[Qemu-devel] [PATCH] hw/core/null-machine: Add the possibility to instantiate a CPU, RAM and kernel

[Thomas Huth <thuth@redhat.com>]

Sometimes it is useful to have just a machine with CPU and RAM, without
any further hardware in it, e.g. if you just want to do some instruction
debugging for TCG with a remote GDB attached to QEMU, or run some embedded
code with the "-semihosting" QEMU parameter. qemu-system-m68k already
features a "dummy" machine, and xtensa a "sim" machine for exactly this
purpose.
All target architectures have nowadays also a "none" machine, which would
be a perfect match for this, too - but it currently does not allow to add
CPU, RAM or a kernel yet. Thus let's add these possibilities in a generic
way to the "none" machine, too, so that we hopefully do not need additional
"dummy" machines in the future anymore (and maybe can also get rid of the
already existing "dummy"/"sim" machines one day).
Note that the default behaviour of the "none" machine is not changed, i.e.
no CPU and no RAM is instantiated by default. You've explicitely got to
specify the CPU model with "-cpu" and the amount of RAM with "-m" to get
these new features.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 hw/core/Makefile.objs  |  2 +-
 hw/core/null-machine.c | 81 +++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 81 insertions(+), 2 deletions(-)

diff --git a/hw/core/Makefile.objs b/hw/core/Makefile.objs
index a4c94e5..0b6c0f1 100644
--- a/hw/core/Makefile.objs
+++ b/hw/core/Makefile.objs
@@ -12,7 +12,6 @@ common-obj-$(CONFIG_XILINX_AXI) += stream.o
 common-obj-$(CONFIG_PTIMER) += ptimer.o
 common-obj-$(CONFIG_SOFTMMU) += sysbus.o
 common-obj-$(CONFIG_SOFTMMU) += machine.o
-common-obj-$(CONFIG_SOFTMMU) += null-machine.o
 common-obj-$(CONFIG_SOFTMMU) += loader.o
 common-obj-$(CONFIG_SOFTMMU) += qdev-properties-system.o
 common-obj-$(CONFIG_SOFTMMU) += register.o
@@ -20,3 +19,4 @@ common-obj-$(CONFIG_SOFTMMU) += or-irq.o
 common-obj-$(CONFIG_PLATFORM_BUS) += platform-bus.o
 
 obj-$(CONFIG_SOFTMMU) += generic-loader.o
+obj-$(CONFIG_SOFTMMU) += null-machine.o
diff --git a/hw/core/null-machine.c b/hw/core/null-machine.c
index 0351ba7..b2468ed 100644
--- a/hw/core/null-machine.c
+++ b/hw/core/null-machine.c
@@ -13,18 +13,97 @@
 
 #include "qemu/osdep.h"
 #include "qemu-common.h"
+#include "qemu/error-report.h"
 #include "hw/hw.h"
 #include "hw/boards.h"
+#include "hw/loader.h"
+#include "sysemu/sysemu.h"
+#include "exec/address-spaces.h"
+#include "cpu.h"
+#include "elf.h"
+
+#ifdef TARGET_WORDS_BIGENDIAN
+#define LOAD_ELF_ENDIAN_FLAG 1
+#else
+#define LOAD_ELF_ENDIAN_FLAG 0
+#endif
+
+static hwaddr cpu_initial_pc;
+
+static uint64_t translate_phys_addr(void *opaque, uint64_t addr)
+{
+    return cpu_get_phys_page_debug(CPU(opaque), addr);
+}
+
+static void machine_none_load_kernel(CPUState *cpu, const char *kernel_fname,
+                                     ram_addr_t ram_size)
+{
+    uint64_t elf_entry;
+    int kernel_size;
+
+    if (!ram_size) {
+        error_report("You need RAM for loading a kernel");
+        return;
+    }
+
+    kernel_size = load_elf(kernel_fname, translate_phys_addr, cpu, &elf_entry,
+                           NULL, NULL, LOAD_ELF_ENDIAN_FLAG, EM_NONE, 0, 0);
+    cpu_initial_pc = elf_entry;
+    if (kernel_size < 0) {
+        kernel_size = load_uimage(kernel_fname, &cpu_initial_pc, NULL, NULL,
+                                  NULL, NULL);
+    }
+    if (kernel_size < 0) {
+        kernel_size = load_image_targphys(kernel_fname, 0, ram_size);
+    }
+    if (kernel_size < 0) {
+        error_report("Could not load kernel '%s'", kernel_fname);
+        return;
+    }
+}
+
+static void machine_none_cpu_reset(void *opaque)
+{
+    CPUState *cpu = CPU(opaque);
+
+    cpu_reset(cpu);
+    cpu_set_pc(cpu, cpu_initial_pc);
+}
 
 static void machine_none_init(MachineState *machine)
 {
+    ram_addr_t ram_size = machine->ram_size;
+    MemoryRegion *ram;
+    CPUState *cpu = NULL;
+
+    /* Initialize CPU (if a model has been specified) */
+    if (machine->cpu_model) {
+        cpu = cpu_init(machine->cpu_model);
+        if (!cpu) {
+            error_report("Unable to initialize CPU");
+            exit(1);
+        }
+        qemu_register_reset(machine_none_cpu_reset, cpu);
+        cpu_reset(cpu);
+    }
+
+    /* RAM at address zero */
+    if (ram_size) {
+        ram = g_new(MemoryRegion, 1);
+        memory_region_allocate_system_memory(ram, NULL, "ram", ram_size);
+        memory_region_add_subregion(get_system_memory(), 0, ram);
+    }
+
+    if (machine->kernel_filename) {
+        machine_none_load_kernel(cpu, machine->kernel_filename, ram_size);
+    }
 }
 
 static void machine_none_machine_init(MachineClass *mc)
 {
     mc->desc = "empty machine";
     mc->init = machine_none_init;
-    mc->max_cpus = 0;
+    mc->default_ram_size = 0;
 }
 
 DEFINE_MACHINE("none", machine_none_machine_init)
-- 
1.8.3.1