Re: [RFC PATCH] libacpi: Fix cross building x86 on arm

[Jan Beulich <jbeulich@xxxxxxxx>]

On 23.08.2022 15:34, Bertrand Marquis wrote:
>> On 23 Aug 2022, at 13:33, Jan Beulich <jbeulich@xxxxxxxx> wrote:
>> On 23.08.2022 12:24, Bertrand Marquis wrote:
>>> --- a/tools/libacpi/mk_dsdt.c
>>> +++ b/tools/libacpi/mk_dsdt.c
>>> @@ -18,6 +18,16 @@
>>> #include <stdlib.h>
>>> #include <stdbool.h>
>>> #if defined(CONFIG_X86)
>>> +/*
>>> + * When building on non x86 host, arch-x86/xen.h will include xen.h which 
>>> will
>>> + * try to include the arch xen.h (for example if built on arm, x86/xen.h 
>>> will
>>> + * include xen.h which will include arch-arm.h).
>>> + * To prevent this effect, define x86 to have the proper sub arch included 
>>> when
>>> + * the compiler does not define it.
>>> + */
>>> +#if !(defined(__i386__) || defined(__x86_64__))
>>> +#define __x86_64__
>>> +#endif
>>
>> Besides being confusing this depends on the order of checks in xen.h.
>>
>>> #include <xen/arch-x86/xen.h>
>>> #include <xen/hvm/hvm_info_table.h>
>>> #elif defined(CONFIG_ARM_64)
>>
>> At the very least you will want to #undef the auxiliary define as soon
>> as practically possible.
> 
> Ack
> 
>>
>> But I think a different solution will want finding. Did you check what
>> the #include is needed for, really? I've glanced through the file
>> without being able to spot anything ... After all this is a build tool,
>> which generally can't correctly use many of the things declared in the
>> header.
> 
> As stated in the comment after the commit message, this is not a good
> solution but an hack.
> 
> Now I do not completely agree here, the tool is not really the problem
> but the headers are.

Well - the issue is the tool depending on these headers.

> There is not such an issue on arm.

Then why does the tool include xen/arch-arm.h for Arm64?

> The tool needs at least:
> HVM_MAX_VCPUS
> XEN_ACPI_CPU_MAP
> XEN_ACPI_CPU_MAP_LEN
> XEN_ACPI_GPE0_CPUHP_BIT
> 
> Which are defined in arch-x86/xen.h and hvm_info_table.h.
> 
> I am not quite sure how to get those without the current include

1) Move those #define-s to a standalone header, which the ones
currently defining them would simply include. The tool would then
include _only_ this one header.

2) Seddery on the headers, producing a local one to be used by the
tool.

Jan