On Fri, 29 Aug 2025 17:31:14 +0200 Paolo Bonzini <[email protected]> wrote:
> There is no reason for some accelerators to use qemu_wait_io_event_common > (which is separated from qemu_wait_io_event() specifically for round > robin). They can also check for events directly on the first pass through > the loop, instead of setting cpu->exit_request to true. > > Signed-off-by: Paolo Bonzini <[email protected]> Reviewed-by: Igor Mammedov <[email protected]> > --- > accel/dummy-cpus.c | 2 +- > accel/hvf/hvf-accel-ops.c | 2 +- > accel/kvm/kvm-accel-ops.c | 3 ++- > accel/tcg/tcg-accel-ops-mttcg.c | 7 ++--- > accel/tcg/tcg-accel-ops-rr.c | 43 ++++++++++++++----------------- > target/i386/nvmm/nvmm-accel-ops.c | 6 ++--- > target/i386/whpx/whpx-accel-ops.c | 6 ++--- > 7 files changed, 30 insertions(+), 39 deletions(-) > > diff --git a/accel/dummy-cpus.c b/accel/dummy-cpus.c > index 03cfc0fa01e..1f74c727c42 100644 > --- a/accel/dummy-cpus.c > +++ b/accel/dummy-cpus.c > @@ -43,6 +43,7 @@ static void *dummy_cpu_thread_fn(void *arg) > qemu_guest_random_seed_thread_part2(cpu->random_seed); > > do { > + qemu_wait_io_event(cpu); > bql_unlock(); > #ifndef _WIN32 > do { > @@ -57,7 +58,6 @@ static void *dummy_cpu_thread_fn(void *arg) > qemu_sem_wait(&cpu->sem); > #endif > bql_lock(); > - qemu_wait_io_event(cpu); > } while (!cpu->unplug); > > bql_unlock(); > diff --git a/accel/hvf/hvf-accel-ops.c b/accel/hvf/hvf-accel-ops.c > index d488d6afbac..4ba3e40831f 100644 > --- a/accel/hvf/hvf-accel-ops.c > +++ b/accel/hvf/hvf-accel-ops.c > @@ -192,13 +192,13 @@ static void *hvf_cpu_thread_fn(void *arg) > qemu_guest_random_seed_thread_part2(cpu->random_seed); > > do { > + qemu_wait_io_event(cpu); > if (cpu_can_run(cpu)) { > r = hvf_vcpu_exec(cpu); > if (r == EXCP_DEBUG) { > cpu_handle_guest_debug(cpu); > } > } > - qemu_wait_io_event(cpu); > } while (!cpu->unplug || cpu_can_run(cpu)); > > hvf_vcpu_destroy(cpu); > diff --git a/accel/kvm/kvm-accel-ops.c b/accel/kvm/kvm-accel-ops.c > index b709187c7d7..80f0141a8a6 100644 > --- a/accel/kvm/kvm-accel-ops.c > +++ b/accel/kvm/kvm-accel-ops.c > @@ -47,13 +47,14 @@ static void *kvm_vcpu_thread_fn(void *arg) > qemu_guest_random_seed_thread_part2(cpu->random_seed); > > do { > + qemu_wait_io_event(cpu); > + > if (cpu_can_run(cpu)) { > r = kvm_cpu_exec(cpu); > if (r == EXCP_DEBUG) { > cpu_handle_guest_debug(cpu); > } > } > - qemu_wait_io_event(cpu); > } while (!cpu->unplug || cpu_can_run(cpu)); > > kvm_destroy_vcpu(cpu); > diff --git a/accel/tcg/tcg-accel-ops-mttcg.c b/accel/tcg/tcg-accel-ops-mttcg.c > index 1148ebcaae5..04012900a30 100644 > --- a/accel/tcg/tcg-accel-ops-mttcg.c > +++ b/accel/tcg/tcg-accel-ops-mttcg.c > @@ -84,10 +84,9 @@ static void *mttcg_cpu_thread_fn(void *arg) > cpu_thread_signal_created(cpu); > qemu_guest_random_seed_thread_part2(cpu->random_seed); > > - /* process any pending work */ > - qatomic_set(&cpu->exit_request, true); > - > do { > + qemu_wait_io_event(cpu); > + > if (cpu_can_run(cpu)) { > int