[Xen-devel] [PATCH] x86: allow grant table originating pte-s to have their guest available bits set

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

In order to allow 2.6.27's get_user_pages_fast() to correctly detect
granted pages (so they would be passed to get_user_pages()), it must be
possible to tell the grant table code in Xen to set the three available
bits in the pte-s it creates.

While not applicable to the 2.6.18 tree, I'm nevertheless attaching our
Linux side patch for reference.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

Index: 2008-10-27/xen/arch/x86/mm.c
===================================================================
--- 2008-10-27.orig/xen/arch/x86/mm.c   2008-10-31 16:13:56.000000000 +0100
+++ 2008-10-27/xen/arch/x86/mm.c        2008-10-31 17:41:12.000000000 +0100
@@ -3326,6 +3326,10 @@ int create_grant_host_mapping(uint64_t a
     if ( !(flags & GNTMAP_readonly) )
         l1e_add_flags(pte,_PAGE_RW);
 
+    l1e_add_flags(pte,
+                  ((flags >> _GNTMAP_guest_avail0) * _PAGE_AVAIL0)
+                   & _PAGE_AVAIL);
+
     l1e_add_flags(pte, cacheattr_to_pte_flags(cache_flags >> 5));
 
     if ( flags & GNTMAP_contains_pte )
Index: 2008-10-27/xen/common/kernel.c
===================================================================
--- 2008-10-27.orig/xen/common/kernel.c 2008-10-27 11:25:15.000000000 +0100
+++ 2008-10-27/xen/common/kernel.c      2008-10-31 17:17:30.000000000 +0100
@@ -222,7 +222,8 @@ DO(xen_version)(int cmd, XEN_GUEST_HANDL
 #ifdef CONFIG_X86
             if ( !is_hvm_vcpu(current) )
                 fi.submap |= (1U << XENFEAT_mmu_pt_update_preserve_ad) |
-                             (1U << XENFEAT_highmem_assist);
+                             (1U << XENFEAT_highmem_assist) |
+                             (1U << XENFEAT_gnttab_map_avail_bits);
 #endif
             break;
         default:
Index: 2008-10-27/xen/include/public/features.h
===================================================================
--- 2008-10-27.orig/xen/include/public/features.h       2008-10-27 
11:24:26.000000000 +0100
+++ 2008-10-27/xen/include/public/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: 2008-10-27/xen/include/public/grant_table.h
===================================================================
--- 2008-10-27.orig/xen/include/public/grant_table.h    2007-12-07 
11:51:50.000000000 +0100
+++ 2008-10-27/xen/include/public/grant_table.h 2008-10-31 17:10:21.000000000 
+0100
@@ -360,7 +360,7 @@ 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)
@@ -388,6 +388,13 @@ 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.                        */

Attachment: xen-grant-pte-special.patch
Description: Text document

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel