As of 8cc5036bc385 ("x86/pv: Fix ABAC cmpxchg() race in
_get_page_type()") this no longer needs passing separately - the type
can now be read from struct page_info, as the call now happens after its
writing.

While there also constify the 2nd parameter.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/include/asm/shadow.h
+++ b/xen/arch/x86/include/asm/shadow.h
@@ -84,8 +84,8 @@ void shadow_final_teardown(struct domain
 void sh_remove_shadows(struct domain *d, mfn_t gmfn, int fast, int all);
 
 /* Adjust shadows ready for a guest page to change its type. */
-void shadow_prepare_page_type_change(struct domain *d, struct page_info *page,
-                                     unsigned long new_type);
+void shadow_prepare_page_type_change(struct domain *d,
+                                     const struct page_info *page);
 
 /* Discard _all_ mappings from the domain's shadows. */
 void shadow_blow_tables_per_domain(struct domain *d);
@@ -113,8 +113,7 @@ static inline void sh_remove_shadows(str
                                      int fast, int all) {}
 
 static inline void shadow_prepare_page_type_change(struct domain *d,
-                                                   struct page_info *page,
-                                                   unsigned long new_type) {}
+                                                   const struct page_info *page) {}
 
 static inline void shadow_blow_tables_per_domain(struct domain *d) {}
 
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -3018,7 +3018,7 @@ static int _get_page_type(struct page_in
         struct domain *d = page_get_owner(page);
 
         if ( d && shadow_mode_enabled(d) )
-            shadow_prepare_page_type_change(d, page, type);
+            shadow_prepare_page_type_change(d, page);
 
         if ( (x & PGT_type_mask) != type )
         {
--- a/xen/arch/x86/mm/shadow/common.c
+++ b/xen/arch/x86/mm/shadow/common.c
@@ -2265,8 +2265,8 @@ void sh_remove_shadows(struct domain *d,
     paging_unlock(d);
 }
 
-void shadow_prepare_page_type_change(struct domain *d, struct page_info *page,
-                                     unsigned long new_type)
+void shadow_prepare_page_type_change(struct domain *d,
+                                     const struct page_info *page)
 {
     if ( !(page->count_info & PGC_page_table) )
         return;
@@ -2278,7 +2278,7 @@ void shadow_prepare_page_type_change(str
      * pages are allowed to become writeable.
      */
     if ( (page->shadow_flags & SHF_oos_may_write) &&
-         new_type == PGT_writable_page )
+         (page->u.inuse.type_info & PGT_type_mask) == PGT_writable_page )
         return;
 #endif

On 26/07/2022 17:03, Jan Beulich wrote:
> As of 8cc5036bc385 ("x86/pv: Fix ABAC cmpxchg() race in
> _get_page_type()") this no longer needs passing separately - the type
> can now be read from struct page_info, as the call now happens after its
> writing.
>
> While there also constify the 2nd parameter.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>