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

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi Julien,

> On 12 Apr 2024, at 19:01, Julien Grall <julien.grall.oss@xxxxxxxxx> wrote:
> 
> 
> 
> 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?

Yes in my mind armv9 even if currently working it is not something officially 
supported so it is in the same state as armv8 aarch32.

Armv8-R currently cannot work at all so it is a different state.

Cheers
Bertrand

> 
> Cheers,
> 
> 
> 
> Cheers
> Bertrand