From: jbeulich@xxxxxxxxxx
Subject: properly mark mapped grant pages as special for get_user_pages_fast()
Patch-mainline: obsolete

Should be merged into the 2.6.27 patch.

Index: head-2008-10-29/drivers/xen/core/gnttab.c
===================================================================
--- head-2008-10-29.orig/drivers/xen/core/gnttab.c	2008-11-03 11:49:51.000000000 +0100
+++ head-2008-10-29/drivers/xen/core/gnttab.c	2008-11-03 15:18:39.000000000 +0100
@@ -630,6 +630,76 @@ void __gnttab_dma_map_page(struct page *
 	} while (unlikely(read_seqretry(&gnttab_dma_lock, seq)));
 }
 
+#ifdef __HAVE_ARCH_PTE_SPECIAL
+
+static unsigned int GNTMAP_pte_special;
+
+bool gnttab_pre_map_adjust(unsigned int cmd, struct gnttab_map_grant_ref *map,
+			   unsigned int count)
+{
+	unsigned int i;
+	bool fixup;
+
+	if (unlikely(cmd != GNTTABOP_map_grant_ref))
+		count = 0;
+
+	for (i = 0, fixup = false; i < count; ++i, ++map) {
+		if (!(map->flags & GNTMAP_host_map)
+		    || !(map->flags & GNTMAP_application_map))
+			continue;
+		if (GNTMAP_pte_special)
+			map->flags |= GNTMAP_pte_special;
+		else
+			fixup = true;
+	}
+
+	BUG_ON(fixup && xen_feature(XENFEAT_auto_translated_physmap));
+
+	return fixup;
+}
+EXPORT_SYMBOL(gnttab_pre_map_adjust);
+
+#if CONFIG_XEN_COMPAT < 0x030400
+int gnttab_post_map_adjust(const struct gnttab_map_grant_ref *map, unsigned int count)
+{
+	unsigned int i;
+	int rc = 0;
+
+	for (i = 0; i < count && rc == 0; ++i, ++map) {
+		pte_t pte;
+
+		if (!(map->flags & GNTMAP_host_map)
+		    || !(map->flags & GNTMAP_application_map))
+			continue;
+
+#ifdef CONFIG_X86
+		pte = __pte_ma((map->dev_bus_addr | _PAGE_PRESENT | _PAGE_USER
+				| _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_NX
+				| _PAGE_SPECIAL)
+			       & __supported_pte_mask);
+#else
+#error Architecture not yet supported.
+#endif
+		if (!(map->flags & GNTMAP_readonly))
+			pte = pte_mkwrite(pte);
+
+		if (map->flags & GNTMAP_contains_pte) {
+			mmu_update_t u;
+
+			u.ptr = map->host_addr;
+			u.val = __pte_val(pte);
+			rc = HYPERVISOR_mmu_update(&u, 1, NULL, DOMID_SELF);
+		} else
+			rc = HYPERVISOR_update_va_mapping(map->host_addr, pte, 0);
+	}
+
+	return rc;
+}
+EXPORT_SYMBOL(gnttab_post_map_adjust);
+#endif
+
+#endif /* __HAVE_ARCH_PTE_SPECIAL */
+
 static int gnttab_resume(struct sys_device *dev)
 {
 	if (max_nr_grant_frames() < nr_grant_frames)
@@ -781,6 +851,18 @@ int __devinit gnttab_init(void)
 	gnttab_free_count = nr_init_grefs - NR_RESERVED_ENTRIES;
 	gnttab_free_head  = NR_RESERVED_ENTRIES;
 
+#ifdef __HAVE_ARCH_PTE_SPECIAL
+	if (!xen_feature(XENFEAT_auto_translated_physmap)
+	    && xen_feature(XENFEAT_gnttab_map_avail_bits)) {
+#ifdef CONFIG_X86
+		GNTMAP_pte_special = (__pte_val(pte_mkspecial(__pte_ma(0)))
+				      >> _PAGE_BIT_UNUSED1) << _GNTMAP_guest_avail0;
+#else
+#error Architecture not yet supported.
+#endif
+	}
+#endif
+
 	return 0;
 
  ini_nomem:
Index: head-2008-10-29/include/asm-x86/mach-xen/asm/hypercall_32.h
===================================================================
--- head-2008-10-29.orig/include/asm-x86/mach-xen/asm/hypercall_32.h	2008-11-03 11:49:51.000000000 +0100
+++ head-2008-10-29/include/asm-x86/mach-xen/asm/hypercall_32.h	2008-11-03 13:26:27.000000000 +0100
@@ -332,9 +332,19 @@ static inline int __must_check
 HYPERVISOR_grant_table_op(
 	unsigned int cmd, void *uop, unsigned int count)
 {
+	bool fixup = false;
+	int rc;
+
 	if (arch_use_lazy_mmu_mode())
 		xen_multicall_flush(false);
-	return _hypercall3(int, grant_table_op, cmd, uop, count);
+#ifdef GNTTABOP_map_grant_ref
+	if (cmd == GNTTABOP_map_grant_ref)
+#endif
+		fixup = gnttab_pre_map_adjust(cmd, uop, count);
+	rc = _hypercall3(int, grant_table_op, cmd, uop, count);
+	if (rc == 0 && fixup)
+		rc = gnttab_post_map_adjust(uop, count);
+	return rc;
 }
 
