xen_arm: Initialize RAM and add hi/low memory regions

In order to use virtio backends we need to initialize RAM for the
xen-mapcache (which is responsible for mapping guest memory using foreign
mapping) to work. Calculate and add hi/low memory regions based on
machine->ram_size.

Use the constants defined in public header arch-arm.h to be aligned with the xen
toolstack.

While using this machine, the toolstack should then pass real ram_size using
"-m" arg. If "-m" is not given, create a QEMU machine without IOREQ and other
emulated devices like TPM and VIRTIO. This is done to keep this QEMU machine
usable for /etc/init.d/xencommons.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Signed-off-by: Vikram Garhwal <vikram.garhwal@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

hw/arm/xen_arm.c

@@ -60,6 +60,8 @@ struct XenArmState {
     } cfg;
 };
 
+static MemoryRegion ram_lo, ram_hi;
+
 /*
  * VIRTIO_MMIO_DEV_SIZE is imported from tools/libs/light/libxl_arm.c under Xen
  * repository.
@@ -92,6 +94,39 @@ static void xen_create_virtio_mmio_devices(XenArmState *xam)
     }
 }
 
+static void xen_init_ram(MachineState *machine)
+{
+    MemoryRegion *sysmem = get_system_memory();
+    ram_addr_t block_len, ram_size[GUEST_RAM_BANKS];
+
+    if (machine->ram_size <= GUEST_RAM0_SIZE) {
+        ram_size[0] = machine->ram_size;
+        ram_size[1] = 0;
+        block_len = GUEST_RAM0_BASE + ram_size[0];
+    } else {
+        ram_size[0] = GUEST_RAM0_SIZE;
+        ram_size[1] = machine->ram_size - GUEST_RAM0_SIZE;
+        block_len = GUEST_RAM1_BASE + ram_size[1];
+    }
+
+    memory_region_init_ram(&ram_memory, NULL, "xen.ram", block_len,
+                           &error_fatal);
+
+    memory_region_init_alias(&ram_lo, NULL, "xen.ram.lo", &ram_memory,
+                             GUEST_RAM0_BASE, ram_size[0]);
+    memory_region_add_subregion(sysmem, GUEST_RAM0_BASE, &ram_lo);
+    DPRINTF("Initialized region xen.ram.lo: base 0x%llx size 0x%lx\n",
+            GUEST_RAM0_BASE, ram_size[0]);
+
+    if (ram_size[1] > 0) {
+        memory_region_init_alias(&ram_hi, NULL, "xen.ram.hi", &ram_memory,
+                                 GUEST_RAM1_BASE, ram_size[1]);
+        memory_region_add_subregion(sysmem, GUEST_RAM1_BASE, &ram_hi);
+        DPRINTF("Initialized region xen.ram.hi: base 0x%llx size 0x%lx\n",
+                GUEST_RAM1_BASE, ram_size[1]);
+    }
+}
+
 void arch_handle_ioreq(XenIOState *state, ioreq_t *req)
 {
     hw_error("Invalid ioreq type 0x%x\n", req->type);
@@ -141,6 +176,14 @@ static void xen_arm_init(MachineState *machine)
 
     xam->state =  g_new0(XenIOState, 1);
 
+    if (machine->ram_size == 0) {
+        DPRINTF("ram_size not specified. QEMU machine started without IOREQ"
+                "(no emulated devices including Virtio)\n");
+        return;
+    }
+
+    xen_init_ram(machine);
+
     xen_register_ioreq(xam->state, machine->smp.cpus, xen_memory_listener);
 
     xen_create_virtio_mmio_devices(xam);
@@ -188,6 +231,8 @@ static void xen_arm_machine_class_init(ObjectClass *oc, void *data)
     mc->init = xen_arm_init;
     mc->max_cpus = 1;
     mc->default_machine_opts = "accel=xen";
+    /* Set explicitly here to make sure that real ram_size is passed */
+    mc->default_ram_size = 0;
 
 #ifdef CONFIG_TPM
     object_class_property_add(oc, "tpm-base-addr", "uint64_t",