diff --git a/arch/ia64/kernel/efi.c b/arch/ia64/kernel/efi.c
index 9990320..2993748 100644
--- a/arch/ia64/kernel/efi.c
+++ b/arch/ia64/kernel/efi.c
@@ -677,27 +677,34 @@
 /*
  * Determines whether the memory at phys_addr supports the desired
  * attribute (WB, UC, etc).  If this returns 1, the caller can safely
- * access *size bytes at phys_addr with the specified attribute.
+ * access size bytes at phys_addr with the specified attribute.
  */
-static int
-efi_mem_attribute_range (unsigned long phys_addr, unsigned long *size, u64 attr)
+int
+efi_mem_attribute_range (unsigned long phys_addr, unsigned long size, u64 attr)
 {
+	unsigned long end = phys_addr + size;
 	efi_memory_desc_t *md = efi_memory_descriptor(phys_addr);
-	unsigned long md_end;
 
-	if (!md || (md->attribute & attr) != attr)
+	/*
+	 * Some firmware doesn't report MMIO regions in the EFI memory
+	 * map.  The Intel BigSur (a.k.a. HP i2000) has this problem.
+	 * On those platforms, we have to assume UC is valid everywhere.
+	 */
+	if (!md || (md->attribute & attr) != attr) {
+		if (attr == EFI_MEMORY_UC && !efi_memmap_has_mmio())
+			return 1;
 		return 0;
+	}
 
 	do {
-		md_end = efi_md_end(md);
-		if (phys_addr + *size <= md_end)
+		unsigned long md_end = efi_md_end(md);
+
+		if (end <= md_end)
 			return 1;
 
 		md = efi_memory_descriptor(md_end);
-		if (!md || (md->attribute & attr) != attr) {
-			*size = md_end - phys_addr;
-			return 1;
-		}
+		if (!md || (md->attribute & attr) != attr)
+			return 0;
 	} while (md);
 	return 0;
 }
@@ -708,7 +715,7 @@
  * control access size.
  */
 int
-valid_phys_addr_range (unsigned long phys_addr, unsigned long *size)
+valid_phys_addr_range (unsigned long phys_addr, unsigned long size)
 {
 	return efi_mem_attribute_range(phys_addr, size, EFI_MEMORY_WB);
 }
@@ -723,7 +730,7 @@
  * because that doesn't appear in the boot-time EFI memory map.
  */
 int
-valid_mmap_phys_addr_range (unsigned long phys_addr, unsigned long *size)
+valid_mmap_phys_addr_range (unsigned long phys_addr, unsigned long size)
 {
 	if (efi_mem_attribute_range(phys_addr, size, EFI_MEMORY_WB))
 		return 1;
@@ -731,14 +738,6 @@
 	if (efi_mem_attribute_range(phys_addr, size, EFI_MEMORY_UC))
 		return 1;
 
-	/*
-	 * Some firmware doesn't report MMIO regions in the EFI memory map.
-	 * The Intel BigSur (a.k.a. HP i2000) has this problem.  In this
-	 * case, we can't use the EFI memory map to validate mmap requests.
-	 */
-	if (!efi_memmap_has_mmio())
-		return 1;
-
 	return 0;
 }
 
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 26d0116..5245ba1 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -88,21 +88,15 @@
 }
 
 #ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
-static inline int valid_phys_addr_range(unsigned long addr, size_t *count)
+static inline int valid_phys_addr_range(unsigned long addr, size_t count)
 {
-	unsigned long end_mem;
-
-	end_mem = __pa(high_memory);
-	if (addr >= end_mem)
+	if (addr + count > __pa(high_memory))
 		return 0;
 
-	if (*count > end_mem - addr)
-		*count = end_mem - addr;
-
 	return 1;
 }
 
-static inline int valid_mmap_phys_addr_range(unsigned long addr, size_t *size)
+static inline int valid_mmap_phys_addr_range(unsigned long addr, size_t size)
 {
 	return 1;
 }
@@ -119,7 +113,7 @@
 	ssize_t read, sz;
 	char *ptr;
 
-	if (!valid_phys_addr_range(p, &count))
+	if (!valid_phys_addr_range(p, count))
 		return -EFAULT;
 	read = 0;
 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
@@ -177,7 +171,7 @@
 	unsigned long copied;
 	void *ptr;
 
-	if (!valid_phys_addr_range(p, &count))
+	if (!valid_phys_addr_range(p, count))
 		return -EFAULT;
 
 	written = 0;
@@ -249,7 +243,7 @@
 {
 	size_t size = vma->vm_end - vma->vm_start;
 
-	if (!valid_mmap_phys_addr_range(vma->vm_pgoff << PAGE_SHIFT, &size))
+	if (!valid_mmap_phys_addr_range(vma->vm_pgoff << PAGE_SHIFT, size))
 		return -EINVAL;
 
 	vma->vm_page_prot = phys_mem_access_prot(file, vma->vm_pgoff,
diff --git a/include/asm-ia64/io.h b/include/asm-ia64/io.h
index 0d9bcc3..acba019 100644
--- a/include/asm-ia64/io.h
+++ b/include/asm-ia64/io.h
@@ -88,8 +88,8 @@
 }
 
 #define ARCH_HAS_VALID_PHYS_ADDR_RANGE
-extern int valid_phys_addr_range (unsigned long addr, size_t *count); /* efi.c */
-extern int valid_mmap_phys_addr_range (unsigned long addr, size_t *count);
+extern int valid_phys_addr_range (unsigned long addr, size_t count); /* efi.c */
+extern int valid_mmap_phys_addr_range (unsigned long addr, size_t count);
 
 /*
  * The following two macros are deprecated and scheduled for removal.
diff --git a/include/linux/efi.h b/include/linux/efi.h
index c7c5dd3..d157254 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -292,6 +292,8 @@
 extern u64 efi_get_iobase (void);
 extern u32 efi_mem_type (unsigned long phys_addr);
 extern u64 efi_mem_attributes (unsigned long phys_addr);
+extern int efi_mem_attribute_range (unsigned long phys_addr, unsigned long size,
+				    u64 attr);
 extern int __init efi_uart_console_only (void);
 extern void efi_initialize_iomem_resources(struct resource *code_resource,
 					struct resource *data_resource);