Re: [PATCH v2 02/14] plugins: scoreboard API

[Pierrick Bouvier]

On 1/26/24 19:14, Alex Bennée wrote:
> > +        need_realloc = TRUE;
> > +    }
> > +    plugin.scoreboard_size = cpu->cpu_index + 1;
> > +    g_assert(plugin.scoreboard_size <= plugin.scoreboard_alloc_size);
> > +
> > +    if (g_hash_table_size(plugin.scoreboards) == 0) {
> > +        /* nothing to do, we just updated sizes for future scoreboards */
> > +        return;
> > +    }
> > +
> > +    if (need_realloc) {
> > +#ifdef CONFIG_USER_ONLY
> > +        /**
> > +         * cpus must be stopped, as some tb might still use an existing
> > +         * scoreboard.
> > +         */
> > +        start_exclusive();
> > +#endif
>
> Hmm this seems wrong to be USER_ONLY. While we don't expect to resize in
> system mode if we did we certainly want to do it during exclusive
> periods.

After investigation, current_cpu TLS var is not set in cpus-common.c at 
this point.

Indeed we are not on any cpu_exec path, but in the cpu_realize_fn when 
calling this (through qemu_plugin_vcpu_init_hook).

One obvious fix is to check if it's NULL or not, like:
--- a/cpu-common.c
+++ b/cpu-common.c
@@ -193,7 +193,7 @@ void start_exclusive(void)
     CPUState *other_cpu;
     int running_cpus;

-    if (current_cpu->exclusive_context_count) {
+    if (current_cpu && current_cpu->exclusive_context_count) {
         current_cpu->exclusive_context_count++;
         return;
     }

Does anyone suggest another possible fix? (like define current_cpu 
somewhere, or moving qemu_plugin_vcpu_init_hook call).