Re: [XEN PATCH] xen: cache clearing and invalidation helpers refactoring

[Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>]

On 2024-02-26 11:51, Jan Beulich wrote:
> On 23.02.2024 08:58, Nicola Vetrini wrote:
> > On 2024-02-19 16:14, Nicola Vetrini wrote:
> > > The cache clearing and invalidation helpers in x86 and Arm didn't
> > > comply with MISRA C Rule 17.7: "The value returned by a function
> > > having non-void return type shall be used". On Arm they
> > > were always returning 0, while some in x86 returned -EOPNOTSUPP
> > > and in common/grant_table the return value is saved.
> > >
> > > As a consequence, a common helper arch_grant_cache_flush that returns
> > > an integer is introduced, so that each architecture can choose 
> > > whether
> > > to
> > > return an error value on certain conditions, and the helpers have
> > > either
> > > been changed to return void (on Arm) or deleted entirely (on x86).
> > >
> > > Signed-off-by: Julien Grall <julien@xxxxxxx>
> > > Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
> > > ---
> > > The original refactor idea came from Julien Grall in [1]; I edited 
> > > that
> > > proposal
> > > to fix build errors.
> > >
> > > I did introduce a cast to void for the call to flush_area_local on 
> > > x86,
> > > because
> > > even before this patch the return value of that function wasn't 
> > > checked
> > > in all
> > > but one use in x86/smp.c, and in this context the helper (perhaps
> > > incidentally)
> > > ignored the return value of flush_area_local.
> > >
> > > [1]
> > > https://lore.kernel.org/xen-devel/09589e8f-77b6-47f7-b5bd-cf485e4b60f1@xxxxxxx/
> > > ---
> > >  xen/arch/arm/include/asm/page.h     | 33 
> > > ++++++++++++++++++-----------
> > >  xen/arch/x86/include/asm/flushtlb.h | 23 ++++++++++----------
> > >  xen/common/grant_table.c            |  9 +-------
> > >  3 files changed, 34 insertions(+), 31 deletions(-)
> > I'll put this patch in the backlog at the moment: too many intricacies
> > while trying to untangle xen/flushtlb from xen/mm.h, and there are
> > easier cases that can be done faster. If someone is interested I can
> > post the partial work I've done so far, even though it doesn't
> > build on x86.
> This
> https://lists.xen.org/archives/html/xen-devel/2024-02/msg01513.html
> may be of interest to you in the context here.
I'll take a look, thanks.

--
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)