> I have been testing TCG plugin patch on latest Qemu build but noticed that it
> fails with assert on some of the applications.
>
> ERROR:../accel/tcg/cpu-exec.c:983:cpu_exec_loop:
> assertion failed: (cpu->plugin_mem_cbs == ((void *)0))
>
It seems that the problem is around tcg_ctx->plugin_tb->mem_helper flag. It is
set to true
by inject_mem_enable_helper() if plugin requests memory callbacks injection and
checked
by inject_mem_disable_helper() to insert appropriate cleanup code at the end.
It works if
translation block has single exit point. However if translation block has
branches or exits,
inject_mem_disable_helper() is called during code generation prepending all tb
exits.
Unfortunately it happens before inject_mem_enable_helper() initializes
mem_helper flag for
that block.
I’ve tried quick fix by commenting out this check in
inject_mem_disable_helper() so that clean
up code is inserted unconditionally on every exit. The assert is gone.
What would be a better way to fix it?
diff --git a/accel/tcg/plugin-gen.c b/accel/tcg/plugin-gen.c
index 17a686bd9e..6651874c0f 100644
--- a/accel/tcg/plugin-gen.c
+++ b/accel/tcg/plugin-gen.c
@@ -637,9 +637,9 @@ void plugin_gen_disable_mem_helpers(void)
* Note: we do not reset plugin_tb->mem_helper here; a TB might have
several
* exit points, and we want to emit the clearing from all of them.
*/
- if (!tcg_ctx->plugin_tb->mem_helper) {
- return;
- }
+ // if (!tcg_ctx->plugin_tb->mem_helper) {
+ // return;
+ // }
ptr = tcg_const_ptr(NULL);
tcg_gen_st_ptr(ptr, cpu_env, offsetof(CPUState, plugin_mem_cbs) -
offsetof(ArchCPU, env));
