Re: [Qemu-arm] [PATCH] debugcon: Add -debugport option to allow changing debug console port number

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Aug 05, 2016 at 06:19:39PM +0800, Lv Zheng wrote:
> Changing debugcon port to 0x402 allows the seabios AML table pre-defined
> DBUG() control method to be able to dump the AML debugging information to
> the re-directed debugging console.
> 
> If the debug port number is configurable, users can further specify a
> proper IO port number for it to make external BIOS's debugging
> facility functioning.
> 
> Signed-off-by: Lv Zheng <lv.zheng@intel.com>

This doesn't look like a reasonable interface.

How will user know which io ports are safe to use,
to avoid e.g. conflicts with pci devices?



> ---
>  hw/char/debugcon.c      |    4 ++++
>  hw/i386/acpi-build.c    |    3 ++-
>  include/sysemu/sysemu.h |    1 +
>  qemu-options.hx         |    9 +++++++++
>  vl.c                    |   15 +++++++++++++++
>  5 files changed, 31 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/char/debugcon.c b/hw/char/debugcon.c
> index e7f025e..f966a09 100644
> --- a/hw/char/debugcon.c
> +++ b/hw/char/debugcon.c
> @@ -105,6 +105,10 @@ static void debugcon_isa_realizefn(DeviceState *dev, Error **errp)
>          error_propagate(errp, err);
>          return;
>      }
> +    if (debug_port != 0xe9) {
> +        qdev_prop_set_uint32(dev, "iobase", debug_port);
> +        qdev_prop_set_uint32(dev, "readback", debug_port);
> +    }
>      memory_region_init_io(&s->io, OBJECT(dev), &debugcon_ops, s,
>                            TYPE_ISA_DEBUGCON_DEVICE, 1);
>      memory_region_add_subregion(isa_address_space_io(d),
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index a26a4bb..14c6224 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -1442,7 +1442,8 @@ static void build_dbg_aml(Aml *table)
>      Aml *idx = aml_local(2);
>  
>      aml_append(scope,
> -       aml_operation_region("DBG", AML_SYSTEM_IO, aml_int(0x0402), 0x01));
> +       aml_operation_region("DBG", AML_SYSTEM_IO,
> +                            aml_int(debug_port), 0x01));
>      field = aml_field("DBG", AML_BYTE_ACC, AML_NOLOCK, AML_PRESERVE);
>      aml_append(field, aml_named_field("DBGB", 8));
>      aml_append(scope, field);
> diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
> index ee7c760..9e0a30b 100644
> --- a/include/sysemu/sysemu.h
> +++ b/include/sysemu/sysemu.h
> @@ -167,6 +167,7 @@ extern uint8_t qemu_extra_params_fw[2];
>  extern QEMUClockType rtc_clock;
>  extern const char *mem_path;
>  extern int mem_prealloc;
> +extern uint32_t debug_port;
>  
>  #define MAX_NODES 128
>  #define NUMA_NODE_UNASSIGNED MAX_NODES
> diff --git a/qemu-options.hx b/qemu-options.hx
> index a71aaf8..05aedce 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -3123,6 +3123,15 @@ The default device is @code{vc} in graphical mode and @code{stdio} in
>  non graphical mode.
>  ETEXI
>  
> +DEF("debugport", HAS_ARG, QEMU_OPTION_debugport, \
> +    "-debugport n     Specify debug IO port number\n",
> +    QEMU_ARCH_ALL)
> +STEXI
> +@item -debugport @var{n}
> +@findex -debugport
> +Specify the debug IO port number, default is 0xe9.
> +ETEXI
> +
>  DEF("pidfile", HAS_ARG, QEMU_OPTION_pidfile, \
>      "-pidfile file   write PID to 'file'\n", QEMU_ARCH_ALL)
>  STEXI
> diff --git a/vl.c b/vl.c
> index e7c2c62..710e14d 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -178,6 +178,7 @@ bool boot_strict;
>  uint8_t *boot_splash_filedata;
>  size_t boot_splash_filedata_size;
>  uint8_t qemu_extra_params_fw[2];
> +uint32_t debug_port = 0xe9;
>  
>  int icount_align_option;
>  
> @@ -2584,6 +2585,17 @@ static int debugcon_parse(const char *devname)
>      return 0;
>  }
>  
> +static void debugcon_parse_port(const char *arg)
> +{
> +    uint32_t port;
> +
> +    port = strtoul(arg, NULL, 0);
> +    if (port) {
> +        printf("Re-assign debug console to port 0x%08x.\n", port);
> +        debug_port = port;
> +    }
> +}
> +
>  static gint machine_class_cmp(gconstpointer a, gconstpointer b)
>  {
>      const MachineClass *mc1 = a, *mc2 = b;
> @@ -3580,6 +3592,9 @@ int main(int argc, char **argv, char **envp)
>              case QEMU_OPTION_debugcon:
>                  add_device_config(DEV_DEBUGCON, optarg);
>                  break;
> +            case QEMU_OPTION_debugport:
> +                debugcon_parse_port(optarg);
> +                break;
>              case QEMU_OPTION_loadvm:
>                  loadvm = optarg;
>                  break;
> -- 
> 1.7.10