[Qemu-devel] [PATCH v2] target/xtensa: fix access to the INTERRUPT SR

[Max Filippov]

INTERRUPT special register may be changed both by the core (by writing
to INTSET and INTCLEAR registers) and by external events (by triggering
and clearing HW IRQs). In MTTCG this state must be protected from
concurrent access, otherwise interrupts may be lost or spurious
interrupts may be detected.

Use atomic operations to change INTSET SR.
Fix wsr.intset so that it soesn't clear any bits.
Fix wsr.intclear so that it doesn't clear bit that corresponds to NMI.

Signed-off-by: Max Filippov <address@hidden>
---
Changes v1->v2:
- use atomic operations to change INTSET SR. Don't use BQL in the
  CPU-side helpers as there's nothing else to synchronize..

 hw/xtensa/pic_cpu.c        |  4 ++--
 target/xtensa/exc_helper.c | 13 +++++++++++++
 target/xtensa/helper.h     |  2 ++
 target/xtensa/op_helper.c  |  2 ++
 target/xtensa/translate.c  | 14 ++------------
 5 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/hw/xtensa/pic_cpu.c b/hw/xtensa/pic_cpu.c
index 0e812d7f061c..7e4c65e5ec30 100644
--- a/hw/xtensa/pic_cpu.c
+++ b/hw/xtensa/pic_cpu.c
@@ -68,9 +68,9 @@ static void xtensa_set_irq(void *opaque, int irq, int active)
         uint32_t irq_bit = 1 << irq;
 
         if (active) {
-            env->sregs[INTSET] |= irq_bit;
+            atomic_or(&env->sregs[INTSET], irq_bit);
         } else if (env->config->interrupt[irq].inttype == INTTYPE_LEVEL) {
-            env->sregs[INTSET] &= ~irq_bit;
+            atomic_and(&env->sregs[INTSET], ~irq_bit);
         }
 
         check_interrupts(env);
diff --git a/target/xtensa/exc_helper.c b/target/xtensa/exc_helper.c
index 371a32ba5ad9..4a1f7aef5dcf 100644
--- a/target/xtensa/exc_helper.c
+++ b/target/xtensa/exc_helper.c
@@ -127,6 +127,19 @@ void HELPER(check_interrupts)(CPUXtensaState *env)
     qemu_mutex_unlock_iothread();
 }
 
+void HELPER(intset)(CPUXtensaState *env, uint32_t v)
+{
+    atomic_or(&env->sregs[INTSET],
+              v & env->config->inttype_mask[INTTYPE_SOFTWARE]);
+}
+
+void HELPER(intclear)(CPUXtensaState *env, uint32_t v)
+{
+    atomic_and(&env->sregs[INTSET],
+               ~(v & (env->config->inttype_mask[INTTYPE_SOFTWARE] |
+                      env->config->inttype_mask[INTTYPE_EDGE])));
+}
+
 static uint32_t relocated_vector(CPUXtensaState *env, uint32_t vector)
 {
     if (xtensa_option_enabled(env->config,
diff --git a/target/xtensa/helper.h b/target/xtensa/helper.h
index 89eb97e26514..2a7db35874fe 100644
--- a/target/xtensa/helper.h
+++ b/target/xtensa/helper.h
@@ -22,6 +22,8 @@ DEF_HELPER_1(update_ccount, void, env)
 DEF_HELPER_2(wsr_ccount, void, env, i32)
 DEF_HELPER_2(update_ccompare, void, env, i32)
 DEF_HELPER_1(check_interrupts, void, env)
+DEF_HELPER_2(intset, void, env, i32)
+DEF_HELPER_2(intclear, void, env, i32)
 DEF_HELPER_3(check_atomctl, void, env, i32, i32)
 DEF_HELPER_2(wsr_memctl, void, env, i32)
 
diff --git a/target/xtensa/op_helper.c b/target/xtensa/op_helper.c
index 1865f46c4b5f..04971b044fac 100644
--- a/target/xtensa/op_helper.c
+++ b/target/xtensa/op_helper.c
@@ -62,6 +62,8 @@ void HELPER(update_ccompare)(CPUXtensaState *env, uint32_t i)
 {
     uint64_t dcc;
 
+    atomic_and(&env->sregs[INTSET],
+               ~(1u << env->config->timerint[i]));
     HELPER(update_ccount)(env);
     dcc = (uint64_t)(env->sregs[CCOMPARE + i] - env->sregs[CCOUNT] - 1) + 1;
     timer_mod(env->ccompare[i].timer,
diff --git a/target/xtensa/translate.c b/target/xtensa/translate.c
index a435d9c36cf1..d1e9f59b31bd 100644
--- a/target/xtensa/translate.c
+++ b/target/xtensa/translate.c
@@ -646,20 +646,12 @@ static void gen_check_interrupts(DisasContext *dc)
 
 static void gen_wsr_intset(DisasContext *dc, uint32_t sr, TCGv_i32 v)
 {
-    tcg_gen_andi_i32(cpu_SR[sr], v,
-            dc->config->inttype_mask[INTTYPE_SOFTWARE]);
+    gen_helper_intset(cpu_env, v);
 }
 
 static void gen_wsr_intclear(DisasContext *dc, uint32_t sr, TCGv_i32 v)
 {
-    TCGv_i32 tmp = tcg_temp_new_i32();
-
-    tcg_gen_andi_i32(tmp, v,
-            dc->config->inttype_mask[INTTYPE_EDGE] |
-            dc->config->inttype_mask[INTTYPE_NMI] |
-            dc->config->inttype_mask[INTTYPE_SOFTWARE]);
-    tcg_gen_andc_i32(cpu_SR[INTSET], cpu_SR[INTSET], tmp);
-    tcg_temp_free(tmp);
+    gen_helper_intclear(cpu_env, v);
 }
 
 static void gen_wsr_intenable(DisasContext *dc, uint32_t sr, TCGv_i32 v)
@@ -706,12 +698,10 @@ static void gen_wsr_icountlevel(DisasContext *dc, 
uint32_t sr, TCGv_i32 v)
 static void gen_wsr_ccompare(DisasContext *dc, uint32_t sr, TCGv_i32 v)
 {
     uint32_t id = sr - CCOMPARE;
-    uint32_t int_bit = 1 << dc->config->timerint[id];
     TCGv_i32 tmp = tcg_const_i32(id);
 
     assert(id < dc->config->nccompare);
     tcg_gen_mov_i32(cpu_SR[sr], v);
-    tcg_gen_andi_i32(cpu_SR[INTSET], cpu_SR[INTSET], ~int_bit);
     if (tb_cflags(dc->base.tb) & CF_USE_ICOUNT) {
         gen_io_start();
     }
-- 
2.11.0