Re: [PATCH 3/3] target/nios2: Use gen_io_start around wrctl instruction

[Max Filippov]

On Sun, Jul 5, 2020 at 10:09 AM Peter Maydell <peter.maydell@linaro.org> wrote:
> On Thu, 2 Jul 2020 at 19:53, Richard Henderson
> <richard.henderson@linaro.org> wrote:
> > This isn't right.  Not so much the gen_io_start portion, but the entire
> > existence of helper_check_interrupt.
>
> I agree that it looks bogus (xtensa has a similar helper as well, 
> incidentally),

I think there was a reason for it. According to Richard

> The correct way to acknowledge interrupts after changing an interrupt mask bit
> is to exit the TB back to the cpu main loop.

But if I do this change for Xtensa I get a bunch of test_interrupt failures
that indicate that the interrupt that should have been taken wasn't taken.
FTR here's the change that I tested, did I miss something?

diff --git a/target/xtensa/translate.c b/target/xtensa/translate.c
index fdf47642e6f1..85e8d65f169d 100644
--- a/target/xtensa/translate.c
+++ b/target/xtensa/translate.c
@@ -631,18 +631,10 @@ static int gen_postprocess(DisasContext *dc, int slot)
 {
     uint32_t op_flags = dc->op_flags;

-#ifndef CONFIG_USER_ONLY
-    if (op_flags & XTENSA_OP_CHECK_INTERRUPTS) {
-        if (tb_cflags(dc->base.tb) & CF_USE_ICOUNT) {
-            gen_io_start();
-        }
-        gen_helper_check_interrupts(cpu_env);
-    }
-#endif
     if (op_flags & XTENSA_OP_SYNC_REGISTER_WINDOW) {
         gen_helper_sync_windowbase(cpu_env);
     }
-    if (op_flags & XTENSA_OP_EXIT_TB_M1) {
+    if (op_flags & (XTENSA_OP_EXIT_TB_M1 | XTENSA_OP_CHECK_INTERRUPTS)) {
         slot = -1;
     }
     return slot;
@@ -1175,7 +1167,7 @@ static void disas_xtensa_insn(CPUXtensaState
*env, DisasContext *dc)
     if (dc->base.is_jmp == DISAS_NEXT) {
         gen_postprocess(dc, 0);
         dc->op_flags = 0;
-        if (op_flags & XTENSA_OP_EXIT_TB_M1) {
+        if (op_flags & (XTENSA_OP_EXIT_TB_M1 | XTENSA_OP_CHECK_INTERRUPTS)) {
             /* Change in mmu index, memory mapping or tb->flags; exit tb */
             gen_jumpi_check_loop_end(dc, -1);
         } else if (op_flags & XTENSA_OP_EXIT_TB_0) {


-- 
Thanks.
-- Max