 static inline int __must_check
Index: head-2008-10-29/include/asm-x86/mach-xen/asm/hypercall_64.h
===================================================================
--- head-2008-10-29.orig/include/asm-x86/mach-xen/asm/hypercall_64.h	2008-11-03 11:49:51.000000000 +0100
+++ head-2008-10-29/include/asm-x86/mach-xen/asm/hypercall_64.h	2008-11-03 13:26:20.000000000 +0100
@@ -324,9 +324,19 @@ static inline int __must_check
 HYPERVISOR_grant_table_op(
 	unsigned int cmd, void *uop, unsigned int count)
 {
+	bool fixup = false;
+	int rc;
+
 	if (arch_use_lazy_mmu_mode())
 		xen_multicall_flush(false);
-	return _hypercall3(int, grant_table_op, cmd, uop, count);
+#ifdef GNTTABOP_map_grant_ref
+	if (cmd == GNTTABOP_map_grant_ref)
+#endif
+		fixup = gnttab_pre_map_adjust(cmd, uop, count);
+	rc = _hypercall3(int, grant_table_op, cmd, uop, count);
+	if (rc == 0 && fixup)
+		rc = gnttab_post_map_adjust(uop, count);
+	return rc;
 }
 
 static inline int __must_check
Index: head-2008-10-29/include/asm-x86/mach-xen/asm/hypervisor.h
===================================================================
--- head-2008-10-29.orig/include/asm-x86/mach-xen/asm/hypervisor.h	2008-11-03 11:49:51.000000000 +0100
+++ head-2008-10-29/include/asm-x86/mach-xen/asm/hypervisor.h	2008-11-03 15:18:37.000000000 +0100
@@ -166,6 +166,20 @@ static inline bool arch_use_lazy_mmu_mod
 	       && xen_use_lazy_mmu_mode();
 }
 
+struct gnttab_map_grant_ref;
+bool gnttab_pre_map_adjust(unsigned int cmd, struct gnttab_map_grant_ref *,
+			   unsigned int count);
+#if CONFIG_XEN_COMPAT < 0x030400
+int gnttab_post_map_adjust(const struct gnttab_map_grant_ref *, unsigned int);
+#else
+static inline int gnttab_post_map_adjust(const struct gnttab_map_grant_ref *m,
+					 unsigned int count)
+{
+	BUG();
+	return -ENOSYS;
+}
+#endif
+
 #else /* CONFIG_XEN */
 
 static inline void xen_multicall_flush(bool ignore) {}
@@ -174,6 +188,9 @@ static inline bool arch_use_lazy_mmu_mod
 #define xen_multi_mmu_update(...) ({ BUG(); -ENOSYS; })
 #define xen_multi_mmuext_op(...) ({ BUG(); -ENOSYS; })
 
+#define gnttab_pre_map_adjust(...) false
+#define gnttab_post_map_adjust(...) ({ BUG(); -ENOSYS; })
+
 #endif /* CONFIG_XEN */
 
 #include <xen/hypercall.h>
Index: head-2008-10-29/include/xen/interface/features.h
===================================================================
--- head-2008-10-29.orig/include/xen/interface/features.h	2008-10-29 09:55:56.000000000 +0100
+++ head-2008-10-29/include/xen/interface/features.h	2008-10-31 17:03:12.000000000 +0100
@@ -62,6 +62,12 @@
 /* x86: Does this Xen host support the MMU_{CLEAR,COPY}_PAGE hypercall? */
 #define XENFEAT_highmem_assist             6
 
+/*
+ * If set, GNTTABOP_map_grant_ref honors flags to be placed into guest kernel
+ * available pte bits.
+ */
+#define XENFEAT_gnttab_map_avail_bits      7
+
 #define XENFEAT_NR_SUBMAPS 1
 
 #endif /* __XEN_PUBLIC_FEATURES_H__ */
Index: head-2008-10-29/include/xen/interface/grant_table.h
===================================================================
--- head-2008-10-29.orig/include/xen/interface/grant_table.h	2008-10-29 11:25:35.000000000 +0100
+++ head-2008-10-29/include/xen/interface/grant_table.h	2008-10-31 17:10:21.000000000 +0100
@@ -367,7 +367,7 @@ DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_and
 
 
 /*
- * Bitfield values for update_pin_status.flags.
+ * Bitfield values for gnttab_map_grant_ref.flags.
  */
  /* Map the grant entry for access by I/O devices. */
 #define _GNTMAP_device_map      (0)
@@ -395,6 +395,13 @@ DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_and
 #define GNTMAP_contains_pte     (1<<_GNTMAP_contains_pte)
 
 /*
+ * Bits to be placed in guest kernel available PTE bits (architecture
+ * dependent; only supported when XENFEAT_gnttab_map_avail_bits is set).
+ */
+#define _GNTMAP_guest_avail0    (16)
+#define GNTMAP_guest_avail_mask ((uint32_t)~0 << _GNTMAP_guest_avail0)
+
+/*
  * Values for error status returns. All errors are -ve.
  */
 #define GNTST_okay             (0)  /* Normal return.                        */