Re: [PATCH 3/3] xen/public: arch-arm: All PSR_* defines should be unsigned

From: Jan Beulich <jbeulich@suse.com>
To: Julien Grall <julien@xen.org>
Cc: Julien Grall <jgrall@amazon.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Bertrand Marquis <bertrand.marquis@arm.com>,
	Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCH 3/3] xen/public: arch-arm: All PSR_* defines should be unsigned
Date: Fri, 18 Aug 2023 10:14:30 +0200	[thread overview]
Message-ID: <58ecfdf4-c0ce-be56-8686-d6fcf06f9609@suse.com> (raw)
In-Reply-To: <2b86f83a-6352-4b43-835b-6c56ad8260ba@xen.org>

On 18.08.2023 09:39, Julien Grall wrote:
> On 18/08/2023 07:33, Jan Beulich wrote:
>> As an aside I wonder why they're here: They look like definitions of
>> processor registers, which aren't under our (Xen's) control.
> 
> I agree they are not under Xen's control. However, they are used by the 
> toolstack and IIRC back then they were not available in any other headers.
> 
> Note that they are only available by the tools and the hypervisor (see 
> #ifdef above).

Yes, I did notice that (or else I would have used stronger wording).

>> I ask in
>> part because the presence of such constants may then be taken as
>> justification to add similar things in new ports. Yet such definitions
>> shouldn't be put here.
> 
>  From my understanding we are using the public headers to provide 
> macros/defines that are used by both the toolstack and the hypervisor. 
> If they are not meant to be exposed to the guest, then they will be 
> protected with "#if defined(__XEN__) || defined(__XEN_TOOLS__)".
> 
> I think we are in a similar situation here. So it is not clear where 
> they should be put if we need to share them between the hypervisor and 
> the toolstack.

On x86 we simply arrange for certain hypervisor headers to be re-usable
from the toolstack. See in particular arch/x86/include/asm/x86-*.h. And
of course everything under include/xen/lib/x86/, but those are our own
definitions, not ones meant to solely express relevant hw spec aspects.

Jan