[Xen-devel] [PATCH 1/2] xen/mm: fold PGC_broken into PGC_state bits

[David Woodhouse <dwmw2@infradead.org>]

From: David Woodhouse <dwmw@amazon.co.uk>

Only PGC_state_offlining and PGC_state_offlined are valid in conjunction
with PGC_broken. The other two states (free and inuse) were never valid
for a broken page.

By folding PGC_broken in, we can have three bits for PGC_state which
allows up to 8 states, of which 6 are currently used and 2 are available
for new use cases.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 xen/arch/x86/domctl.c    |  2 +-
 xen/common/page_alloc.c  | 66 ++++++++++++++++++++++------------------
 xen/include/asm-arm/mm.h | 38 +++++++++++++++--------
 xen/include/asm-x86/mm.h | 36 ++++++++++++++++------
 4 files changed, 89 insertions(+), 53 deletions(-)

diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
index ed86762fa6..a411f64afa 100644
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -422,7 +422,7 @@ long arch_do_domctl(
                 if ( page->u.inuse.type_info & PGT_pinned )
                     type |= XEN_DOMCTL_PFINFO_LPINTAB;
 
-                if ( page->count_info & PGC_broken )
+                if ( page_is_broken(page) )
                     type = XEN_DOMCTL_PFINFO_BROKEN;
             }
 
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 76d37226df..8d72a64f4e 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -1093,7 +1093,7 @@ static int reserve_offlined_page(struct page_info *head)
         struct page_info *pg;
         int next_order;
 
-        if ( page_state_is(cur_head, offlined) )
+        if ( page_is_offlined(cur_head) )
         {
             cur_head++;
             if ( first_dirty != INVALID_DIRTY_IDX && first_dirty )
@@ -1113,7 +1113,7 @@ static int reserve_offlined_page(struct page_info *head)
             for ( i = (1 << cur_order), pg = cur_head + (1 << cur_order );
                   i < (1 << next_order);
                   i++, pg++ )
-                if ( page_state_is(pg, offlined) )
+                if ( page_is_offlined(pg) )
                     break;
             if ( i == ( 1 << next_order) )
             {
@@ -1145,16 +1145,20 @@ static int reserve_offlined_page(struct page_info *head)
 
     for ( cur_head = head; cur_head < head + ( 1UL << head_order); cur_head++ )
     {
-        if ( !page_state_is(cur_head, offlined) )
+        struct page_list_head *list;
+
+        if ( page_state_is(cur_head, offlined) )
+            list = &page_offlined_list;
+        else if (page_state_is(cur_head, broken) )
+            list = &page_broken_list;
+        else
             continue;
 
         avail[node][zone]--;
         total_avail_pages--;
         ASSERT(total_avail_pages >= 0);
 
-        page_list_add_tail(cur_head,
-                           test_bit(_PGC_broken, &cur_head->count_info) ?
-                           &page_broken_list : &page_offlined_list);
+        page_list_add_tail(cur_head, list);
 
         count++;
     }
@@ -1404,13 +1408,16 @@ static void free_heap_pages(
         switch ( pg[i].count_info & PGC_state )
         {
         case PGC_state_inuse:
-            BUG_ON(pg[i].count_info & PGC_broken);
             pg[i].count_info = PGC_state_free;
             break;
 
         case PGC_state_offlining:
-            pg[i].count_info = (pg[i].count_info & PGC_broken) |
-                               PGC_state_offlined;
+            pg[i].count_info = PGC_state_offlined;
+            tainted = 1;
+            break;
+
+        case PGC_state_broken_offlining:
+            pg[i].count_info = PGC_state_broken;
             tainted = 1;
             break;
 
@@ -1527,16 +1534,16 @@ static unsigned long mark_page_offline(struct page_info *pg, int broken)
     do {
         nx = x = y;
 
-        if ( ((x & PGC_state) != PGC_state_offlined) &&
-             ((x & PGC_state) != PGC_state_offlining) )
-        {
-            nx &= ~PGC_state;
-            nx |= (((x & PGC_state) == PGC_state_free)
-                   ? PGC_state_offlined : PGC_state_offlining);
-        }
+        nx &= ~PGC_state;
 
