Re: [RESEND][PATCH v2 5/7] xen: include xen/guest_access.h rather than asm/guest_access.h

[Julien Grall <julien@xen.org>]

On 18/08/2020 09:50, Jan Beulich wrote:
> On 14.08.2020 21:07, Julien Grall wrote:
>> Hi Jan,
>>
>> On 31/07/2020 12:36, Jan Beulich wrote:
>>> On 30.07.2020 20:18, Julien Grall wrote:
>>>> From: Julien Grall <jgrall@amazon.com>
>>>>
>>>> Only a few places are actually including asm/guest_access.h. While this
>>>> is fine today, a follow-up patch will want to move most of the helpers
>>>> from asm/guest_access.h to xen/guest_access.h.
>>>>
>>>> To prepare the move, everyone should include xen/guest_access.h rather
>>>> than asm/guest_access.h.
>>>>
>>>> Interestingly, asm-arm/guest_access.h includes xen/guest_access.h. The
>>>> inclusion is now removed as no-one but the latter should include the
>>>> former.
>>>>
>>>> Signed-off-by: Julien Grall <jgrall@amazon.com>
>>>
>>> Acked-by: Jan Beulich <jbeulich@suse.com>
>>>
>>> Is there any chance you could take measures to avoid new inclusions
>>> of asm/guest_access.h to appear?
>>
>> It should be possible.
>>
>> How about this:
>>
>> diff --git a/xen/include/asm-arm/guest_access.h b/xen/include/asm-arm/guest_access.h
>> index b9a89c495527..d8dbc7c973b4 100644
>> --- a/xen/include/asm-arm/guest_access.h
>> +++ b/xen/include/asm-arm/guest_access.h
>> @@ -1,3 +1,7 @@
>> +#ifndef ALLOW_INCLUDE_ASM_GUEST_ACCESS_H
>> +#error "asm/guest_access.h should not be included directly"
>> +#endif
>> +
>>   #ifndef __ASM_ARM_GUEST_ACCESS_H__
>>   #define __ASM_ARM_GUEST_ACCESS_H__
>>
>> diff --git a/xen/include/asm-x86/guest_access.h b/xen/include/asm-x86/guest_access.h
>> index 369676f31ac3..e665ca3a27af 100644
>> --- a/xen/include/asm-x86/guest_access.h
>> +++ b/xen/include/asm-x86/guest_access.h
>> @@ -4,6 +4,10 @@
>>    * Copyright (c) 2006, K A Fraser
>>    */
>>
>> +#ifndef ALLOW_INCLUDE_ASM_GUEST_ACCESS_H
>> +#error "asm/guest_access.h should not be included directly"
>> +#endif
>> +
>>   #ifndef __ASM_X86_GUEST_ACCESS_H__
>>   #define __ASM_X86_GUEST_ACCESS_H__
>>
>> diff --git a/xen/include/xen/guest_access.h b/xen/include/xen/guest_access.h
>> index 75103d30c8be..814e31329de9 100644
>> --- a/xen/include/xen/guest_access.h
>> +++ b/xen/include/xen/guest_access.h
>> @@ -7,7 +7,9 @@
>>   #ifndef __XEN_GUEST_ACCESS_H__
>>   #define __XEN_GUEST_ACCESS_H__
>>
>> +#define ALLOW_INCLUDE_ASM_GUEST_ACCESS_H
>>   #include <asm/guest_access.h>
>> +#undef ALLOW_INCLUDE_ASM_GUEST_ACCESS_H
>>   #include <xen/types.h>
>>   #include <public/xen.h>
> 
> One option. Personally I'd prefer to avoid introduction of yet another
> constant, by leveraging __XEN_GUEST_ACCESS_H__ instead.

I thought about it but it doesn't prevent new inclusions of 
asm/guest_access.h. For instance, the following would still compile:

#include <xen/guest_access.h>

[...]

#include <asm/guest_access.h>

If we want to completely prevent new inclusion, then we need a new 
temporary constant.

Cheers,

-- 
Julien Grall