x86: add gbpages switches
These new controls toggle experimental support for a new CPU feature,
the straightforward extension of largepages from the pmd level to the
pud level, which allows 1GB (kernel) TLBs instead of 2MB TLBs.
Turn it off by default, as this code has not been tested well enough yet.
Use the CONFIG_DIRECT_GBPAGES=y .config option or gbpages on the
boot line can be used to enable it. If enabled in the .config then
nogbpages boot option disables it.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index a02a14f..6e7d5a4 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -54,6 +54,26 @@
DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
+int direct_gbpages __meminitdata
+#ifdef CONFIG_DIRECT_GBPAGES
+ = 1
+#endif
+;
+
+static int __init parse_direct_gbpages_off(char *arg)
+{
+ direct_gbpages = 0;
+ return 0;
+}
+early_param("nogbpages", parse_direct_gbpages_off);
+
+static int __init parse_direct_gbpages_on(char *arg)
+{
+ direct_gbpages = 1;
+ return 0;
+}
+early_param("gbpages", parse_direct_gbpages_on);
+
/*
* NOTE: pagetable_init alloc all the fixmap pagetables contiguous on the
* physical space so we can cache the place of the first one and move