[S390] Use diag260 for memory size detection.

Avoid the tprot loop if diag260 works and reports that there are no
holes in memory. The tprot instruction can lead to a significant delay
in the ipl process if the virtual guest has a lot of memory and the
host is under memory pressure.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 15 insertions, 2 deletions

diff --git a/arch/s390/kernel/head64.S b/arch/s390/kernel/head64.S
index 42f54d482441..cc6dbc57eb90 100644
--- a/arch/s390/kernel/head64.S
+++ b/arch/s390/kernel/head64.S
@@ -70,7 +70,22 @@ startup_continue:
         sgr     %r5,%r5                 # set src,length and pad to zero
         mvcle   %r2,%r4,0               # clear mem
         jo      .-4                     # branch back, if not finish
+                                        # set program check new psw mask
+        mvc     __LC_PGM_NEW_PSW(8),.Lpcmsk-.LPG1(%r13)
+        larl    %r1,.Lslowmemdetect     # set program check address
+        stg     %r1,__LC_PGM_NEW_PSW+8
+        lghi    %r1,0xc
+        diag    %r0,%r1,0x260           # get memory size of virtual machine
+        cgr     %r0,%r1                 # different? -> old detection routine
+        jne     .Lslowmemdetect
+        aghi    %r1,1                   # size is one more than end
+        larl    %r2,memory_chunk
+        stg     %r1,8(%r2)              # store size of chunk
+        larl    %r2,memory_size
+        stg     %r1,0(%r2)              # set memory size
+        j       .Ldonemem
 
+.Lslowmemdetect:
         l       %r2,.Lrcp-.LPG1(%r13)   # Read SCP forced command word
 .Lservicecall:
         stosm   .Lpmask-.LPG1(%r13),0x01        # authorize ext interrupts
@@ -139,8 +154,6 @@ startup_continue:
         .int    0x100000
 
 .Lfchunk:
-                                        # set program check new psw mask
-        mvc     __LC_PGM_NEW_PSW(8),.Lpcmsk-.LPG1(%r13)
 
 #
 # find memory chunks.