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Re: [Qemu-devel] [PATCH v1] cpus: make pause_all_cpus() play with SMP on
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v1] cpus: make pause_all_cpus() play with SMP on single threaded TCG |
Date: |
Mon, 11 Dec 2017 17:24:20 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 |
On 29/11/2017 20:12, David Hildenbrand wrote:
> pause_all_cpus() is sometimes called from a VCPU thread (e.g. s390x
> during special reset). It cannot deal with multiple VCPUs per Thread
> (single threaded TCG) yet.
>
> Booting an s390x guest with -smp 2 and single threaded TCG from disk
> currently fails. The DIAG 308 will issue a pause_all_cpus() and wait
> forever for the CPUs to actually stop. But it is waiting for itself.
>
> So let's stop all VCPUs belonging to the current thread. Factor out
> stopping of a VCPU.
>
> Signed-off-by: David Hildenbrand <address@hidden>
> ---
> cpus.c | 32 +++++++++++++++++++-------------
> 1 file changed, 19 insertions(+), 13 deletions(-)
>
> diff --git a/cpus.c b/cpus.c
> index 114c29b6a0..3740c4db62 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -1057,13 +1057,22 @@ static void qemu_tcg_destroy_vcpu(CPUState *cpu)
> {
> }
>
> +static void qemu_cpu_stop(CPUState *cpu, bool exit)
> +{
> + g_assert(qemu_cpu_is_self(cpu));
> + cpu->stop = false;
> + cpu->stopped = true;
> + if (exit) {
> + cpu_exit(cpu);
> + }
> + qemu_cond_broadcast(&qemu_pause_cond);
> +}
> +
> static void qemu_wait_io_event_common(CPUState *cpu)
> {
> atomic_mb_set(&cpu->thread_kicked, false);
> if (cpu->stop) {
> - cpu->stop = false;
> - cpu->stopped = true;
> - qemu_cond_broadcast(&qemu_pause_cond);
> + qemu_cpu_stop(cpu, false);
> }
> process_queued_cpu_work(cpu);
> }
> @@ -1610,12 +1619,12 @@ void pause_all_vcpus(void)
>
> qemu_clock_enable(QEMU_CLOCK_VIRTUAL, false);
> CPU_FOREACH(cpu) {
> - cpu->stop = true;
> - qemu_cpu_kick(cpu);
> - }
> -
> - if (qemu_in_vcpu_thread()) {
> - cpu_stop_current();
> + if (qemu_cpu_is_self(cpu)) {
> + qemu_cpu_stop(cpu, true);
> + } else {
> + cpu->stop = true;
> + qemu_cpu_kick(cpu);
> + }
> }
>
> while (!all_vcpus_paused()) {
> @@ -1799,10 +1808,7 @@ void qemu_init_vcpu(CPUState *cpu)
> void cpu_stop_current(void)
> {
> if (current_cpu) {
> - current_cpu->stop = false;
> - current_cpu->stopped = true;
> - cpu_exit(current_cpu);
> - qemu_cond_broadcast(&qemu_pause_cond);
> + qemu_cpu_stop(current_cpu, true);
> }
> }
This function is not needed anymore, because vm_stop can just call
qemu_cpu_stop. Does the following squash look fine to you?
diff --git a/cpus.c b/cpus.c
index 83700c1716..a65591c183 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1057,14 +1057,11 @@ static void qemu_tcg_destroy_vcpu(CPUState *cpu)
{
}
-static void qemu_cpu_stop(CPUState *cpu, bool exit)
+static void qemu_cpu_stop(CPUState *cpu)
{
g_assert(qemu_cpu_is_self(cpu));
cpu->stop = false;
cpu->stopped = true;
- if (exit) {
- cpu_exit(cpu);
- }
qemu_cond_broadcast(&qemu_pause_cond);
}
@@ -1072,7 +1069,7 @@ static void qemu_wait_io_event_common(CPUState *cpu)
{
atomic_mb_set(&cpu->thread_kicked, false);
if (cpu->stop) {
- qemu_cpu_stop(cpu, false);
+ qemu_cpu_stop(cpu);
}
process_queued_cpu_work(cpu);
}
@@ -1620,7 +1617,8 @@ void pause_all_vcpus(void)
qemu_clock_enable(QEMU_CLOCK_VIRTUAL, false);
CPU_FOREACH(cpu) {
if (qemu_cpu_is_self(cpu)) {
- qemu_cpu_stop(cpu, true);
+ qemu_cpu_stop(cpu);
+ cpu_exit(cpu);
} else {
cpu->stop = true;
qemu_cpu_kick(cpu);
@@ -1802,13 +1800,6 @@ void qemu_init_vcpu(CPUState *cpu)
}
}
-void cpu_stop_current(void)
-{
- if (current_cpu) {
- qemu_cpu_stop(current_cpu, true);
- }
-}
-
int vm_stop(RunState state)
{
if (qemu_in_vcpu_thread()) {
@@ -1818,7 +1809,8 @@ int vm_stop(RunState state)
* FIXME: should not return to device code in case
* vm_stop() has been requested.
*/
- cpu_stop_current();
+ qemu_cpu_stop(current_cpu);
+ cpu_exit(current_cpu);
return 0;
}
- Re: [Qemu-devel] [PATCH v1] cpus: make pause_all_cpus() play with SMP on single threaded TCG,
Paolo Bonzini <=