x86/mm: sparse warning fix for early_memremap

This patch series takes the common bits from the x86 early ioremap
implementation and creates a generic implementation which may be used by
other architectures.  The early ioremap interfaces are intended for
situations where boot code needs to make temporary virtual mappings
before the normal ioremap interfaces are available.  Typically, this
means before paging_init() has run.

This patch (of 6):

There's a lot of sparse warnings for code like below: void *a =
early_memremap(phys_addr, size);

early_memremap intend to map kernel memory with ioremap facility, the
return pointer should be a kernel ram pointer instead of iomem one.

For making the function clearer and supressing sparse warnings this patch
do below two things:
1. cast to (__force void *) for the return value of early_memremap
2. add early_memunmap function and pass (__force void __iomem *) to iounmap

From Boris:
  "Ingo told me yesterday, it makes sense too.  I'd guess we can try it.
   FWIW, all callers of early_memremap use the memory they get remapped
   as normal memory so we should be safe"
Signed-off-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Mark Salter <msalter@redhat.com>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Cc: Borislav Petkov <borislav.petkov@amd.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/include/asm/io.h

@@ -325,9 +325,10 @@ extern void early_ioremap_init(void);
 extern void early_ioremap_reset(void);
 extern void __iomem *early_ioremap(resource_size_t phys_addr,
 				   unsigned long size);
-extern void __iomem *early_memremap(resource_size_t phys_addr,
+extern void *early_memremap(resource_size_t phys_addr,
 				    unsigned long size);
 extern void early_iounmap(void __iomem *addr, unsigned long size);
+extern void early_memunmap(void *addr, unsigned long size);
 extern void fixup_early_ioremap(void);
 extern bool is_early_ioremap_ptep(pte_t *ptep);
 

arch/x86/mm/ioremap.c

@@ -562,10 +562,9 @@ early_ioremap(resource_size_t phys_addr, unsigned long size)
 }
 
 /* Remap memory */
-void __init __iomem *
-early_memremap(resource_size_t phys_addr, unsigned long size)
+void __init *early_memremap(resource_size_t phys_addr, unsigned long size)
 {
-	return __early_ioremap(phys_addr, size, PAGE_KERNEL);
+	return (__force void *)__early_ioremap(phys_addr, size, PAGE_KERNEL);
 }
 
 void __init early_iounmap(void __iomem *addr, unsigned long size)
@@ -620,3 +619,8 @@ void __init early_iounmap(void __iomem *addr, unsigned long size)
 	}
 	prev_map[slot] = NULL;
 }
+
+void __init early_memunmap(void *addr, unsigned long size)
+{
+	early_iounmap((__force void __iomem *)addr, size);
+}