Re: [Qemu-devel] [PATCH 1/2] memory: Provide separate handling of unassigned io ports accesses

["Andreas Färber" <afaerber@suse.de>]

Am 03.08.2013 10:31, schrieb Jan Kiszka:
> From: Jan Kiszka <jan.kiszka@siemens.com>
> 
> Accesses to unassigned io ports shall return -1 on read and be ignored
> on write. Ensure these properties via dedicated ops, decoupling us from
> the memory core's handling of unassigned accesses.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
>  exec.c                |    3 ++-
>  include/exec/ioport.h |    2 ++
>  ioport.c              |   16 ++++++++++++++++
>  3 files changed, 20 insertions(+), 1 deletions(-)
> 
> diff --git a/exec.c b/exec.c
> index 3ca9381..9ed598f 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -1820,7 +1820,8 @@ static void memory_map_init(void)
>      address_space_init(&address_space_memory, system_memory, "memory");
>  
>      system_io = g_malloc(sizeof(*system_io));
> -    memory_region_init(system_io, NULL, "io", 65536);
> +    memory_region_init_io(system_io, NULL, &unassigned_io_ops, NULL, "io",
> +                          65536);

It was reported that there may be some machines/PHBs that have
overlapping PIO/MMIO. Unless we use priorities, this ..._io MemoryRegion
will shadow or conflict with any ..._io MemoryRegion added to the memory
address space, wouldn't it?

Regards,
Andreas

>      address_space_init(&address_space_io, system_io, "I/O");
>  
>      memory_listener_register(&core_memory_listener, &address_space_memory);
> diff --git a/include/exec/ioport.h b/include/exec/ioport.h
> index bdd4e96..84f7f85 100644
> --- a/include/exec/ioport.h
> +++ b/include/exec/ioport.h
> @@ -45,6 +45,8 @@ typedef struct MemoryRegionPortio {
>  
>  #define PORTIO_END_OF_LIST() { }
>  
> +extern const MemoryRegionOps unassigned_io_ops;
> +
>  void cpu_outb(pio_addr_t addr, uint8_t val);
>  void cpu_outw(pio_addr_t addr, uint16_t val);
>  void cpu_outl(pio_addr_t addr, uint32_t val);
> diff --git a/ioport.c b/ioport.c
> index 79b7f1a..9765588 100644
> --- a/ioport.c
> +++ b/ioport.c
> @@ -44,6 +44,22 @@ typedef struct MemoryRegionPortioList {
>      MemoryRegionPortio ports[];
>  } MemoryRegionPortioList;
>  
> +static uint64_t unassigned_io_read(void *opaque, hwaddr addr, unsigned size)
> +{
> +    return -1UL;
> +}
> +
> +static void unassigned_io_write(void *opaque, hwaddr addr, uint64_t val,
> +                                unsigned size)
> +{
> +}
> +
> +const MemoryRegionOps unassigned_io_ops = {
> +    .read = unassigned_io_read,
> +    .write = unassigned_io_write,
> +    .endianness = DEVICE_NATIVE_ENDIAN,
> +};
> +
>  void cpu_outb(pio_addr_t addr, uint8_t val)
>  {
>      LOG_IOPORT("outb: %04"FMT_pioaddr" %02"PRIx8"\n", addr, val);
> 


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