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

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

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-ayland@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);
>       }
>   }