-        if ( broken )
-            nx |= PGC_broken;
+        /* If it was already broken, it stays broken */
+        if ( pgc_is_broken(x) )
+            broken = 1;
+
+        if ( pgc_is_offlined(x) || pgc_is(x, free) )
+            nx |= broken ? PGC_state_broken : PGC_state_offlined;
+        else
+            nx |= broken ? PGC_state_broken_offlining : PGC_state_offlining;
 
         if ( x == nx )
             break;
@@ -1609,7 +1616,7 @@ int offline_page(mfn_t mfn, int broken, uint32_t *status)
      * need to prevent malicious guest access the broken page again.
      * Under such case, hypervisor shutdown guest, preventing recursive mce.
      */
-    if ( (pg->count_info & PGC_broken) && (owner = page_get_owner(pg)) )
+    if ( page_is_broken(pg) && (owner = page_get_owner(pg)) )
     {
         *status = PG_OFFLINE_AGAIN;
         domain_crash(owner);
@@ -1620,7 +1627,7 @@ int offline_page(mfn_t mfn, int broken, uint32_t *status)
 
     old_info = mark_page_offline(pg, broken);
 
-    if ( page_state_is(pg, offlined) )
+    if ( page_is_offlined(pg) )
     {
         reserve_heap_page(pg);
 
@@ -1699,19 +1706,18 @@ unsigned int online_page(mfn_t mfn, uint32_t *status)
     do {
         ret = *status = 0;
 
-        if ( y & PGC_broken )
+        if ( pgc_is_broken(y) )
         {
             ret = -EINVAL;
-            *status = PG_ONLINE_FAILED |PG_ONLINE_BROKEN;
+            *status = PG_ONLINE_FAILED | PG_ONLINE_BROKEN;
             break;
         }
-
-        if ( (y & PGC_state) == PGC_state_offlined )
+        else if ( pgc_is(y, offlined) )
         {
             page_list_del(pg, &page_offlined_list);
             *status = PG_ONLINE_ONLINED;
         }
-        else if ( (y & PGC_state) == PGC_state_offlining )
+        else if ( pgc_is(y, offlining) )
         {
             *status = PG_ONLINE_ONLINED;
         }
@@ -1726,7 +1732,7 @@ unsigned int online_page(mfn_t mfn, uint32_t *status)
 
     spin_unlock(&heap_lock);
 
-    if ( (y & PGC_state) == PGC_state_offlined )
+    if ( pgc_is(y, offlined) )
         free_heap_pages(pg, 0, false);
 
     return ret;
@@ -1747,11 +1753,11 @@ int query_page_offline(mfn_t mfn, uint32_t *status)
 
     pg = mfn_to_page(mfn);
 
-    if ( page_state_is(pg, offlining) )
+    if ( page_is_offlining(pg) )
         *status |= PG_OFFLINE_STATUS_OFFLINE_PENDING;
-    if ( pg->count_info & PGC_broken )
+    if ( page_is_broken(pg) )
         *status |= PG_OFFLINE_STATUS_BROKEN;
-    if ( page_state_is(pg, offlined) )
+    if ( page_is_offlined(pg) )
         *status |= PG_OFFLINE_STATUS_OFFLINED;
 
     spin_unlock(&heap_lock);
@@ -2519,7 +2525,7 @@ __initcall(pagealloc_keyhandler_init);
 
 void scrub_one_page(struct page_info *pg)
 {
-    if ( unlikely(pg->count_info & PGC_broken) )
+    if ( unlikely(page_is_broken(pg)) )
         return;
 
