new header in the architecture-specific
> directory.
> This change is instrumental to the implementation of the
> XEN_DOMCTL_memory_mapping hypercall, added in the following
> commit.

paddr_bits doesn't keep the machine word size but the size of the 
physical address.

On ARM, this value is fixed and defined as PADDR_BITS in
xen/include/asm-arm/page.h. I don't think we need to introduce a 
variable for this purpose. x86 defines paddr_bits because the value can 
change on some processor.

> diff --git a/xen/arch/arm/arm32/cpu.h b/xen/arch/arm/arm32/cpu.h
> new file mode 100644
> index 0000000..1091051
> --- /dev/null
> +++ b/xen/arch/arm/arm32/cpu.h
> @@ -0,0 +1,7 @@
> +#ifndef __ARM_ARM32_CPU_H
> +#define __ARM_ARM32_CPU_H
> +
> +/* ARM-v7 features LPAE (machine word size is 40 bit) */
> +unsigned int paddr_bits = 40;
> +

Global variable must not be defined in headers. If someone decides to 
include this header in 2 differents C files, the variable will be 
defined twice. Therefore the linker-step will fail.

You should define it in a c-file.

Regards,

-- 
Julien Grall