[Qemu-devel] [RFC PATCH] target-arm: protect cpu_exclusive_*.

[fred.konrad@greensocs.com]

From: KONRAD Frederic <fred.konrad@greensocs.com>

This adds a lock to avoid multiple exclusive access at the same time in case of
TCG multithread.

Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com>
---
 target-arm/cpu.c       | 15 +++++++++++++++
 target-arm/cpu.h       |  3 +++
 target-arm/helper.h    |  3 +++
 target-arm/op_helper.c | 10 ++++++++++
 target-arm/translate.c |  6 ++++++
 5 files changed, 37 insertions(+)

diff --git a/target-arm/cpu.c b/target-arm/cpu.c
index 5ce7350..a55017d 100644
--- a/target-arm/cpu.c
+++ b/target-arm/cpu.c
@@ -31,6 +31,19 @@
 #include "sysemu/kvm.h"
 #include "kvm_arm.h"
 
+/* Protect cpu_exclusive_* variable .*/
+QemuMutex cpu_exclusive_lock;
+
+inline void arm_exclusive_lock(void)
+{
+    qemu_mutex_lock(&cpu_exclusive_lock);
+}
+
+inline void arm_exclusive_unlock(void)
+{
+    qemu_mutex_unlock(&cpu_exclusive_lock);
+}
+
 static void arm_cpu_set_pc(CPUState *cs, vaddr value)
 {
     ARMCPU *cpu = ARM_CPU(cs);
@@ -365,6 +378,7 @@ static void arm_cpu_initfn(Object *obj)
         cpu->psci_version = 2; /* TCG implements PSCI 0.2 */
         if (!inited) {
             inited = true;
+            qemu_mutex_init(&cpu_exclusive_lock);
             arm_translate_init();
         }
     }
@@ -404,6 +418,7 @@ static void arm_cpu_finalizefn(Object *obj)
 {
     ARMCPU *cpu = ARM_CPU(obj);
     g_hash_table_destroy(cpu->cp_regs);
+    qemu_mutex_destroy(&cpu_exclusive_lock);
 }
 
 static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
diff --git a/target-arm/cpu.h b/target-arm/cpu.h
index 7f80090..f01c9ef 100644
--- a/target-arm/cpu.h
+++ b/target-arm/cpu.h
@@ -1539,4 +1539,7 @@ enum {
     QEMU_PSCI_CONDUIT_HVC = 2,
 };
 
+void arm_exclusive_lock(void);
+void arm_exclusive_unlock(void);
+
 #endif
diff --git a/target-arm/helper.h b/target-arm/helper.h
index dec3728..ce07711 100644
--- a/target-arm/helper.h
+++ b/target-arm/helper.h
@@ -529,6 +529,9 @@ DEF_HELPER_2(dc_zva, void, env, i64)
 DEF_HELPER_FLAGS_2(neon_pmull_64_lo, TCG_CALL_NO_RWG_SE, i64, i64, i64)
 DEF_HELPER_FLAGS_2(neon_pmull_64_hi, TCG_CALL_NO_RWG_SE, i64, i64, i64)
 
+DEF_HELPER_0(exclusive_lock, void)
+DEF_HELPER_0(exclusive_unlock, void)
+
 #ifdef TARGET_AARCH64
 #include "helper-a64.h"
 #endif
diff --git a/target-arm/op_helper.c b/target-arm/op_helper.c
index 62012c3..916772f 100644
--- a/target-arm/op_helper.c
+++ b/target-arm/op_helper.c
@@ -33,6 +33,16 @@ static void raise_exception(CPUARMState *env, int tt)
     cpu_loop_exit(cs);
 }
 
+void HELPER(exclusive_lock)(void)
+{
+    arm_exclusive_lock();
+}
+
+void HELPER(exclusive_unlock)(void)
+{
+    arm_exclusive_unlock();
+}
+
 uint32_t HELPER(neon_tbl)(CPUARMState *env, uint32_t ireg, uint32_t def,
                           uint32_t rn, uint32_t maxindex)
 {
diff --git a/target-arm/translate.c b/target-arm/translate.c
index af51568..4a82ad5 100644
--- a/target-arm/translate.c
+++ b/target-arm/translate.c
@@ -7377,6 +7377,7 @@ static void gen_load_exclusive(DisasContext *s, int rt, int rt2,
         abort();
     }
 
+    gen_helper_exclusive_lock();
     if (size == 3) {
         TCGv_i32 tmp2 = tcg_temp_new_i32();
         TCGv_i32 tmp3 = tcg_temp_new_i32();
@@ -7392,11 +7393,14 @@ static void gen_load_exclusive(DisasContext *s, int rt, int rt2,
 
     store_reg(s, rt, tmp);
     tcg_gen_extu_i32_i64(cpu_exclusive_addr, addr);
+    gen_helper_exclusive_unlock();
 }
 
 static void gen_clrex(DisasContext *s)
 {
+    gen_helper_exclusive_lock();
     tcg_gen_movi_i64(cpu_exclusive_addr, -1);
+    gen_helper_exclusive_unlock();
 }
 
 #ifdef CONFIG_USER_ONLY
@@ -7427,6 +7431,7 @@ static void gen_store_exclusive(DisasContext *s, int rd, int rt, int rt2,
     done_label = gen_new_label();
     extaddr = tcg_temp_new_i64();
     tcg_gen_extu_i32_i64(extaddr, addr);
+    gen_helper_exclusive_lock();
     tcg_gen_brcond_i64(TCG_COND_NE, extaddr, cpu_exclusive_addr, fail_label);
     tcg_temp_free_i64(extaddr);
 
@@ -7491,6 +7496,7 @@ static void gen_store_exclusive(DisasContext *s, int rd, int rt, int rt2,
     tcg_gen_movi_i32(cpu_R[rd], 1);
     gen_set_label(done_label);
     tcg_gen_movi_i64(cpu_exclusive_addr, -1);
+    gen_helper_exclusive_unlock();
 }
 #endif
 
-- 
1.9.0