[PATCH] s390: memory detection > 32GB

The kernel takes a very long time to boot if the memory size is bigger then
32767 MB.  The memory size is contained in a structure created by an sclp
call.  The kernel accesses the field with a LH instrution which performs a
sign extension of a 16 bit word.  In the case of a memory size with bit 2^15
set this results in a very large value and the memory detection just loops for
a long time.  In addition if more then 64 GB are used on a 64 bit system the
memory size is read from an incorrect storage location.

Use zero-extention to read the 16 bit memory size and the correct offset to
read the 4 byte memory size on 64 bit.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/arch/s390/kernel/head64.S b/arch/s390/kernel/head64.S
index 8366793bc371..8e2caf9dc185 100644
--- a/arch/s390/kernel/head64.S
+++ b/arch/s390/kernel/head64.S
@@ -518,9 +518,9 @@ startup:basr  %r13,0                     # get base
         l     %r2,.Lrcp2-.LPG1(%r13)    # try with Read SCP
         b     .Lservicecall-.LPG1(%r13)
 .Lprocsccb:
-        lh    %r1,.Lscpincr1-PARMAREA(%r4) # use this one if != 0
-        chi   %r1,0x00
-        jne   .Lscnd
+        lghi  %r1,0
+        icm   %r1,3,.Lscpincr1-PARMAREA(%r4) # use this one if != 0
+        jnz   .Lscnd
         lg    %r1,.Lscpincr2-PARMAREA(%r4) # otherwise use this one
 .Lscnd:
         xr    %r3,%r3                   # same logic