xen/mm: remove aliasing of PGC_need_scrub over PGC_allocated

Future changes will care about the state of the PGC_need_scrub flag even
when pages have the PGC_allocated set, and hence it's no longer possible to
alias both values.  Also introduce PGC_need_scrub to the set of preserved
flags, so it's not dropped by assign_pages().

No functional change intended, albeit the page counter on x86 looses a bit.

Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/arch/arm/include/asm/mm.h

@@ -144,6 +144,9 @@ struct page_info
 #define _PGC_colored      PG_shift(4)
 #define PGC_colored       PG_mask(1, 4)
 #endif
+/* Page needs to be scrubbed. */
+#define _PGC_need_scrub   PG_shift(5)
+#define PGC_need_scrub    PG_mask(1, 5)
 /* ... */
 /* Page is broken? */
 #define _PGC_broken       PG_shift(7)
@@ -163,13 +166,6 @@ struct page_info
 #define PGC_count_width   PG_shift(10)
 #define PGC_count_mask    ((1UL<<PGC_count_width)-1)
 
-/*
- * Page needs to be scrubbed. Since this bit can only be set on a page that is
- * free (i.e. in PGC_state_free) we can reuse PGC_allocated bit.
- */
-#define _PGC_need_scrub   _PGC_allocated
-#define PGC_need_scrub    PGC_allocated
-
 #if defined(CONFIG_ARM_64) || defined(CONFIG_MPU)
 #define is_xen_heap_page(page) ((page)->count_info & PGC_xen_heap)
 #define is_xen_heap_mfn(mfn) \

xen/arch/ppc/include/asm/mm.h

@@ -57,6 +57,9 @@ static inline struct page_info *virt_to_page(const void *v)
 /* Page is Xen heap? */
 #define _PGC_xen_heap     PG_shift(2)
 #define PGC_xen_heap      PG_mask(1, 2)
+/* Page needs to be scrubbed. */
+#define _PGC_need_scrub   PG_shift(3)
+#define PGC_need_scrub    PG_mask(1, 3)
 /* Page is broken? */
 #define _PGC_broken       PG_shift(7)
 #define PGC_broken        PG_mask(1, 7)
@@ -75,13 +78,6 @@ static inline struct page_info *virt_to_page(const void *v)
 #define PGC_count_width   PG_shift(10)
 #define PGC_count_mask    ((1UL<<PGC_count_width)-1)
 
-/*
- * Page needs to be scrubbed. Since this bit can only be set on a page that is
- * free (i.e. in PGC_state_free) we can reuse PGC_allocated bit.
- */
-#define _PGC_need_scrub   _PGC_allocated
-#define PGC_need_scrub    PGC_allocated
-
 #define is_xen_heap_page(page) ((page)->count_info & PGC_xen_heap)
 #define is_xen_heap_mfn(mfn) \
     (mfn_valid(mfn) && is_xen_heap_page(mfn_to_page(mfn)))

xen/arch/riscv/include/asm/mm.h

@@ -273,13 +273,6 @@ static inline bool arch_mfns_in_directmap(unsigned long mfn, unsigned long nr)
 #define PGT_count_width   PG_shift(2)
 #define PGT_count_mask    ((1UL << PGT_count_width) - 1)
 
-/*
- * Page needs to be scrubbed. Since this bit can only be set on a page that is
- * free (i.e. in PGC_state_free) we can reuse PGC_allocated bit.
- */
-#define _PGC_need_scrub   _PGC_allocated
-#define PGC_need_scrub    PGC_allocated
-
 /* Cleared when the owning guest 'frees' this page. */
 #define _PGC_allocated    PG_shift(1)
 #define PGC_allocated     PG_mask(1, 1)
@@ -293,6 +286,9 @@ static inline bool arch_mfns_in_directmap(unsigned long mfn, unsigned long nr)
 #else
 #define PGC_static     0
 #endif
+/* Page needs to be scrubbed. */
+#define _PGC_need_scrub   PG_shift(4)
+#define PGC_need_scrub    PG_mask(1, 4)
 /* Page is broken? */
 #define _PGC_broken       PG_shift(7)
 #define PGC_broken        PG_mask(1, 7)

xen/arch/x86/include/asm/mm.h

@@ -83,29 +83,25 @@
 #define PGC_state_offlined  PG_mask(2, 6)
 #define PGC_state_free      PG_mask(3, 6)
 #define page_state_is(pg, st) (((pg)->count_info&PGC_state) == PGC_state_##st)
+/* Page needs to be scrubbed. */
+#define _PGC_need_scrub   PG_shift(7)
+#define PGC_need_scrub    PG_mask(1, 7)
 #ifdef CONFIG_SHADOW_PAGING
  /* Set when a page table page has been shadowed. */
-#define _PGC_shadowed_pt  PG_shift(7)
-#define PGC_shadowed_pt   PG_mask(1, 7)
+#define _PGC_shadowed_pt  PG_shift(8)
+#define PGC_shadowed_pt   PG_mask(1, 8)
 #else
 #define PGC_shadowed_pt   0
 #endif
 
 /* Count of references to this frame. */
 #if PGC_shadowed_pt
-#define PGC_count_width   PG_shift(7)
+#define PGC_count_width   PG_shift(8)
 #else
-#define PGC_count_width   PG_shift(6)
+#define PGC_count_width   PG_shift(7)
 #endif
 #define PGC_count_mask    ((1UL<<PGC_count_width)-1)
 
-/*
- * Page needs to be scrubbed. Since this bit can only be set on a page that is
- * free (i.e. in PGC_state_free) we can reuse PGC_allocated bit.
- */
-#define _PGC_need_scrub   _PGC_allocated
-#define PGC_need_scrub    PGC_allocated
-
 #ifndef CONFIG_BIGMEM
 /*
  * This definition is solely for the use in struct page_info (and

xen/common/page_alloc.c

@@ -170,7 +170,7 @@
 /*
  * Flags that are preserved in assign_pages() (and only there)
  */
-#define PGC_preserved (PGC_extra | PGC_static | PGC_colored)
+#define PGC_preserved (PGC_extra | PGC_static | PGC_colored | PGC_need_scrub)
 
 #ifndef PGT_TYPE_INFO_INITIALIZER
 #define PGT_TYPE_INFO_INITIALIZER 0