Arm/guestcopy: deviate copy_guest() uses just like their x86 counterparts

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: Michal Orzel <michal.orzel@amd.com>
Reviewed-by: Nicola Vetrini <nicola.vetrini@bugseng.com>

automation/eclair_analysis/ECLAIR/deviations.ecl

@@ -433,6 +433,12 @@ Fixing this violation would require to increase code complexity and lower readab
 -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"

xen/arch/arm/guestcopy.c

@@ -109,14 +109,16 @@ static unsigned long copy_guest(void *buf, uint64_t addr, unsigned long len,
 
 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);
 }