[PATCH] qemu-kvm: fix guest resetting

Jan Kiszka
2008-05-08T08:29:32Z

Resetting guests used to be racy, deadlock-prone, or simply broken (for
SMP). This patch fixes the issues - at least for me on x86 (tested on
Intel SMP host, UP and SMP guest, in-kernel und user space irqchip,
guest- and monitor-issued resets). Note that ia64 and powerpc may need
to look into the SMP thing as well (=>kvm_arch_cpu_reset).

At this chance, the patch also cleans up some unneeded reset fragments.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
qemu/qemu-kvm-ia64.c | 4 ++++
qemu/qemu-kvm-powerpc.c | 4 ++++
qemu/qemu-kvm-x86.c | 16 ++++++++++++++++
qemu/qemu-kvm.c | 38 ++++++++++++++++++--------------------
qemu/qemu-kvm.h | 1 +
qemu/vl.c | 11 ++++++-----
6 files changed, 49 insertions(+), 25 deletions(-)

Index: b/qemu/qemu-kvm.c
===================================================================
--- a/qemu/qemu-kvm.c
+++ b/qemu/qemu-kvm.c
@@ -28,8 +28,6 @@ kvm_context_t kvm_context;

extern int smp_cpus;

-static int qemu_kvm_reset_requested;
-
pthread_mutex_t qemu_mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t qemu_aio_cond = PTHREAD_COND_INITIALIZER;
pthread_cond_t qemu_vcpu_cond = PTHREAD_COND_INITIALIZER;
@@ -56,7 +54,6 @@ struct vcpu_info {
int signalled;
int stop;
int stopped;
- int reload_regs;
int created;
} vcpu_info[256];

@@ -257,17 +254,20 @@ static int all_threads_paused(void)

static void pause_all_threads(void)
{
+ CPUState *cpu_single = cpu_single_env;
int i;

- for (i = 0; i < smp_cpus; ++i) {
- vcpu_info[i].stop = 1;
- pthread_kill(vcpu_info[i].thread, SIG_IPI);
- }
+ for (i = 0; i < smp_cpus; ++i)
+ if (!cpu_single || cpu_single->cpu_index != i) {
+ vcpu_info[i].stop = 1;
+ pthread_kill(vcpu_info[i].thread, SIG_IPI);
+ }
+
while (!all_threads_paused()) {
pthread_mutex_unlock(&qemu_mutex);
- kvm_eat_signal(&io_signal_table, NULL, 1000);
+ kvm_eat_signal(&io_signal_table, cpu_single, 1000);
pthread_mutex_lock(&qemu_mutex);
- cpu_single_env = NULL;
+ cpu_single_env = cpu_single;
}
}

@@ -317,11 +317,18 @@ void qemu_kvm_system_reset_request(void)
{
int i;

+ pause_all_threads();
+
+ qemu_system_reset();
+
+ for (i = 0; i < smp_cpus; ++i)
+ kvm_arch_cpu_reset(vcpu_info[i].env);
+
for (i = 0; i < smp_cpus; ++i) {
- vcpu_info[i].reload_regs = 1;
+ vcpu_info[i].stop = 0;
+ vcpu_info[i].stopped = 0;
pthread_kill(vcpu_info[i].thread, SIG_IPI);
}
- qemu_system_reset();
}

static int kvm_main_loop_cpu(CPUState *env)
@@ -354,11 +361,6 @@ static int kvm_main_loop_cpu(CPUState *e
kvm_cpu_exec(env);
env->interrupt_request &= ~CPU_INTERRUPT_EXIT;
kvm_main_loop_wait(env, 0);
- if (info->reload_regs) {
- info->reload_regs = 0;
- if (env->cpu_index == 0) /* ap needs to be placed in INIT */
- kvm_arch_load_regs(env);
- }
}
pthread_mutex_unlock(&qemu_mutex);
return 0;
@@ -467,10 +469,6 @@ int kvm_main_loop(void)
break;
else if (qemu_powerdown_requested())
qemu_system_powerdown();
- else if (qemu_reset_requested()) {
- pthread_kill(vcpu_info[0].thread, SIG_IPI);
- qemu_kvm_reset_requested = 1;
- }
pthread_mutex_unlock(&qemu_mutex);
}

Index: b/qemu/qemu-kvm-ia64.c
===================================================================
--- a/qemu/qemu-kvm-ia64.c
+++ b/qemu/qemu-kvm-ia64.c
@@ -61,3 +61,7 @@ int kvm_arch_try_push_interrupts(void *o
void kvm_arch_update_regs_for_sipi(CPUState *env)
{
}
+
+void kvm_arch_cpu_reset(CPUState *env)
+{
+}
Index: b/qemu/qemu-kvm-powerpc.c
===================================================================
--- a/qemu/qemu-kvm-powerpc.c
+++ b/qemu/qemu-kvm-powerpc.c
@@ -213,3 +213,7 @@ int handle_powerpc_dcr_write(int vcpu, u

return 0; /* XXX ignore failed DCR ops */
}
+
+void kvm_arch_cpu_reset(CPUState *env)
+{
+}
Index: b/qemu/qemu-kvm-x86.c
===================================================================
--- a/qemu/qemu-kvm-x86.c
+++ b/qemu/qemu-kvm-x86.c
@@ -689,3 +689,19 @@ int handle_tpr_access(void *opaque, int
kvm_tpr_access_report(cpu_single_env, rip, is_write);
return 0;
}
+
+void kvm_arch_cpu_reset(CPUState *env)
+{
+ struct kvm_mp_state mp_state = { .mp_state = KVM_MP_STATE_UNINITIALIZED };
+
+ kvm_arch_load_regs(env);
+ if (env->cpu_index != 0) {
+ if (kvm_irqchip_in_kernel(kvm_context))
+ kvm_set_mpstate(kvm_context, env->cpu_index, &mp_state);
+ else {
+ env->interrupt_request &= ~CPU_INTERRUPT_HARD;
+ env->hflags |= HF_HALTED_MASK;
+ env->exception_index = EXCP_HLT;
+ }
+ }
+}
Index: b/qemu/qemu-kvm.h
===================================================================
--- a/qemu/qemu-kvm.h
+++ b/qemu/qemu-kvm.h
@@ -55,6 +55,7 @@ void kvm_arch_post_kvm_run(void *opaque,
int kvm_arch_has_work(CPUState *env);
int kvm_arch_try_push_interrupts(void *opaque);
void kvm_arch_update_regs_for_sipi(CPUState *env);
+void kvm_arch_cpu_reset(CPUState *env);

CPUState *qemu_kvm_cpu_env(int index);

Index: b/qemu/vl.c
===================================================================
--- a/qemu/vl.c
+++ b/qemu/vl.c
@@ -7235,6 +7235,12 @@ void qemu_system_reset(void)

void qemu_system_reset_request(void)
{
+#ifdef USE_KVM
+ if (kvm_allowed && !no_reboot) {
+ qemu_kvm_system_reset_request();
+ return;
+ }
+#endif
if (no_reboot) {
shutdown_requested = 1;
} else {
@@ -7242,11 +7248,6 @@ void qemu_system_reset_request(void)
}
if (cpu_single_env)
cpu_interrupt(cpu_single_env, CPU_INTERRUPT_EXIT);
-#ifdef USE_KVM
- if (kvm_allowed)
- if (!no_reboot)
- qemu_kvm_system_reset_request();
-#endif
}

void qemu_system_shutdown_request(void)