Re: [XEN PATCH v2] arm64/vfp: address MISRA C:2012 Dir 4.3

[Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>]

On 24/08/2023 10:01, Michal Orzel wrote:
> Hi Nicola,
>
> On 24/08/2023 09:37, Nicola Vetrini wrote:
> > Directive 4.3 prescribes the following:
> > "Assembly language shall be encapsulated and isolated",
> > on the grounds of improved readability and ease of maintenance.
> >
> > A static inline function is the chosen encapsulation mechanism.
> >
> > No functional change.
> >
> > Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
> > ---
> > Changes in v2:
> > - Switched to a static inline function
> > ---
> >  xen/arch/arm/arm64/vfp.c | 78 
> > ++++++++++++++++++++++------------------
> >  1 file changed, 44 insertions(+), 34 deletions(-)
> >
> > diff --git a/xen/arch/arm/arm64/vfp.c b/xen/arch/arm/arm64/vfp.c
> > index 2d0d7c2e6ddb..5c884380ee42 100644
> > --- a/xen/arch/arm/arm64/vfp.c
> > +++ b/xen/arch/arm/arm64/vfp.c
> > @@ -4,6 +4,48 @@
> >  #include <asm/vfp.h>
> >  #include <asm/arm64/sve.h>
> >
> > +static inline void save_state(uint64_t *fpregs)
> > +{
> > +    asm volatile("stp q0, q1, [%1, #16 * 0]\n\t"
> > +                 "stp q2, q3, [%1, #16 * 2]\n\t"
> > +                 "stp q4, q5, [%1, #16 * 4]\n\t"
> > +                 "stp q6, q7, [%1, #16 * 6]\n\t"
> > +                 "stp q8, q9, [%1, #16 * 8]\n\t"
> > +                 "stp q10, q11, [%1, #16 * 10]\n\t"
> > +                 "stp q12, q13, [%1, #16 * 12]\n\t"
> > +                 "stp q14, q15, [%1, #16 * 14]\n\t"
> > +                 "stp q16, q17, [%1, #16 * 16]\n\t"
> > +                 "stp q18, q19, [%1, #16 * 18]\n\t"
> > +                 "stp q20, q21, [%1, #16 * 20]\n\t"
> > +                 "stp q22, q23, [%1, #16 * 22]\n\t"
> > +                 "stp q24, q25, [%1, #16 * 24]\n\t"
> > +                 "stp q26, q27, [%1, #16 * 26]\n\t"
> > +                 "stp q28, q29, [%1, #16 * 28]\n\t"
> > +                 "stp q30, q31, [%1, #16 * 30]\n\t"
> > +                 : "=Q" (*fpregs) : "r" (fpregs));
> > +}
> > +
> > +static inline void restore_state(uint64_t *fpregs)
> This can be const as you are loading data from fpregs into registers
I wonder whether this would make a difference, given that the return 
type is void.
It's fine either way, tough.

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