Out-of-sync L1 shadows: OOS base

diff -r 26ecd1f9e128 xen/arch/x86/mm.c
@@ -1933,9 +1933,15 @@ int get_page_type(struct page_info *page
         {
             struct domain *d = page_get_owner(page);
 
-            /* Never allow a shadowed frame to go from type count 0 to 1 */
-            if ( d && shadow_mode_enabled(d) )
-                shadow_remove_all_shadows(d->vcpu[0], _mfn(page_to_mfn(page)));
+            /* Normally we should never let a page go from type count 0
+             * to type count 1 when it is shadowed. One exception:
+             * out-of-sync shadowed pages are allowed to become
+             * writeable. */
+            if ( d && shadow_mode_enabled(d)
+                 && (page->count_info & PGC_page_table)
+                 && !((page->shadow_flags & (1u<<29))
+                      && type == PGT_writable_page) )
+               shadow_remove_all_shadows(d->vcpu[0], _mfn(page_to_mfn(page)));
 
             ASSERT(!(x & PGT_pae_xen_l2));
             if ( (x & PGT_type_mask) != type )

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diff -r 26ecd1f9e128 xen/arch/x86/mm/shadow/multi.h
@@ -115,3 +115,13 @@ SHADOW_INTERNAL_NAME(sh_destroy_monitor_
 
 extern struct paging_mode 
 SHADOW_INTERNAL_NAME(sh_paging_mode, GUEST_LEVELS);
+
+#if SHADOW_OPTIMIZATIONS & SHOPT_OUT_OF_SYNC
+extern void 
+SHADOW_INTERNAL_NAME(sh_resync_l1, GUEST_LEVELS)
+    (struct vcpu *v, mfn_t gmfn);
+
+extern int
+SHADOW_INTERNAL_NAME(sh_safe_not_to_sync, GUEST_LEVELS)
+     (struct vcpu*v, mfn_t gmfn);
+#endif

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diff -r 26ecd1f9e128 xen/arch/x86/mm/shadow/types.h
@@ -438,6 +438,10 @@ struct shadow_walk_t
 #define sh_guess_wrmap             INTERNAL_NAME(sh_guess_wrmap)
 #define sh_clear_shadow_entry      INTERNAL_NAME(sh_clear_shadow_entry)
 
+#if SHADOW_OPTIMIZATIONS & SHOPT_OUT_OF_SYNC
+#define sh_resync_l1               INTERNAL_NAME(sh_resync_l1)
+#define sh_safe_not_to_sync        INTERNAL_NAME(sh_safe_not_to_sync)
+#endif
 
 /* The sh_guest_(map|get)_* functions depends on Xen's paging levels */
 #define sh_guest_map_l1e \

diff -r 26ecd1f9e128 xen/include/asm-x86/domain.h
@@ -103,6 +103,9 @@ struct shadow_domain {
      * emulation and remove write permission
      */
     atomic_t          gtable_dirty_version;
+
+    /* OOS */
+    int oos_active;
 };
 
 struct shadow_vcpu {

@@ -122,6 +125,10 @@ struct shadow_vcpu {
     unsigned long last_emulated_frame;
     /* Last MFN that we emulated a write successfully */
     unsigned long last_emulated_mfn;
+
+    /* Shadow out-of-sync: pages that this vcpu has let go out of sync */
+    mfn_t oos[SHADOW_OOS_PAGES];
+    unsigned long oos_va[SHADOW_OOS_PAGES];
 };
 
 /************************************************/

diff -r 26ecd1f9e128 xen/include/asm-x86/mm.h
@@ -130,6 +130,9 @@ static inline u32 pickle_domptr(struct d
 /* The order of the largest allocation unit we use for shadow pages */
 #define SHADOW_MAX_ORDER 2 /* Need up to 16k allocs for 32-bit on PAE/64 */
 
+/* The number of out-of-sync shadows we allow per vcpu (prime, please) */
+#define SHADOW_OOS_PAGES 7
+
 #define page_get_owner(_p)    (unpickle_domptr((_p)->u.inuse._domain))
 #define page_set_owner(_p,_d) ((_p)->u.inuse._domain = pickle_domptr(_d))
 

diff -r 26ecd1f9e128 xen/include/asm-x86/perfc_defn.h
@@ -80,6 +80,7 @@ PERFCOUNTER(shadow_writeable_h_3,  "shad
 PERFCOUNTER(shadow_writeable_h_3,  "shadow writeable: 64b w2k3")
 PERFCOUNTER(shadow_writeable_h_4,  "shadow writeable: linux low/solaris")
 PERFCOUNTER(shadow_writeable_h_5,  "shadow writeable: linux high")
+PERFCOUNTER(shadow_writeable_h_6,  "shadow writeable: unsync va")
 PERFCOUNTER(shadow_writeable_bf,   "shadow writeable brute-force")
 PERFCOUNTER(shadow_mappings,       "shadow removes all mappings")
 PERFCOUNTER(shadow_mappings_bf,    "shadow rm-mappings brute-force")

@@ -101,4 +102,8 @@ PERFCOUNTER(shadow_em_ex_non_pt,   "shad
 PERFCOUNTER(shadow_em_ex_non_pt,   "shadow extra non-pt-write op")
 PERFCOUNTER(shadow_em_ex_fail,     "shadow extra emulation failed")
 
+PERFCOUNTER(shadow_unsync,         "shadow OOS unsyncs")
+PERFCOUNTER(shadow_unsync_evict,   "shadow OOS evictions")
+PERFCOUNTER(shadow_resync,         "shadow OOS resyncs")
+
 /*#endif*/ /* __XEN_PERFC_DEFN_H__ */