Re: [PATCH v2 1/2] nubus-device: round Declaration ROM memory region address to qemu_target_page_size()

[Philippe Mathieu-Daudé]

On 8/1/24 20:20, Mark Cave-Ayland wrote:

Declaration ROM binary images can be any arbitrary size, however if a host ROM
memory region is not aligned to qemu_target_page_size() then we fail the
"assert(!(iotlb & ~TARGET_PAGE_MASK))" check in tlb_set_page_full().

Ensure that the host ROM memory region is aligned to qemu_target_page_size()
and adjust the offset at which the Declaration ROM image is loaded, since Nubus
ROM images are unusual in that they are aligned to the end of the slot address
space.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayl...@ilande.co.uk>
---
  hw/nubus/nubus-device.c | 16 ++++++++++++----
  1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/hw/nubus/nubus-device.c b/hw/nubus/nubus-device.c
index 49008e4938..e4f824d58b 100644
--- a/hw/nubus/nubus-device.c
+++ b/hw/nubus/nubus-device.c
@@ -10,6 +10,7 @@

#include "qemu/osdep.h"

  #include "qemu/datadir.h"
+#include "exec/target_page.h"
  #include "hw/irq.h"
  #include "hw/loader.h"
  #include "hw/nubus/nubus.h"
@@ -30,7 +31,7 @@ static void nubus_device_realize(DeviceState *dev, Error 
**errp)
      NubusDevice *nd = NUBUS_DEVICE(dev);
      char *name, *path;
      hwaddr slot_offset;
-    int64_t size;
+    int64_t size, align_size;

Both are 'size_t'.

      int ret;

/* Super */

@@ -76,16 +77,23 @@ static void nubus_device_realize(DeviceState *dev, Error 
**errp)
          }

name = g_strdup_printf("nubus-slot-%x-declaration-rom", nd->slot);

-        memory_region_init_rom(&nd->decl_rom, OBJECT(dev), name, size,
+
+        /*
+         * Ensure ROM memory region is aligned to target page size regardless
+         * of the size of the Declaration ROM image
+         */
+        align_size = ROUND_UP(size, qemu_target_page_size());
+        memory_region_init_rom(&nd->decl_rom, OBJECT(dev), name, align_size,
                                 &error_abort);
-        ret = load_image_mr(path, &nd->decl_rom);
+        ret = load_image_size(path, memory_region_get_ram_ptr(&nd->decl_rom) +
+                                    (uintptr_t)align_size - size, size);

memory_region_get_ram_ptr() returns a 'void *' so this looks dubious.
Maybe use a local variable to ease offset calculation?

  char *rombase = memory_region_get_ram_ptr(&nd->decl_rom);
  ret = load_image_size(path, rombase + align_size - size, size);

Otherwise KISS but ugly:

  ret = load_image_size(path,
            (void *)((uintptr_t)memory_region_get_ram_ptr(&nd->decl_rom)
                     + align_size - size), size);

          g_free(path);
          g_free(name);
          if (ret < 0) {
              error_setg(errp, "could not load romfile \"%s\"", nd->romfile);
              return;
          }
-        memory_region_add_subregion(&nd->slot_mem, NUBUS_SLOT_SIZE - size,
+        memory_region_add_subregion(&nd->slot_mem, NUBUS_SLOT_SIZE - 
align_size,
                                      &nd->decl_rom);
      }
  }