Re: [PATCH v2 1/4] docs: add xen_ulong_t to the documented integers sizes/alignments

[Julien Grall <julien.grall.oss@xxxxxxxxx>]

On Fri, 12 Apr 2024 at 11:30, Bertrand Marquis <Bertrand.Marquis@xxxxxxx> wrote:

Hi Julien,

> On 12 Apr 2024, at 15:53, Julien Grall <julien.grall.oss@xxxxxxxxx> wrote:
>
>
>
> On Thu, 11 Apr 2024 at 18:08, Stefano Stabellini <sstabellini@xxxxxxxxxx> wrote:
> On Wed, 10 Apr 2024, Julien Grall wrote:
> > On Wed, 10 Apr 2024 at 19:47, Stefano Stabellini <stefano.stabellini@xxxxxxx> wrote:
> >       xen_ulong_t is widely used in public headers.
> >
> >       Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx>
> >       ---
> >
> >       Given that xen_ulong_t is used in public headers there could be a better
> >       place for documenting it but this was the most straightforward to add.
> >       ---
> >        docs/misra/C-language-toolchain.rst | 11 +++++++++++
> >        1 file changed, 11 insertions(+)
> >
> >       diff --git a/docs/misra/C-language-toolchain.rst b/docs/misra/C-language-toolchain.rst
> >       index 5ddfe7bdbe..7a334260e6 100644
> >       --- a/docs/misra/C-language-toolchain.rst
> >       +++ b/docs/misra/C-language-toolchain.rst
> >       @@ -531,6 +531,17 @@ A summary table of data types, sizes and alignment is below:
> >             - 64 bits
> >             - x86_64, ARMv8-A AArch64, RV64, PPC64
> >
> >       +   * - xen_ulong_t
> >       +     - 32 bits
> >       +     - 32 bits
> >       +     - x86_32
> >       +
> >       +   * - xen_ulong_t
> >       +     - 64 bits
> >       +     - 64 bits
> >       +     - x86_64, ARMv8-A AArch64, RV64, PPC64, ARMv8-A AArch32, ARMv8-R
> >       +       AArch32, ARMv7-A
> >
> >
> > We support neither ARMv8-R nor ARMv8-A Aarch32.
> >
> > I could possibly accept the latter because it works to. But the former is so far misleading.
>
> Yes I think you are right. Moreover this document
> (C-language-toolchain.rst) is meant for the Xen build. While this patch
> is trying to document the types used in the public headers for the
> external-facing ABI.
>
> I'll move the information this patch is adding to a separate document,
> specific to the public headers. I will only add the architectures
> currently working: I'll add ARMv8-A Aarch32 because although it is
> unsupported it is interesting to know the size of xen_ulong_t for
> aarch32 in the public headers. I will remove ARMv8-R as it is not
> available upstream.
>
> Thinking a bit more. What about Armv9? Rather than listing each version, should we instead use ARMv7-A aarch32 and later, ARMv8-A aarch64 and later?

Definitely you are right here but as for Armv8-R, Armv9 is not something that we explicitely support right now (even though it should work).

I am confused with the comparison. I thought you can’t boot Xen at all on Armv8-R. But you can on Armv9-A as this just Armv8-A + features the software don’t need to use.

Did you intend to draw the comparison with Armv8-A Aarch32?

Cheers,

Cheers
Bertrand