 #ifndef NDEBUG
diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h
index 7df91280bc..a877791d1c 100644
--- a/xen/include/asm-arm/mm.h
+++ b/xen/include/asm-arm/mm.h
@@ -108,21 +108,35 @@ struct page_info
   /* Page is Xen heap? */
 #define _PGC_xen_heap     PG_shift(2)
 #define PGC_xen_heap      PG_mask(1, 2)
-/* ... */
-/* Page is broken? */
-#define _PGC_broken       PG_shift(7)
-#define PGC_broken        PG_mask(1, 7)
- /* Mutually-exclusive page states: { inuse, offlining, offlined, free }. */
-#define PGC_state         PG_mask(3, 9)
-#define PGC_state_inuse   PG_mask(0, 9)
-#define PGC_state_offlining PG_mask(1, 9)
-#define PGC_state_offlined PG_mask(2, 9)
-#define PGC_state_free    PG_mask(3, 9)
-#define page_state_is(pg, st) (((pg)->count_info&PGC_state) == PGC_state_##st)
+ /*
+  * Mutually-exclusive page states:
+  * { inuse, offlining, offlined, free, broken_offlining, broken }
+  */
+#define PGC_state                  PG_mask(7, 9)
+#define PGC_state_inuse            PG_mask(0, 9)
+#define PGC_state_offlining        PG_mask(1, 9)
+#define PGC_state_offlined         PG_mask(2, 9)
+#define PGC_state_free             PG_mask(3, 9)
+#define PGC_state_broken_offlining PG_mask(4, 9) /* Broken and offlining */
+#define PGC_state_broken           PG_mask(5, 9) /* Broken and offlined */
+
+#define pgc_is(pgc, st)            (((pgc) & PGC_state) == PGC_state_##st)
+#define page_state_is(pg, st)       pgc_is((pg)->count_info, st)
+
+#define pgc_is_broken(pgc)         (pgc_is(pgc, broken) || \
+                                    pgc_is(pgc, broken_offlining))
+#define pgc_is_offlined(pgc)       (pgc_is(pgc, offlined) || \
+                                    pgc_is(pgc, broken))
+#define pgc_is_offlining(pgc)      (pgc_is(pgc, offlining) || \
+                                    pgc_is(pgc, broken_offlining))
+
+#define page_is_broken(pg)         (pgc_is_broken((pg)->count_info))
+#define page_is_offlined(pg)       (pgc_is_broken((pg)->count_info))
+#define page_is_offlining(pg)      (pgc_is_broken((pg)->count_info))
+
 /* Page is not reference counted */
 #define _PGC_extra        PG_shift(10)
 #define PGC_extra         PG_mask(1, 10)
-
 /* Count of references to this frame. */
 #define PGC_count_width   PG_shift(10)
 #define PGC_count_mask    ((1UL<<PGC_count_width)-1)
diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
index a06b2fb81f..1203f1b179 100644
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -67,16 +67,32 @@
  /* 3-bit PAT/PCD/PWT cache-attribute hint. */
 #define PGC_cacheattr_base PG_shift(6)
 #define PGC_cacheattr_mask PG_mask(7, 6)
- /* Page is broken? */
-#define _PGC_broken       PG_shift(7)
-#define PGC_broken        PG_mask(1, 7)
- /* Mutually-exclusive page states: { inuse, offlining, offlined, free }. */
-#define PGC_state         PG_mask(3, 9)
-#define PGC_state_inuse   PG_mask(0, 9)
-#define PGC_state_offlining PG_mask(1, 9)
-#define PGC_state_offlined PG_mask(2, 9)
-#define PGC_state_free    PG_mask(3, 9)
-#define page_state_is(pg, st) (((pg)->count_info&PGC_state) == PGC_state_##st)
+ /*
+  * Mutually-exclusive page states:
+  * { inuse, offlining, offlined, free, broken_offlining, broken }
+  */
+#define PGC_state                  PG_mask(7, 9)
+#define PGC_state_inuse            PG_mask(0, 9)
+#define PGC_state_offlining        PG_mask(1, 9)
+#define PGC_state_offlined         PG_mask(2, 9)
+#define PGC_state_free             PG_mask(3, 9)
+#define PGC_state_broken_offlining PG_mask(4, 9) /* Broken and offlining */
+#define PGC_state_broken           PG_mask(5, 9) /* Broken and offlined */
+
+#define pgc_is(pgc, st)            (((pgc) & PGC_state) == PGC_state_##st)
+#define page_state_is(pg, st)       pgc_is((pg)->count_info, st)
+
+#define pgc_is_broken(pgc)         (pgc_is(pgc, broken) || \
+                                    pgc_is(pgc, broken_offlining))
+#define pgc_is_offlined(pgc)       (pgc_is(pgc, offlined) || \
+                                    pgc_is(pgc, broken))
+#define pgc_is_offlining(pgc)      (pgc_is(pgc, offlining) || \
+                                    pgc_is(pgc, broken_offlining))
+
+#define page_is_broken(pg)         (pgc_is_broken((pg)->count_info))
+#define page_is_offlined(pg)       (pgc_is_broken((pg)->count_info))
+#define page_is_offlining(pg)      (pgc_is_broken((pg)->count_info))
+
 /* Page is not reference counted */
 #define _PGC_extra        PG_shift(10)
 #define PGC_extra         PG_mask(1, 10)
-- 
2.21.0


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