Re: [Qemu-devel] [PatchV3] s390x: fix memory detection for guests > 64GB

[Christian Borntraeger <borntraeger@de.ibm.com>]

> I'd definitely prefer that over the change on vl.c :)

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 <borntraeger@de.ibm.com>

---
 hw/s390-virtio.c         |   20 +++++++++++++++-----
 target-s390x/op_helper.c |    8 ++++++--
 2 files changed, 21 insertions(+), 7 deletions(-)

Index: b/hw/s390-virtio.c
===================================================================
--- a/hw/s390-virtio.c
+++ b/hw/s390-virtio.c
@@ -133,7 +133,7 @@ int s390_virtio_hypercall(CPUState *env,
 }
 
 /* PC hardware initialisation */
-static void s390_init(ram_addr_t ram_size,
+static void s390_init(ram_addr_t my_ram_size,
                       const char *boot_device,
                       const char *kernel_filename,
                       const char *kernel_cmdline,
@@ -145,19 +145,29 @@ static void s390_init(ram_addr_t ram_siz
     ram_addr_t kernel_size = 0;
     ram_addr_t initrd_offset;
     ram_addr_t initrd_size = 0;
+    int shift = 0;
     uint8_t *storage_keys;
     int i;
 
+    /* s390x ram size detection needs a 16bit multiplier + an increment. So
+       guests > 64GB can be specified in 2MB steps etc. */
+    while ((my_ram_size >> (20 + shift)) > 65535) {
+        shift++;
+    }
+    my_ram_size = my_ram_size >> (20 + shift) << (20 + shift);
+
+    /* lets propagate the changed ram size into the global variable. */
+    ram_size = my_ram_size;
 
     /* get a BUS */
-    s390_bus = s390_virtio_bus_init(&ram_size);
+    s390_bus = s390_virtio_bus_init(&my_ram_size);
 
     /* allocate RAM */
-    ram_addr = qemu_ram_alloc(NULL, "s390.ram", ram_size);
-    cpu_register_physical_memory(0, ram_size, ram_addr);
+    ram_addr = qemu_ram_alloc(NULL, "s390.ram", my_ram_size);
+    cpu_register_physical_memory(0, my_ram_size, ram_addr);
 
     /* allocate storage keys */
-    storage_keys = qemu_mallocz(ram_size / TARGET_PAGE_SIZE);
+    storage_keys = qemu_mallocz(my_ram_size / TARGET_PAGE_SIZE);
 
     /* init CPUs */
     if (cpu_model == NULL) {
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()) {