Re: [PATCH v4 08/14] none-machine: add 'ram-addr' property

[Philippe Mathieu-Daudé]

On 23/2/22 10:07, Damien Hedde wrote:

Add the property to configure a the base address of the ram.
The default value remains zero.

This commit is needed to use the 'none' machine as a base, and
subsequently to dynamically populate it using qapi commands. Having
a non null 'ram' is really hard to workaround because of the actual
constraints on the generic loader: it prevents loading binaries
bigger than ram_size (with a null ram, we cannot load anything).
For now we need to be able to use the existing ram creation
feature of the none machine with a configurable base address.

Signed-off-by: Damien Hedde <damien.he...@greensocs.com>
---
  hw/core/null-machine.c | 34 ++++++++++++++++++++++++++++++++--
  1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/hw/core/null-machine.c b/hw/core/null-machine.c
index 7eb258af07..5fd1cc0218 100644
--- a/hw/core/null-machine.c
+++ b/hw/core/null-machine.c
@@ -16,9 +16,11 @@
  #include "hw/boards.h"
  #include "exec/address-spaces.h"
  #include "hw/core/cpu.h"
+#include "qapi/visitor.h"

struct NoneMachineState {

      MachineState parent;
+    uint64_t ram_addr;
  };

#define TYPE_NONE_MACHINE MACHINE_TYPE_NAME("none")

@@ -26,6 +28,7 @@ OBJECT_DECLARE_SIMPLE_TYPE(NoneMachineState, NONE_MACHINE)

static void machine_none_init(MachineState *mch)

  {
+    NoneMachineState *nms = NONE_MACHINE(mch);
      CPUState *cpu = NULL;

/* Initialize CPU (if user asked for it) */

@@ -37,9 +40,13 @@ static void machine_none_init(MachineState *mch)
          }
      }

- /* RAM at address zero */

+    /* RAM at configured address (default: 0) */
      if (mch->ram) {
-        memory_region_add_subregion(get_system_memory(), 0, mch->ram);
+        memory_region_add_subregion(get_system_memory(), nms->ram_addr,
+                                    mch->ram);
+    } else if (nms->ram_addr) {
+        error_report("'ram-addr' has been specified but the size is zero");

I'm not sure about this error message, IIUC we can get here if no ram
backend is provided, not if we have one zero-sized. Otherwise LGTM.

+        exit(1);
      }