Re: [PATCH for-7.1] vl: fix [memory] section with -readconfig

[Markus Armbruster]

Paolo Bonzini <pbonzini@redhat.com> writes:

> The -M memory.* options do not have magic applied to them than the -m
> option, namely no "M" (for mebibytes) is tacked at the end of a
> suffixless value for "-M memory.size".

This sentence is confusing.  Do you mean "like the -m option"?

> This magic is performed by parse_memory_options, and we have to
> do it for both "-m" and the [memory] section of a config file.
> Storing [memory] sections directly to machine_opts_dict changed
> the meaning of
>
>     [memory]
>       size = "1024"
>
> in a -readconfig file from 1024MiB to 8KiB (1024 Bytes rounded up to
> 8KiB silently).  To avoid this, the [memory] section has to be
> changed back to QemuOpts (combining [memory] and "-m" will work fine
> thanks to .merge_lists being true).
>
> Change parse_memory_options() so that, similar to the older function
> set_memory_options(), it operates after command line parsing is done;
> and also call it where set_memory_options() used to be.
>
> Note, the parsing code uses exit(1) instead of exit(EXIT_FAILURE) to
> match neighboring code.

Thanks for that.

> Reported-by: Markus Armbruster <armbru@redhat.com>
> Fixes: ce9d03fb3f ("machine: add mem compound property", 2022-05-12)
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  softmmu/vl.c | 25 ++++++++++++++++---------
>  1 file changed, 16 insertions(+), 9 deletions(-)
>
> diff --git a/softmmu/vl.c b/softmmu/vl.c
> index aabd82e09a..3c23f266e9 100644
> --- a/softmmu/vl.c
> +++ b/softmmu/vl.c
> @@ -1947,17 +1947,20 @@ static void qemu_resolve_machine_memdev(void)
>      }
>  }
>  
> -static void parse_memory_options(const char *arg)
> +static void parse_memory_options(void)
>  {
> -    QemuOpts *opts;
> +    QemuOpts *opts = qemu_find_opts_singleton("memory");
>      QDict *dict, *prop;
>      const char *mem_str;
> +    Location loc;
>  
> -    opts = qemu_opts_parse_noisily(qemu_find_opts("memory"), arg, true);
>      if (!opts) {
> -        exit(EXIT_FAILURE);
> +        return;
>      }

qemu_find_opts_singleton() never returns null.  Drop the null check,
please.

> +    loc_push_none(&loc);
> +    qemu_opts_loc_restore(opts);
> +
>      prop = qdict_new();
>  
>      if (qemu_opt_get_size(opts, "size", 0) != 0) {

This treats "size=0" like absent size.  Before commit ce9d03fb3f, we
instead checked

       mem_str = qemu_opt_get(opts, "size");
       if (mem_str) {

Makes more sense, doesn't it?

Also, with the new check above, the check below...

           mem_str = qemu_opt_get(opts, "size");
           if (!*mem_str) {
               error_report("missing 'size' option value");
               exit(EXIT_FAILURE);
           }

... looks dead.  We get there only when qemu_opt_get_size() returns
non-zero, which implies a non-blank string.

           /* Fix up legacy suffix-less format */
           if (g_ascii_isdigit(mem_str[strlen(mem_str) - 1])) {
               g_autofree char *mib_str = g_strdup_printf("%sM", mem_str);
               qdict_put_str(prop, "size", mib_str);
           } else {
               qdict_put_str(prop, "size", mem_str);
           }
       }

       if (qemu_opt_get(opts, "maxmem")) {
           qdict_put_str(prop, "max-size", qemu_opt_get(opts, "maxmem"));
       }
       if (qemu_opt_get(opts, "slots")) {
           qdict_put_str(prop, "slots", qemu_opt_get(opts, "slots"));
       }

       dict = qdict_new();
> @@ -1987,6 +1990,7 @@ static void parse_memory_options(const char *arg)
>      qdict_put(dict, "memory", prop);
>      keyval_merge(machine_opts_dict, dict, &error_fatal);
>      qobject_unref(dict);
> +    loc_pop(&loc);
>  }
>  
>  static void qemu_create_machine(QDict *qdict)

Commit ce9d03fb3f changed this function's purpose and renamed it from
set_memory_options() to parse_memory_options().

This commit is a partial revert.  It doesn't revert the change of name.
Intentional?

> @@ -2053,8 +2057,7 @@ static bool is_qemuopts_group(const char *group)
>      if (g_str_equal(group, "object") ||
>          g_str_equal(group, "machine") ||
>          g_str_equal(group, "smp-opts") ||
> -        g_str_equal(group, "boot-opts") ||
> -        g_str_equal(group, "memory")) {
> +        g_str_equal(group, "boot-opts")) {
>          return false;
>      }
>      return true;
> @@ -2078,8 +2081,6 @@ static void qemu_record_config_group(const char *group, 
> QDict *dict,
>          machine_merge_property("smp", dict, &error_fatal);
>      } else if (g_str_equal(group, "boot-opts")) {
>          machine_merge_property("boot", dict, &error_fatal);
> -    } else if (g_str_equal(group, "memory")) {
> -        machine_merge_property("memory", dict, &error_fatal);
>      } else {
>          abort();
>      }
> @@ -2882,7 +2883,10 @@ void qemu_init(int argc, char **argv, char **envp)
>                  exit(0);
>                  break;
>              case QEMU_OPTION_m:
> -                parse_memory_options(optarg);
> +                opts = qemu_opts_parse_noisily(qemu_find_opts("memory"), 
> optarg, true);
> +                if (opts == NULL) {
> +                    exit(1);
> +                }
>                  break;
>  #ifdef CONFIG_TPM
>              case QEMU_OPTION_tpmdev:

The previous three hunks revert commit ce9d03fb3f's switch from QemuOpts
to qemu_record_config_group().  Makes sense.

> @@ -3515,6 +3519,9 @@ void qemu_init(int argc, char **argv, char **envp)
>  
>      configure_rtc(qemu_find_opts_singleton("rtc"));
>  
> +    /* Transfer QemuOpts options into machine options */
> +    parse_memory_options();
> +
>      qemu_create_machine(machine_opts_dict);
>  
>      suspend_mux_open();

We used to call set_memory_options() early in qemu_create_machine().
Calling it here now should work, too.  Pointing out to make sure it's
not an accident.