xen/arm: Rework the interface of p2m_cache_flush and use typesafe gfn

p2m_cache_flush is expecting GFNs in parameter and not MFNs. Rename
the variable to *gfn* and use typesafe to avoid possible misusage.

Also, modify the prototype of the function to describe the range
using the start and the number of GFNs. This will avoid to wonder
whether the end if inclusive or exclusive.

Note that the type of the parameters 'start' is changed from xen_pfn_t
(aka uint64_t) to gfn_t (aka unsigned long). This means that a truncation
will occur for ARM32. It is fine because it will always be encoded on 28
bits maximum (40 bits address).

Signed-off-by: Julien Grall <julien.grall@arm.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/domctl.c

@@ -30,7 +30,7 @@ long arch_do_domctl(struct xen_domctl *domctl, struct domain *d,
         if ( e < s )
             return -EINVAL;
 
-        return p2m_cache_flush(d, s, e);
+        return p2m_cache_flush(d, _gfn(s), domctl->u.cacheflush.nr_pfns);
     }
     case XEN_DOMCTL_bind_pt_irq:
     {

xen/arch/arm/p2m.c

@@ -1469,16 +1469,17 @@ int relinquish_p2m_mapping(struct domain *d)
                               d->arch.p2m.default_access);
 }
 
-int p2m_cache_flush(struct domain *d, xen_pfn_t start_mfn, xen_pfn_t end_mfn)
+int p2m_cache_flush(struct domain *d, gfn_t start, unsigned long nr)
 {
     struct p2m_domain *p2m = &d->arch.p2m;
+    gfn_t end = gfn_add(start, nr);
 
-    start_mfn = MAX(start_mfn, p2m->lowest_mapped_gfn);
-    end_mfn = MIN(end_mfn, p2m->max_mapped_gfn);
+    start = gfn_max(start, _gfn(p2m->lowest_mapped_gfn));
+    end = gfn_min(end, _gfn(p2m->max_mapped_gfn));
 
     return apply_p2m_changes(d, CACHEFLUSH,
-                             pfn_to_paddr(start_mfn),
-                             pfn_to_paddr(end_mfn),
+                             pfn_to_paddr(gfn_x(start)),
+                             pfn_to_paddr(gfn_x(end)),
                              pfn_to_paddr(mfn_x(INVALID_MFN)),
                              MATTR_MEM, 0, p2m_invalid,
                              d->arch.p2m.default_access);

xen/include/asm-arm/p2m.h

@@ -139,7 +139,7 @@ void p2m_dump_info(struct domain *d);
 mfn_t p2m_lookup(struct domain *d, gfn_t gfn, p2m_type_t *t);
 
 /* Clean & invalidate caches corresponding to a region of guest address space */
-int p2m_cache_flush(struct domain *d, xen_pfn_t start_mfn, xen_pfn_t end_mfn);
+int p2m_cache_flush(struct domain *d, gfn_t start, unsigned long nr);
 
 /* Setup p2m RAM mapping for domain d from start-end. */
 int p2m_populate_ram(struct domain *d, paddr_t start, paddr_t end);