[PATCH 2/2] accel/tcg: interrupt/exception handling uses bql_interrupt flag

[Robert Foley]

This change removes the implied BQL from the cpu_handle_interrupt,
and cpu_handle_exception paths. We can now select per-arch if
the BQL is needed or not by using the bql_interrupt flag.
By default, the core code holds the BQL.
One benefit of this change is that it leaves it up to the arch
to make the change to remove BQL when it makes sense.

Signed-off-by: Robert Foley <robert.foley@linaro.org>
---
 accel/tcg/cpu-exec.c | 34 ++++++++++++++++++++++++++--------
 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
index 80d0e649b2..cde27ee0bf 100644
--- a/accel/tcg/cpu-exec.c
+++ b/accel/tcg/cpu-exec.c
@@ -517,9 +517,13 @@ static inline bool cpu_handle_exception(CPUState *cpu, int 
*ret)
 #else
         if (replay_exception()) {
             CPUClass *cc = CPU_GET_CLASS(cpu);
-            qemu_mutex_lock_iothread();
+            if (cc->bql_interrupt) {
+                qemu_mutex_lock_iothread();
+            }
             cc->do_interrupt(cpu);
-            qemu_mutex_unlock_iothread();
+            if (cc->bql_interrupt) {
+                qemu_mutex_unlock_iothread();
+            }
             cpu->exception_index = -1;
 
             if (unlikely(cpu->singlestep_enabled)) {
@@ -558,7 +562,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
     if (unlikely(cpu_interrupt_request(cpu))) {
         int interrupt_request;
 
-        qemu_mutex_lock_iothread();
+        cpu_mutex_lock(cpu);
         interrupt_request = cpu_interrupt_request(cpu);
         if (unlikely(cpu->singlestep_enabled & SSTEP_NOIRQ)) {
             /* Mask out external interrupts for this step. */
@@ -567,7 +571,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
         if (interrupt_request & CPU_INTERRUPT_DEBUG) {
             cpu_reset_interrupt(cpu, CPU_INTERRUPT_DEBUG);
             cpu->exception_index = EXCP_DEBUG;
-            qemu_mutex_unlock_iothread();
+            cpu_mutex_unlock(cpu);
             return true;
         }
         if (replay_mode == REPLAY_MODE_PLAY && !replay_has_interrupt()) {
@@ -577,13 +581,15 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
             cpu_reset_interrupt(cpu, CPU_INTERRUPT_HALT);
             cpu_halted_set(cpu, 1);
             cpu->exception_index = EXCP_HLT;
-            qemu_mutex_unlock_iothread();
+            cpu_mutex_unlock(cpu);
             return true;
         }
 #if defined(TARGET_I386)
         else if (interrupt_request & CPU_INTERRUPT_INIT) {
             X86CPU *x86_cpu = X86_CPU(cpu);
             CPUArchState *env = &x86_cpu->env;
+            cpu_mutex_unlock(cpu);
+            qemu_mutex_lock_iothread();
             replay_interrupt();
             cpu_svm_check_intercept_param(env, SVM_EXIT_INIT, 0, 0);
             do_cpu_init(x86_cpu);
@@ -595,7 +601,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
         else if (interrupt_request & CPU_INTERRUPT_RESET) {
             replay_interrupt();
             cpu_reset(cpu);
-            qemu_mutex_unlock_iothread();
+            cpu_mutex_unlock(cpu);
             return true;
         }
 #endif
@@ -604,7 +610,15 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
            True when it is, and we should restart on a new TB,
            and via longjmp via cpu_loop_exit.  */
         else {
+            cpu_mutex_unlock(cpu);
+            if (cc->bql_interrupt) {
+                qemu_mutex_lock_iothread();
+            }
             if (cc->cpu_exec_interrupt(cpu, interrupt_request)) {
+                if (cc->bql_interrupt) {
+                    qemu_mutex_unlock_iothread();
+                }
+                cpu_mutex_lock(cpu);
                 replay_interrupt();
                 /*
                  * After processing the interrupt, ensure an EXCP_DEBUG is
@@ -614,6 +628,11 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
                 cpu->exception_index =
                     (cpu->singlestep_enabled ? EXCP_DEBUG : -1);
                 *last_tb = NULL;
+            } else {
+                if (cc->bql_interrupt) {
+                    qemu_mutex_unlock_iothread();
+                }
+                cpu_mutex_lock(cpu);
             }
             /* The target hook may have updated the 'cpu->interrupt_request';
              * reload the 'interrupt_request' value */
@@ -627,7 +646,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
         }
 
         /* If we exit via cpu_loop_exit/longjmp it is reset in cpu_exec */
-        qemu_mutex_unlock_iothread();
+        cpu_mutex_unlock(cpu);
     }
 
     /* Finally, check if we need to exit to the main loop.  */
@@ -691,7 +710,6 @@ static inline void cpu_loop_exec_tb(CPUState *cpu, 
TranslationBlock *tb,
     }
 #endif
 }
-
 /* main execution loop */
 
 int cpu_exec(CPUState *cpu)
-- 
2.17.1