[S390] System z large page support.

This adds hugetlbfs support on System z, using both hardware large page
support if available and software large page emulation on older hardware.
Shared (large) page tables are implemented in software emulation mode,
by using page->index of the first tail page from a compound large page
to store page table information.

Signed-off-by: Gerald Schaefer <geraldsc@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c
index bd188f6bd0e2..d0e09684b9ce 100644
--- a/arch/s390/kernel/early.c
+++ b/arch/s390/kernel/early.c
@@ -268,6 +268,19 @@ static noinline __init void setup_lowcore_early(void)
         s390_base_pgm_handler_fn = early_pgm_check_handler;
 }
 
+static noinline __init void setup_hpage(void)
+{
+#ifndef CONFIG_DEBUG_PAGEALLOC
+        unsigned int facilities;
+
+        facilities = stfl();
+        if (!(facilities & (1UL << 23)) || !(facilities & (1UL << 29)))
+                return;
+        machine_flags |= MACHINE_FLAG_HPAGE;
+        __ctl_set_bit(0, 23);
+#endif
+}
+
 static __init void detect_mvpg(void)
 {
 #ifndef CONFIG_64BIT
@@ -360,6 +373,8 @@ static __init void detect_machine_facilities(void)
         facilities = stfl();
         if (facilities & (1 << 28))
                 machine_flags |= MACHINE_FLAG_IDTE;
+        if (facilities & (1 << 23))
+                machine_flags |= MACHINE_FLAG_PFMF;
         if (facilities & (1 << 4))
                 machine_flags |= MACHINE_FLAG_MVCOS;
 #endif
@@ -388,6 +403,7 @@ void __init startup_init(void)
         detect_diag9c();
         detect_diag44();
         detect_machine_facilities();
+        setup_hpage();
         sclp_read_info_early();
         sclp_facilities_detect();
         memsize = sclp_memory_detect();