x86: Make 64 bit use early_res instead of bootmem before slab

Finally we can use early_res to replace bootmem for x86_64 now.

Still can use CONFIG_NO_BOOTMEM to enable it or not.

-v2: fix 32bit compiling about MAX_DMA32_PFN
-v3: folded bug fix from LKML message below

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <4B747239.4070907@kernel.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index eb40925..9543984 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -568,6 +568,19 @@
 	  Enable to debug paravirt_ops internals.  Specifically, BUG if
 	  a paravirt_op is missing when it is called.
 
+config NO_BOOTMEM
+	default y
+	bool "Disable Bootmem code"
+	depends on X86_64
+	---help---
+	  Use early_res directly instead of bootmem before slab is ready.
+		- allocator (buddy) [generic]
+		- early allocator (bootmem) [generic]
+		- very early allocator (reserve_early*()) [x86]
+		- very very early allocator (early brk model) [x86]
+	  So reduce one layer between early allocator to final allocator
+
+
 config MEMTEST
 	bool "Memtest"
 	---help---