x86/mm: Further simplify 1 GB kernel linear mappings handling

Ingo Molnar · Ingo Molnar · commit 10971ab269bb · 2015-03-05T09:23:04.000+01:00
It's a bit pointless to allow Kconfig configuration for 1GB kernel
mappings, it's already hidden behind a 'default y' and CONFIG_EXPERT.

Remove this complication and simplify the code by renaming
CONFIG_ENABLE_DIRECT_GBPAGES to CONFIG_X86_DIRECT_GBPAGES and
document the DEBUG_PAGE_ALLOC and KMEMCHECK quirks.

Cc: Luis R. Rodriguez &lt;mcgrof@suse.com&gt;
Cc: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Cc: Andy Lutomirski &lt;luto@amacapital.net&gt;
Cc: Borislav Petkov &lt;bp@alien8.de&gt;
Cc: Borislav Petkov &lt;bp@suse.de&gt;
Cc: Dave Hansen &lt;dave.hansen@linux.intel.com&gt;
Cc: David Vrabel &lt;david.vrabel@citrix.com&gt;
Cc: Dexuan Cui &lt;decui@microsoft.com&gt;
Cc: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
Cc: H. Peter Anvin &lt;hpa@zytor.com&gt;
Cc: JBeulich@suse.com
Cc: Jan Beulich &lt;JBeulich@suse.com&gt;
Cc: Joonsoo Kim &lt;iamjoonsoo.kim@lge.com&gt;
Cc: Juergen Gross &lt;jgross@suse.com&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Pavel Machek &lt;pavel@ucw.cz&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Tony Lindgren &lt;tony@atomide.com&gt;
Cc: Toshi Kani &lt;toshi.kani@hp.com&gt;
Cc: Vlastimil Babka &lt;vbabka@suse.cz&gt;
Cc: Xishi Qiu &lt;qiuxishi@huawei.com&gt;
Cc: julia.lawall@lip6.fr
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
@@ -1299,22 +1299,14 @@ config ARCH_DMA_ADDR_T_64BIT
 	def_bool y
 	depends on X86_64 || HIGHMEM64G
 
-config ENABLE_DIRECT_GBPAGES
+config X86_DIRECT_GBPAGES
 	def_bool y
 	depends on X86_64 && !DEBUG_PAGEALLOC && !KMEMCHECK
-
-config DIRECT_GBPAGES
-	bool "Enable 1GB pages for kernel pagetables" if EXPERT
-	default y
-	depends on ENABLE_DIRECT_GBPAGES
-	---help---
-	  Enable by default the kernel linear mapping to use 1GB pages on CPUs
-	  that support it. This can improve the kernel's performance a tiny bit
-	  by reducing TLB pressure. If in doubt, say "Y". If you've disabled
-	  option but your platform is capable of handling support for this
-	  you can use the gbpages kernel parameter. Likewise if you've enabled
-	  this but you'd like to force disable this option you can use the
-	  nogbpages kernel parameter.
+	---help---
+	  Certain kernel features effectively disable kernel
+	  linear 1 GB mappings (even if the CPU otherwise
+	  supports them), so don't confuse the user by printing
+	  that we have them enabled.
 
 # Common NUMA Features
 config NUMA
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
@@ -133,15 +133,10 @@ int after_bootmem;
 
 static int page_size_mask;
 
-early_param_on_off("gbpages", "nogbpages",
-		   direct_gbpages, CONFIG_DIRECT_GBPAGES);
+early_param_on_off("gbpages", "nogbpages", direct_gbpages, CONFIG_X86_DIRECT_GBPAGES);
 
 static void __init init_gbpages(void)
 {
-	if (!IS_ENABLED(CONFIG_ENABLE_DIRECT_GBPAGES)) {
-		direct_gbpages = 0;
-		return;
-	}
 	if (direct_gbpages && cpu_has_gbpages) {
 		printk(KERN_INFO "Using GB pages for direct mapping\n");
 		page_size_mask |= 1 << PG_LEVEL_1G;
