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. */
xen-grant-pte-special.patch
Description: Text document
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