[Qemu-devel] [PATCH 2/5] s390x/kvm: run guest triggered resets on the target vcpu thread

[Jens Freimann <jfrei@linux.vnet.ibm.com>]

From: David Hildenbrand <dahi@linux.vnet.ibm.com>

Currently, load_normal_reset() and modified_clear_reset() as triggered
by a guest vcpu will initiate cpu resets on the current vcpu thread for
all cpus. The reset should happen on the individual vcpu thread
instead, so let's use run_on_cpu() for this.

This avoids calls to synchronize_rcu() in the kernel.

Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
---
 target-s390x/cpu.h         | 15 +++++++++++++++
 target-s390x/misc_helper.c | 30 ++++++++----------------------
 2 files changed, 23 insertions(+), 22 deletions(-)

diff --git a/target-s390x/cpu.h b/target-s390x/cpu.h
index b13761d..17a3df4 100644
--- a/target-s390x/cpu.h
+++ b/target-s390x/cpu.h
@@ -353,6 +353,21 @@ static inline hwaddr decode_basedisp_s(CPUS390XState *env, uint32_t ipb)
 /* Base/displacement are at the same locations. */
 #define decode_basedisp_rs decode_basedisp_s
 
+/* helper functions for run_on_cpu() */
+static inline void s390_do_cpu_reset(void *arg)
+{
+    CPUState *cs = arg;
+    S390CPUClass *scc = S390_CPU_GET_CLASS(cs);
+
+    scc->cpu_reset(cs);
+}
+static inline void s390_do_cpu_full_reset(void *arg)
+{
+    CPUState *cs = arg;
+
+    cpu_reset(cs);
+}
+
 void s390x_tod_timer(void *opaque);
 void s390x_cpu_timer(void *opaque);
 
diff --git a/target-s390x/misc_helper.c b/target-s390x/misc_helper.c
index 0b62582..ef9758a 100644
--- a/target-s390x/misc_helper.c
+++ b/target-s390x/misc_helper.c
@@ -114,33 +114,16 @@ uint32_t HELPER(servc)(CPUS390XState *env, uint64_t r1, uint64_t r2)
 }
 
 #ifndef CONFIG_USER_ONLY
-static void cpu_reset_all(void)
-{
-    CPUState *cs;
-    S390CPUClass *scc;
-
-    CPU_FOREACH(cs) {
-        scc = S390_CPU_GET_CLASS(cs);
-        scc->cpu_reset(cs);
-    }
-}
-
-static void cpu_full_reset_all(void)
-{
-    CPUState *cpu;
-
-    CPU_FOREACH(cpu) {
-        cpu_reset(cpu);
-    }
-}
-
 static int modified_clear_reset(S390CPU *cpu)
 {
     S390CPUClass *scc = S390_CPU_GET_CLASS(cpu);
+    CPUState *t;
 
     pause_all_vcpus();
     cpu_synchronize_all_states();
-    cpu_full_reset_all();
+    CPU_FOREACH(t) {
+        run_on_cpu(t, s390_do_cpu_full_reset, t);
+    }
     cmma_reset(cpu);
     io_subsystem_reset();
     scc->load_normal(CPU(cpu));
@@ -152,10 +135,13 @@ static int modified_clear_reset(S390CPU *cpu)
 static int load_normal_reset(S390CPU *cpu)
 {
     S390CPUClass *scc = S390_CPU_GET_CLASS(cpu);
+    CPUState *t;
 
     pause_all_vcpus();
     cpu_synchronize_all_states();
-    cpu_reset_all();
+    CPU_FOREACH(t) {
+        run_on_cpu(t, s390_do_cpu_reset, t);
+    }
     cmma_reset(cpu);
     io_subsystem_reset();
     scc->initial_cpu_reset(CPU(cpu));
-- 
1.9.3