x86: add hugepagesz option on 64-bit

Add an hugepagesz=...  option similar to IA64, PPC etc.  to x86-64.

This finally allows to select GB pages for hugetlbfs in x86 now that all
the infrastructure is in place.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 2 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 5e20ccb5a736..d55fd88fd0a9 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -774,8 +774,15 @@ and is between 256 and 4096 characters. It is defined in the file
         hisax=          [HW,ISDN]
                         See Documentation/isdn/README.HiSax.
 
-        hugepages=      [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
-        hugepagesz=     [HW,IA-64,PPC] The size of the HugeTLB pages.
+        hugepages=      [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
+        hugepagesz=     [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
+                        On x86 this option can be specified multiple times
+                        interleaved with hugepages= to reserve huge pages
+                        of different sizes. Valid pages sizes on x86-64
+                        are 2M (when the CPU supports "pse") and 1G (when the
+                        CPU supports the "pdpe1gb" cpuinfo flag)
+                        Note that 1GB pages can only be allocated at boot time
+                        using hugepages= and not freed afterwards.
 
         i8042.direct    [HW] Put keyboard port into non-translated mode
         i8042.dumbkbd   [HW] Pretend that controller can only read data from