[Xen-devel] [PATCH 06/11] ARM: simplify page type handling

["Jan Beulich" <JBeulich@xxxxxxxx>]

There's no need to have anything here on ARM other than the distinction
between writable and non-writable pages (and even that could likely be
eliminated, but with a more intrusive change). Limit type to a single
bit and drop pinned and validated flags altogether.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
Note: Compile tested only.

--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -1113,8 +1113,7 @@ void share_xen_page_with_guest(struct pa
     spin_lock(&d->page_alloc_lock);
 
     /* The incremented type count pins as writable or read-only. */
-    page->u.inuse.type_info  = (readonly ? PGT_none : PGT_writable_page);
-    page->u.inuse.type_info |= PGT_validated | 1;
+    page->u.inuse.type_info = (readonly ? PGT_none : PGT_writable_page) | 1;
 
     page_set_owner(page, d);
     smp_wmb(); /* install valid domain ptr before updating refcnt. */
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -354,8 +354,10 @@ int guest_remove_page(struct domain *d,
 
     rc = guest_physmap_remove_page(d, _gfn(gmfn), mfn, 0);
 
+#ifdef _PGT_pinned
     if ( !rc && test_and_clear_bit(_PGT_pinned, &page->u.inuse.type_info) )
         put_page_and_type(page);
+#endif
 
     /*
      * With the lack of an IOMMU on some platforms, domains with DMA-capable
--- a/xen/include/asm-arm/mm.h
+++ b/xen/include/asm-arm/mm.h
@@ -77,20 +77,12 @@ struct page_info
 #define PG_shift(idx)   (BITS_PER_LONG - (idx))
 #define PG_mask(x, idx) (x ## UL << PG_shift(idx))
 
-#define PGT_none          PG_mask(0, 4)  /* no special uses of this page   */
-#define PGT_writable_page PG_mask(7, 4)  /* has writable mappings?         */
-#define PGT_type_mask     PG_mask(15, 4) /* Bits 28-31 or 60-63.           */
-
- /* Owning guest has pinned this page to its current type? */
-#define _PGT_pinned       PG_shift(5)
-#define PGT_pinned        PG_mask(1, 5)
-
- /* Has this page been validated for use as its current type? */
-#define _PGT_validated    PG_shift(6)
-#define PGT_validated     PG_mask(1, 6)
+#define PGT_none          PG_mask(0, 1)  /* no special uses of this page   */
+#define PGT_writable_page PG_mask(1, 1)  /* has writable mappings?         */
+#define PGT_type_mask     PG_mask(1, 1)  /* Bits 31 or 63.                 */
 
  /* Count of uses of this frame as its current type. */
-#define PGT_count_width   PG_shift(9)
+#define PGT_count_width   PG_shift(2)
 #define PGT_count_mask    ((1UL<<PGT_count_width)-1)
 
  /* Cleared when the owning guest 'frees' this page. */

Attachment: ARM-page-types.patch
Description: Text document

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