[PATCH 3/8] accel: use atomic accesses for exit_request

[Paolo Bonzini <pbonzini@redhat.com>]

CPU threads write exit_request as a "note to self" that they need to
go out to a slow path.  This write happens out of the BQL and can be
a data race with another threads' cpu_exit(); use atomic accesses
consistently.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 accel/tcg/tcg-accel-ops-mttcg.c   | 2 +-
 accel/tcg/tcg-accel-ops-rr.c      | 4 ++--
 hw/ppc/spapr_hcall.c              | 6 +++---
 target/i386/kvm/kvm.c             | 2 +-
 target/i386/nvmm/nvmm-accel-ops.c | 2 +-
 target/i386/nvmm/nvmm-all.c       | 2 +-
 target/i386/whpx/whpx-all.c       | 6 +++---
 7 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/accel/tcg/tcg-accel-ops-mttcg.c b/accel/tcg/tcg-accel-ops-mttcg.c
index 337b993d3da..39237421757 100644
--- a/accel/tcg/tcg-accel-ops-mttcg.c
+++ b/accel/tcg/tcg-accel-ops-mttcg.c
@@ -85,7 +85,7 @@ static void *mttcg_cpu_thread_fn(void *arg)
     qemu_guest_random_seed_thread_part2(cpu->random_seed);
 
     /* process any pending work */
-    cpu->exit_request = 1;
+    qatomic_set(&cpu->exit_request, 1);
 
     do {
         if (cpu_can_run(cpu)) {
diff --git a/accel/tcg/tcg-accel-ops-rr.c b/accel/tcg/tcg-accel-ops-rr.c
index 1e551e92d6d..c06f3beef2e 100644
--- a/accel/tcg/tcg-accel-ops-rr.c
+++ b/accel/tcg/tcg-accel-ops-rr.c
@@ -212,7 +212,7 @@ static void *rr_cpu_thread_fn(void *arg)
     cpu = first_cpu;
 
     /* process any pending work */
-    cpu->exit_request = 1;
+    qatomic_set(&cpu->exit_request, 1);
 
     while (1) {
         /* Only used for icount_enabled() */
@@ -286,7 +286,7 @@ static void *rr_cpu_thread_fn(void *arg)
         /* Does not need a memory barrier because a spurious wakeup is okay.  */
         qatomic_set(&rr_current_cpu, NULL);
 
-        if (cpu && cpu->exit_request) {
+        if (cpu && qatomic_read(&cpu->exit_request)) {
             qatomic_set_mb(&cpu->exit_request, 0);
         }
 
diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
index 1e936f35e44..03a62b047b3 100644
--- a/hw/ppc/spapr_hcall.c
+++ b/hw/ppc/spapr_hcall.c
@@ -509,7 +509,7 @@ static target_ulong h_cede(PowerPCCPU *cpu, SpaprMachineState *spapr,
     if (!cpu_has_work(cs)) {
         cs->halted = 1;
         cs->exception_index = EXCP_HLT;
-        cs->exit_request = 1;
+        qatomic_set(&cs->exit_request, 1);
         ppc_maybe_interrupt(env);
     }
 
@@ -531,7 +531,7 @@ static target_ulong h_confer_self(PowerPCCPU *cpu)
     }
     cs->halted = 1;
     cs->exception_index = EXCP_HALTED;
-    cs->exit_request = 1;
+    qatomic_set(&cs->exit_request, 1);
     ppc_maybe_interrupt(&cpu->env);
 
     return H_SUCCESS;
@@ -624,7 +624,7 @@ static target_ulong h_confer(PowerPCCPU *cpu, SpaprMachineState *spapr,
     }
 
     cs->exception_index = EXCP_YIELD;
-    cs->exit_request = 1;
+    qatomic_set(&cs->exit_request, 1);
     cpu_loop_exit(cs);
 
     return H_SUCCESS;
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 306430a0521..867eabc6969 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -5604,7 +5604,7 @@ int kvm_arch_process_async_events(CPUState *cs)
         if (env->exception_nr == EXCP08_DBLE) {
             /* this means triple fault */
             qemu_system_reset_request(SHUTDOWN_CAUSE_GUEST_RESET);
-            cs->exit_request = 1;
+            qatomic_set(&cs->exit_request, 1);
             return 0;
         }
         kvm_queue_exception(env, EXCP12_MCHK, 0, 0);
diff --git a/target/i386/nvmm/nvmm-accel-ops.c b/target/i386/nvmm/nvmm-accel-ops.c
index 3799260bbde..3658a583bc8 100644
--- a/target/i386/nvmm/nvmm-accel-ops.c
+++ b/target/i386/nvmm/nvmm-accel-ops.c
@@ -77,7 +77,7 @@ static void nvmm_start_vcpu_thread(CPUState *cpu)
  */
 static void nvmm_kick_vcpu_thread(CPUState *cpu)
 {
-    cpu->exit_request = 1;
+    qatomic_set(&cpu->exit_request, 1);
     cpus_kick_thread(cpu);
 }
 
diff --git a/target/i386/nvmm/nvmm-all.c b/target/i386/nvmm/nvmm-all.c
index a5e3485c1f8..d2d90f38976 100644
--- a/target/i386/nvmm/nvmm-all.c
+++ b/target/i386/nvmm/nvmm-all.c
@@ -414,7 +414,7 @@ nvmm_vcpu_pre_run(CPUState *cpu)
      * or commit pending TPR access.
      */
     if (cpu_test_interrupt(cpu, CPU_INTERRUPT_INIT | CPU_INTERRUPT_TPR)) {
-        cpu->exit_request = 1;
+        qatomic_set(&cpu->exit_request, 1);
     }
 
     if (!has_event && cpu_test_interrupt(cpu, CPU_INTERRUPT_NMI)) {
diff --git a/target/i386/whpx/whpx-all.c b/target/i386/whpx/whpx-all.c
index 9f88e368d4d..9b07716121a 100644
--- a/target/i386/whpx/whpx-all.c
+++ b/target/i386/whpx/whpx-all.c
@@ -1489,10 +1489,10 @@ static void whpx_vcpu_pre_run(CPUState *cpu)
     if (cpu_test_interrupt(cpu, CPU_INTERRUPT_INIT | CPU_INTERRUPT_TPR)) {
         if (cpu_test_interrupt(cpu, CPU_INTERRUPT_INIT) &&
             !(env->hflags & HF_SMM_MASK)) {
-            cpu->exit_request = 1;
+            qatomic_set(&cpu->exit_request, 1);
         }
         if (cpu_test_interrupt(cpu, CPU_INTERRUPT_TPR)) {
-            cpu->exit_request = 1;
+            qatomic_set(&cpu->exit_request, 1);
         }
     }
 
@@ -1539,7 +1539,7 @@ static void whpx_vcpu_pre_run(CPUState *cpu)
     if (tpr != vcpu->tpr) {
         vcpu->tpr = tpr;
         reg_values[reg_count].Reg64 = tpr;
-        cpu->exit_request = 1;
+        qatomic_set(&cpu->exit_request, 1);
         reg_names[reg_count] = WHvX64RegisterCr8;
         reg_count += 1;
     }
-- 
2.50.1