Enable valid_phys_addr_range for x86_64 and check whether the identity
mapping exists before reading /dev/mem. For reserved regions there is no
identity mappings any more and then cannot be read from /dev/mem.

Side effect is that dd of entire memory will not work any more, once there are
reserved holes in memory space.

TBD: Read reserved regions as 0xffff or something, and continue reading
across holes, till we reach the high_memory (end of memory).

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
---

Index: linux-2.6.24-rc/arch/x86/kernel/e820_64.c
===================================================================
--- linux-2.6.24-rc.orig/arch/x86/kernel/e820_64.c
+++ linux-2.6.24-rc/arch/x86/kernel/e820_64.c
@@ -220,6 +220,11 @@ int is_memory_all_valid(unsigned long st
 }
 EXPORT_SYMBOL_GPL(is_memory_all_valid);
 
+int valid_phys_addr_range(unsigned long addr, size_t count)
+{
+	return is_memory_all_valid(addr, addr + count);
+}
+
 /* 
  * Find a free area in a specific range. 
  */ 
Index: linux-2.6.24-rc/include/asm-x86/io_64.h
===================================================================
--- linux-2.6.24-rc.orig/include/asm-x86/io_64.h
+++ linux-2.6.24-rc/include/asm-x86/io_64.h
@@ -265,6 +265,15 @@ extern int iommu_bio_merge;
  */
 #define xlate_dev_kmem_ptr(p)	p
 
+#define ARCH_HAS_VALID_PHYS_ADDR_RANGE
+extern int valid_phys_addr_range (unsigned long addr, size_t count);
+
+static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
+{
+	return 1;
+}
+
+
 #endif /* __KERNEL__ */
 
 #endif

-- 
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