Re: [Qemu-devel] [PATCH 4/4] QemuOpts: command line switches for the config file.

[Nathan Baum <nathan@parenthephobia.org.uk>]

On Wed, 2009-10-14 at 10:39 +0200, Gerd Hoffmann wrote:
> Adds -readconfig and -writeconfig command line switches to read/write
> QemuOpts from config file.
> 
> In theory you should be able to do:
> 
>   qemu < machine config cmd line switches here > -writeconfig vm.cfg
>   qemu -readconfig vm.cfg
> 
> In practice it will not work.  Not all command line switches are
> converted to QemuOpts, so you'll have to keep the not-yet converted ones
> on the second line.  Also there might be bugs lurking which prevent even
> the converted ones from working correctly.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  qemu-options.hx |    5 +++++
>  vl.c            |   30 ++++++++++++++++++++++++++++++
>  2 files changed, 35 insertions(+), 0 deletions(-)
> 
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 3dd76b3..6cbf9e2 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -1682,3 +1682,8 @@ DEF("semihosting", 0, QEMU_OPTION_semihosting,
>  DEF("old-param", 0, QEMU_OPTION_old_param,
>      "-old-param      old param mode\n")
>  #endif
> +DEF("readconfig", HAS_ARG, QEMU_OPTION_readconfig,
> +    "-readconfig <file>\n")
> +DEF("writeconfig", HAS_ARG, QEMU_OPTION_writeconfig,
> +    "-writeconfig <file>\n"
> +    "                read/write config file")
> diff --git a/vl.c b/vl.c
> index afe01af..ad902fe 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -5513,6 +5513,36 @@ int main(int argc, char **argv, char **envp)
>                  xen_mode = XEN_ATTACH;
>                  break;
>  #endif
> +            case QEMU_OPTION_readconfig:
> +                {
> +                    FILE *fp;
> +                    fp = fopen(optarg, "r");
> +                    if (fp == NULL) {
> +                        fprintf(stderr, "open %s: %s\n", optarg, strerror(errno));
> +                        exit(1);
> +                    }
> +                    if (qemu_config_parse(fp) != 0) {
> +                        exit(1);
> +                    }
> +                    fclose(fp);
> +                    break;
> +                }
> +            case QEMU_OPTION_writeconfig:
> +                {
> +                    FILE *fp;
> +                    if (strcmp(optarg, "-") == 0) {
> +                        fp = stdout;
> +                    } else {
> +                        fp = fopen(optarg, "w");
> +                        if (fp == NULL) {
> +                            fprintf(stderr, "open %s: %s\n", optarg, strerror(errno));
> +                            exit(1);
> +                        }
> +                    }
> +                    qemu_config_write(fp);
> +                    fclose(fp);
> +                    break;
> +                }
>              }
>          }
>      }


It seems like the typical use-case for -writeconfig will be for
"upgrading" to the config file system. Might it be more useful for qemu
to exit after writing the config?

Signed-off-by: Nathan Baum <nathan@parenthephobia.org.uk>
--- a/vl.c
+++ b/vl.c
@@ -5546,7 +5546,7 @@ int main(int argc, char **argv, char **envp)
                     }
                     qemu_config_write(fp);
                     fclose(fp);
-                    break;
+                    exit(0);
                 }
             }
         }