[PATCH RFCv2 4/6] s390x: prepare device memory address space

[David Hildenbrand]

Let's allocate the device memory information and setup the device
memory address space. Expose the maximum ramsize via diag260. The RAM
size returned via SCLP is not modified. Guest OSs which support
virtio-mem are expected to consult diag260.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 hw/s390x/s390-virtio-ccw.c         | 43 ++++++++++++++++++++++++++++++
 hw/s390x/sclp.c                    |  3 ++-
 include/hw/s390x/s390-virtio-ccw.h |  3 +++
 target/s390x/diag.c                | 10 +++++--
 4 files changed, 56 insertions(+), 3 deletions(-)

diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index 2e6d292c23..577590e623 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -160,6 +160,35 @@ static void virtio_ccw_register_hcalls(void)
                                    virtio_ccw_hcall_early_printk);
 }
 
+static void s390_device_memory_init(MachineState *machine)
+{
+    MemoryRegion *sysmem = get_system_memory();
+
+    machine->device_memory = g_malloc0(sizeof(*machine->device_memory));
+
+    /* initialize device memory address space */
+    if (machine->ram_size < machine->maxram_size) {
+        ram_addr_t device_mem_size = machine->maxram_size - machine->ram_size;
+
+        if (QEMU_ALIGN_UP(machine->maxram_size, MiB) != machine->maxram_size) {
+            error_report("maximum memory size must by aligned to 1 MB");
+            exit(EXIT_FAILURE);
+        }
+
+        machine->device_memory->base = machine->ram_size;
+        if (machine->device_memory->base + device_mem_size < device_mem_size) {
+            error_report("unsupported amount of maximum memory: " RAM_ADDR_FMT,
+                         machine->maxram_size);
+            exit(EXIT_FAILURE);
+        }
+
+        memory_region_init(&machine->device_memory->mr, OBJECT(machine),
+                           "device-memory", device_mem_size);
+        memory_region_add_subregion(sysmem, machine->device_memory->base,
+                                    &machine->device_memory->mr);
+    }
+}
+
 static void s390_memory_init(MachineState *machine)
 {
     MemoryRegion *sysmem = get_system_memory();
@@ -194,6 +223,11 @@ static void s390_memory_init(MachineState *machine)
     s390_skeys_init();
     /* Initialize storage attributes device */
     s390_stattrib_init();
+
+    /* Support for memory devices is glued to compat machines. */
+    if (memory_devices_allowed()) {
+        s390_device_memory_init(machine);
+    }
 }
 
 static void s390_init_ipl_dev(const char *kernel_filename,
@@ -617,6 +651,7 @@ static void ccw_machine_class_init(ObjectClass *oc, void 
*data)
     s390mc->cpu_model_allowed = true;
     s390mc->css_migration_enabled = true;
     s390mc->hpage_1m_allowed = true;
+    s390mc->memory_devices_allowed = true;
     mc->init = ccw_init;
     mc->reset = s390_machine_reset;
     mc->hot_add_cpu = s390_hot_add_cpu;
@@ -713,6 +748,11 @@ bool hpage_1m_allowed(void)
     return get_machine_class()->hpage_1m_allowed;
 }
 
+bool memory_devices_allowed(void)
+{
+    return get_machine_class()->memory_devices_allowed;
+}
+
 static char *machine_get_loadparm(Object *obj, Error **errp)
 {
     S390CcwMachineState *ms = S390_CCW_MACHINE(obj);
@@ -831,8 +871,11 @@ static void ccw_machine_5_0_instance_options(MachineState 
*machine)
 
 static void ccw_machine_5_0_class_options(MachineClass *mc)
 {
+    S390CcwMachineClass *s390mc = S390_MACHINE_CLASS(mc);
+
     ccw_machine_5_1_class_options(mc);
     compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len);
+    s390mc->memory_devices_allowed = false;
 }
 DEFINE_CCW_MACHINE(5_0, "5.0", false);
 
diff --git a/hw/s390x/sclp.c b/hw/s390x/sclp.c
index f59195e15a..972995d928 100644
--- a/hw/s390x/sclp.c
+++ b/hw/s390x/sclp.c
@@ -22,6 +22,7 @@
 #include "hw/s390x/event-facility.h"
 #include "hw/s390x/s390-pci-bus.h"
 #include "hw/s390x/ipl.h"
+#include "hw/s390x/s390-virtio-ccw.h"
 
 static inline SCLPDevice *get_sclp_device(void)
 {
@@ -110,7 +111,7 @@ static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb)
         read_info->rnsize2 = cpu_to_be32(rnsize);
     }
 
-    /* we don't support standby memory, maxram_size is never exposed */
+    /* We don't support standby memory, maxram_size is exposed via diag260. */
     rnmax = machine->ram_size >> sclp->increment_size;
     if (rnmax < 0x10000) {
         read_info->rnmax = cpu_to_be16(rnmax);
diff --git a/include/hw/s390x/s390-virtio-ccw.h 
b/include/hw/s390x/s390-virtio-ccw.h
index cd1dccc6e3..efbd9f1da1 100644
--- a/include/hw/s390x/s390-virtio-ccw.h
+++ b/include/hw/s390x/s390-virtio-ccw.h
@@ -41,6 +41,7 @@ typedef struct S390CcwMachineClass {
     bool cpu_model_allowed;
     bool css_migration_enabled;
     bool hpage_1m_allowed;
+    bool memory_devices_allowed;
 } S390CcwMachineClass;
 
 /* runtime-instrumentation allowed by the machine */
@@ -49,6 +50,8 @@ bool ri_allowed(void);
 bool cpu_model_allowed(void);
 /* 1M huge page mappings allowed by the machine */
 bool hpage_1m_allowed(void);
+/* Allow memory devices are allowed (memory device address space created). */
+bool memory_devices_allowed(void);
 
 /**
  * Returns true if (vmstate based) migration of the channel subsystem
diff --git a/target/s390x/diag.c b/target/s390x/diag.c
index 5378fcf582..9abd23b64a 100644
--- a/target/s390x/diag.c
+++ b/target/s390x/diag.c
@@ -27,14 +27,20 @@ void handle_diag_260(CPUS390XState *env, uint64_t r1, 
uint64_t r3, uintptr_t ra)
 {
     MachineState *ms = MACHINE(qdev_get_machine());
     const ram_addr_t initial_ram_size = ms->ram_size;
+    const ram_addr_t maximum_ram_size = ms->maxram_size;
     const uint64_t subcode = env->regs[r3];
 
     switch (subcode) {
     case 0xc:
         /* The first storage extent maps to our initial ram. */
         env->regs[r1] = initial_ram_size - 1;
-        /* The highest addressable byte maps to the initial ram size for now. 
*/
-        env->regs[r3] = initial_ram_size - 1;
+        if (memory_devices_allowed()) {
+            /* The highest addressable byte maps to the maximum ram size. */
+            env->regs[r3] = maximum_ram_size - 1;
+        } else {
+            /* The highest addressable byte maps to the initial ram size. */
+            env->regs[r3] = initial_ram_size - 1;
+        }
         break;
     case 0x10: {
         ram_addr_t addr, length;
-- 
2.26.2