Re: [PATCH] accel: Do not set CPUState::can_do_io in non-TCG accels

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

Hi Claudio,

On 30/11/23 13:48, Claudio Fontana wrote:
> Hi Philippe,
> 
> took a quick look with
> 
> grep -R can_do_io
> 
> and this seems to be in include/hw/core/cpu.h as well as cpu-common.c,
> 
> maybe there is more meat to address to fully solve this?
> 
> Before we had stuff for reset in cpu-common.c under a
> if (tcg_enabled()) {
> }
> 
> but now we have cpu_exec_reset_hold(),
> should the implementation for tcg of cpu_exec_reset_hold() do that (and potentially other tcg-specific non-arch-specific cpu variables we might need)?

Later we eventually get there:

diff --git a/accel/tcg/tcg-accel-ops.c b/accel/tcg/tcg-accel-ops.c
index 9b038b1af5..e2c5cf97dc 100644
--- a/accel/tcg/tcg-accel-ops.c
+++ b/accel/tcg/tcg-accel-ops.c
@@ -89,6 +89,9 @@ static void tcg_cpu_reset_hold(CPUState *cpu)

      cpu->accel->icount_extra = 0;
      cpu->accel->mem_io_pc = 0;
+
+    qatomic_set(&cpu->neg.icount_decr.u32, 0);
+    cpu->neg.can_do_io = true;
  }

My branch is huge, I'm trying to split it, maybe I shouldn't have
sent this single non-TCG patch out of it. I'll Cc you.

> If can_do_io is TCG-specific, maybe the whole field existence / visibility can be conditioned on TCG actually being at least compiled-in?
> This might help find problems of the field being used in the wrong context, by virtue of getting an error when compiling with --disable-tcg for example.
> 
> Ciao,
> 
> Claudio