hw/mips_int: hold BQL for all interrupt requests

Make sure BQL is held for all interrupt requests.

For MTTCG-enabled configurations, handling soft and hard interrupts
between vCPUs must be properly locked. By acquiring BQL, make sure
all paths triggering an IRQ are synchronized.

Signed-off-by: Miodrag Dinic <miodrag.dinic@imgtec.com>
Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Acked-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

hw/mips/mips_int.c

@@ -21,6 +21,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/main-loop.h"
 #include "hw/hw.h"
 #include "hw/mips/cpudevs.h"
 #include "cpu.h"
@@ -32,10 +33,17 @@ static void cpu_mips_irq_request(void *opaque, int irq, int level)
     MIPSCPU *cpu = opaque;
     CPUMIPSState *env = &cpu->env;
     CPUState *cs = CPU(cpu);
+    bool locked = false;
 
     if (irq < 0 || irq > 7)
         return;
 
+    /* Make sure locking works even if BQL is already held by the caller */
+    if (!qemu_mutex_iothread_locked()) {
+        locked = true;
+        qemu_mutex_lock_iothread();
+    }
+
     if (level) {
         env->CP0_Cause |= 1 << (irq + CP0Ca_IP);
 
@@ -56,6 +64,10 @@ static void cpu_mips_irq_request(void *opaque, int irq, int level)
     } else {
         cpu_reset_interrupt(cs, CPU_INTERRUPT_HARD);
     }
+
+    if (locked) {
+        qemu_mutex_unlock_iothread();
+    }
 }
 
 void cpu_mips_irq_init_cpu(MIPSCPU *cpu)

target/mips/op_helper.c

@@ -17,7 +17,6 @@
  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  */
 #include "qemu/osdep.h"
-#include "qemu/main-loop.h"
 #include "cpu.h"
 #include "internal.h"
 #include "qemu/host-utils.h"
@@ -905,11 +904,7 @@ target_ulong helper_mftc0_tcschefback(CPUMIPSState *env)
 
 target_ulong helper_mfc0_count(CPUMIPSState *env)
 {
-    int32_t count;
+    return (int32_t)cpu_mips_get_count(env);
-    qemu_mutex_lock_iothread();
-    count = (int32_t) cpu_mips_get_count(env);
-    qemu_mutex_unlock_iothread();
-    return count;
 }
 
 target_ulong helper_mfc0_saar(CPUMIPSState *env)
@@ -1594,9 +1589,7 @@ void helper_mtc0_hwrena(CPUMIPSState *env, target_ulong arg1)
 
 void helper_mtc0_count(CPUMIPSState *env, target_ulong arg1)
 {
-    qemu_mutex_lock_iothread();
     cpu_mips_store_count(env, arg1);
-    qemu_mutex_unlock_iothread();
 }
 
 void helper_mtc0_saari(CPUMIPSState *env, target_ulong arg1)
@@ -1685,9 +1678,7 @@ void helper_mttc0_entryhi(CPUMIPSState *env, target_ulong arg1)
 
 void helper_mtc0_compare(CPUMIPSState *env, target_ulong arg1)
 {
-    qemu_mutex_lock_iothread();
     cpu_mips_store_compare(env, arg1);
-    qemu_mutex_unlock_iothread();
 }
 
 void helper_mtc0_status(CPUMIPSState *env, target_ulong arg1)
@@ -1741,9 +1732,7 @@ void helper_mtc0_srsctl(CPUMIPSState *env, target_ulong arg1)
 
 void helper_mtc0_cause(CPUMIPSState *env, target_ulong arg1)
 {
-    qemu_mutex_lock_iothread();
     cpu_mips_store_cause(env, arg1);
-    qemu_mutex_unlock_iothread();
 }
 
 void helper_mttc0_cause(CPUMIPSState *env, target_ulong arg1)
@@ -2587,16 +2576,12 @@ target_ulong helper_rdhwr_synci_step(CPUMIPSState *env)
 
 target_ulong helper_rdhwr_cc(CPUMIPSState *env)
 {
-    int32_t count;
     check_hwrena(env, 2, GETPC());
 #ifdef CONFIG_USER_ONLY
-    count = env->CP0_Count;
+    return env->CP0_Count;
 #else
-    qemu_mutex_lock_iothread();
+    return (int32_t)cpu_mips_get_count(env);
-    count = (int32_t)cpu_mips_get_count(env);
-    qemu_mutex_unlock_iothread();
 #endif
-    return count;
 }
 
 target_ulong helper_rdhwr_ccres(CPUMIPSState *env)