Re: [PATCH 08/14] Arm/guestcopy: deviate copy_guest() uses just like their x86 counterparts

[Nicola Vetrini <nicola.vetrini@bugseng.com>]

On 2026-09-02 08:33, Jan Beulich wrote:
> Like x86/HVM's __hvm_copy(), Arm's copy_guest() is used for both 
> to-guest
> and from-guest copying. Naturally in the latter case the hypervisor 
> buffer
> needs writing to, hence the function parameter cannot be 
> pointer-to-const.
> 
> No functional change intended.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Reviewed-by: Nicola Vetrini <nicola.vetrini@bugseng.com>

See comment below, but I can do as a follow-up if you'd like.

> ---
> Of course for both the pre-existing x86 deviation and the new Arm one 
> it
> might be more robust if the deviation was also limited to the 
> respective
> source file. Can this be expressed together with the needed regex?

Yes, e.g.

-config=MC3A2.R11.8,reports+={safe,"any_area(any_loc(file(^xen/arch/arm/...$)&&text(^.*copy_guest.*COPY_to_guest 
doesn't modify.*$)))"}

not compile-tested, so YMMV.

> 
> --- a/automation/eclair_analysis/ECLAIR/deviations.ecl
> +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
> @@ -433,6 +433,12 @@ Fixing this violation would require to i
>  
> -config=MC3A2.R11.8,reports+={safe,"any_area(any_loc(any_exp(macro(^container_of$))))"}
>  -doc_end
> 
> +-doc_begin="Function copy_guest() in xen/arch/arm/guestcopy.c is a 
> double-use
> +function, where the parameter needs to not be const because it can be 
> set for
> +write or not"
> +-config=MC3A2.R11.8,reports+={safe,"any_area(any_loc(text(^.*copy_guest.*COPY_to_guest 
> doesn't modify.*$)))"}
> +-doc_end
> +
>  -doc_begin="Function __hvm_copy in xen/arch/x86/hvm/hvm.c is a 
> double-use
>  function, where the parameter needs to not be const because it can be 
> set for
>  write or not"
> --- a/xen/arch/arm/guestcopy.c
> +++ b/xen/arch/arm/guestcopy.c
> @@ -109,14 +109,16 @@ static unsigned long copy_guest(void *bu
> 
>  unsigned long raw_copy_to_guest(void *to, const void *from, unsigned 
> int len)
>  {
> -    return copy_guest((void *)from, (vaddr_t)to, len,
> -                      GVA_INFO(current), COPY_to_guest | COPY_linear);
> +    return copy_guest((void *)from, /* COPY_to_guest doesn't modify */
> +                      (vaddr_t)to, len, GVA_INFO(current),
> +                      COPY_to_guest | COPY_linear);
>  }
> 
>  unsigned long raw_copy_to_guest_flush_dcache(void *to, const void 
> *from,
>                                               unsigned int len)
>  {
> -    return copy_guest((void *)from, (vaddr_t)to, len, 
> GVA_INFO(current),
> +    return copy_guest((void *)from, /* COPY_to_guest doesn't modify */
> +                      (vaddr_t)to, len, GVA_INFO(current),
>                        COPY_to_guest | COPY_flush_dcache | 
> COPY_linear);
>  }

-- 
Nicola Vetrini, B.Sc.
Software Engineer
BUGSENG (https://bugseng.com)
LinkedIn: https://www.linkedin.com/in/nicola-vetrini-a42471253