Re: [PATCH v2] docs/misra: document the expected sizes of integer types

From: Stefano Stabellini <sstabellini@kernel.org>
To: Jan Beulich <jbeulich@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
	andrew.cooper3@citrix.com,  bertrand.marquis@arm.com,
	george.dunlap@citrix.com, julien@xen.org,  michal.orzel@amd.com,
	roger.pau@citrix.com, xen-devel@lists.xenproject.org
Subject: Re: [PATCH v2] docs/misra: document the expected sizes of integer types
Date: Fri, 15 Mar 2024 17:07:50 -0700 (PDT)	[thread overview]
Message-ID: <alpine.DEB.2.22.394.2403151658530.853156@ubuntu-linux-20-04-desktop> (raw)
In-Reply-To: <6a76723e-ba47-40b3-8f33-d68030b14299@suse.com>

On Fri, 15 Mar 2024, Jan Beulich wrote:
> On 14.03.2024 23:17, Stefano Stabellini wrote:
> > Xen makes assumptions about the size of integer types on the various
> > architectures. Document these assumptions.
> 
> My prior reservation wrt exact vs minimum sizes remains.

We have to specify the exact size. In practice the size is predetermined
and exact with all our supported compilers given a architecture.

Most importantly, unfortunately we use non-fixed-size integer types in
C hypercall entry points and public ABIs. In my opinion, that is not
acceptable.

We have two options:

1) we go with this document, and we clarify that even if we specify
  "unsigned int", we actually mean a 32-bit integer

2) we change all our public ABIs and C hypercall entry points to use
   fixed-size types (e.g. s/unsigned int/uint32_t/g)

2) is preferred because it is clearer but it is more work. So I went
with 1). I also thought you would like 1) more.

> Additionally, is it really meaningful to document x86-32 as an
> architecture, when it's been many years that the hypervisor cannot be
> built anymore for that target?

You are right. I should take x86_32 out. I'll do it in the next version.