Re: [PATCH] generic/altp2m: address violations of MISRA C Rule 2.1

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 9 Apr 2026, Dmytro Prokopchuk1 wrote:
> MISRA C Rule 2.1 states: "A project shall not contain unreachable code".
> 
> In certain build configurations, the function 'altp2m_vcpu_idx()' is defined
> as an inline function that contains the 'BUG()' macro. This resulted in a
> violation because the 'BUG()' macro makes the function non-returning.
> 
> To ensure compliance with MISRA C Rule 2.1, this patch removes the inline
> function implementation and its BUG()-based unreachable code. It is replaced
> with an unconditional function declaration for 'altp2m_vcpu_idx()'. It relies
> on the compiler's Dead Code Elimination (DCE) to remove the unused function
> in builds where it is not needed.
> 
> Signed-off-by: Dmytro Prokopchuk <dmytro_prokopchuk1@xxxxxxxx>
> ---
> Test CI pipeline:
> https://gitlab.com/xen-project/people/dimaprkp4k/xen/-/pipelines/2441424553
> ---
>  xen/include/asm-generic/altp2m.h | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/xen/include/asm-generic/altp2m.h 
> b/xen/include/asm-generic/altp2m.h
> index 39865a842a..df6b9a9c01 100644
> --- a/xen/include/asm-generic/altp2m.h
> +++ b/xen/include/asm-generic/altp2m.h
> @@ -15,12 +15,7 @@ static inline bool altp2m_active(const struct domain *d)
>  }
>  
>  /* Alternate p2m VCPU */
> -static inline unsigned int altp2m_vcpu_idx(const struct vcpu *v)
> -{
> -    /* Not implemented on GENERIC, should not be reached. */
> -    BUG();
> -    return 0;
> -}
> +uint16_t altp2m_vcpu_idx(const struct vcpu *v);

The return type being changed to uint16_t is also a fix. It should be
mentioned in the commit message. Aside from that:

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


>  #endif /* __ASM_GENERIC_ALTP2M_H */
>  
> -- 
> 2.43.0
>