[Qemu-devel] [PatchV2] s390x: fix memory detection for guests > 64GB

[Christian Borntraeger]

the s390 memory detection has a 16bit field that specifies the amount of
increments. This patch adopts the memory size to always fit into that
scheme. This also fixes virtio detection for these guests, since the 
descriptor page is located after the main memory.

Signed-off-by: Christian Borntraeger <borntrae...@de.ibm.com>

---
 target-s390x/op_helper.c |    8 ++++++--
 vl.c                     |   11 +++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

Index: b/target-s390x/op_helper.c
===================================================================
--- a/target-s390x/op_helper.c
+++ b/target-s390x/op_helper.c
@@ -2361,6 +2361,7 @@ static void ext_interrupt(CPUState *env,
 int sclp_service_call(CPUState *env, uint32_t sccb, uint64_t code)
 {
     int r = 0;
+    int shift = 0;
 
 #ifdef DEBUG_HELPER
     printf("sclp(0x%x, 0x%" PRIx64 ")\n", sccb, code);
@@ -2375,8 +2376,11 @@ int sclp_service_call(CPUState *env, uin
     switch(code) {
         case SCLP_CMDW_READ_SCP_INFO:
         case SCLP_CMDW_READ_SCP_INFO_FORCED:
-            stw_phys(sccb + SCP_MEM_CODE, ram_size >> 20);
-            stb_phys(sccb + SCP_INCREMENT, 1);
+            while ((ram_size >> (20 + shift)) > 65535) {
+                shift++;
+            }
+            stw_phys(sccb + SCP_MEM_CODE, ram_size >> (20 + shift));
+            stb_phys(sccb + SCP_INCREMENT, 1 << shift);
             stw_phys(sccb + SCP_RESPONSE_CODE, 0x10);
 
             if (kvm_enabled()) {
Index: b/vl.c
===================================================================
--- a/vl.c
+++ b/vl.c
@@ -2962,6 +2962,17 @@ int main(int argc, char **argv, char **e
     if (ram_size == 0)
         ram_size = DEFAULT_RAM_SIZE * 1024 * 1024;
 
+    /* s390x ram size detection needs a 16bit multiplier + an increment. So
+       guests > 64GB can be specified in 2MB steps etc */
+    if (strstr(machine->name, "s390")) {
+        int shift = 0;
+
+        while ((ram_size >> (20 + shift)) > 65535) {
+            shift++;
+        }
+        ram_size = ram_size >> (20 + shift) << (20 + shift);
+    }
+
     /* init the dynamic translator */
     cpu_exec_init_all(tb_size * 1024 * 1024);