r; > bql_unlock(); > @@ -112,8 +111,6 @@ static void *mttcg_cpu_thread_fn(void *arg) > break; > } > } > - > - qemu_wait_io_event(cpu); > } while (!cpu->unplug || cpu_can_run(cpu)); > > tcg_cpu_destroy(cpu); > diff --git a/accel/tcg/tcg-accel-ops-rr.c b/accel/tcg/tcg-accel-ops-rr.c > index e9d291dc391..28897288db7 100644 > --- a/accel/tcg/tcg-accel-ops-rr.c > +++ b/accel/tcg/tcg-accel-ops-rr.c > @@ -211,13 +211,30 @@ static void *rr_cpu_thread_fn(void *arg) > > cpu = first_cpu; > > - /* process any pending work */ > - qatomic_set(&cpu->exit_request, true); > - > while (1) { > /* Only used for icount_enabled() */ > int64_t cpu_budget = 0; > > + if (cpu) { > + /* > + * This could even reset exit_request for all CPUs, but in > practice > + * races between CPU exits and changes to "cpu" are so rare that > + * there's no advantage in doing so. > + */ > + qatomic_set(&cpu->exit_request, false); > + } > + > + if (icount_enabled() && all_cpu_threads_idle()) { > + /* > + * When all cpus are sleeping (e.g in WFI), to avoid a deadlock > + * in the main_loop, wake it up in order to start the warp timer. > + */ > + qemu_notify_event(); > + } > + > + rr_wait_io_event(); > + rr_deal_with_unplugged_cpus(); > + > bql_unlock(); > replay_mutex_lock(); > bql_lock(); > @@ -285,26 +302,6 @@ 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) { > - /* > - * This could even reset exit_request for all CPUs, but in > practice > - * races between CPU exits and changes to "cpu" are so rare that > - * there's no advantage in doing so. > - */ > - qatomic_set(&cpu->exit_request, false); > - } > - > - if (icount_enabled() && all_cpu_threads_idle()) { > - /* > - * When all cpus are sleeping (e.g in WFI), to avoid a deadlock > - * in the main_loop, wake it up in order to start the warp timer. > - */ > - qemu_notify_event(); > - } > - > - rr_wait_io_event(); > - rr_deal_with_unplugged_cpus(); > } > > g_assert_not_reached(); > diff --git a/target/i386/nvmm/nvmm-accel-ops.c > b/target/i386/nvmm/nvmm-accel-ops.c > index 86869f133e9..f51244740d8 100644 > --- a/target/i386/nvmm/nvmm-accel-ops.c > +++ b/target/i386/nvmm/nvmm-accel-ops.c > @@ -42,16 +42,14 @@ static void *qemu_nvmm_cpu_thread_fn(void *arg) > qemu_guest_random_seed_thread_part2(cpu->random_seed); > > do { > + qemu_wait_io_event(cpu); > + > if (cpu_can_run(cpu)) { > r = nvmm_vcpu_exec(cpu); > if (r == EXCP_DEBUG) { > cpu_handle_guest_debug(cpu); > } > } > - while (cpu_thread_is_idle(cpu)) { > - qemu_cond_wait_bql(cpu->halt_cond); > - } > - qemu_wait_io_event_common(cpu); > } while (!cpu->unplug || cpu_can_run(cpu)); > > nvmm_destroy_vcpu(cpu); > diff --git a/target/i386/whpx/whpx-accel-ops.c > b/target/i386/whpx/whpx-accel-ops.c > index da58805b1a6..611eeedeef7 100644 > --- a/target/i386/whpx/whpx-accel-ops.c > +++ b/target/i386/whpx/whpx-accel-ops.c > @@ -42,16 +42,14 @@ static void *whpx_cpu_thread_fn(void *arg) > qemu_guest_random_seed_thread_part2(cpu->random_seed); > > do { > + qemu_wait_io_event(cpu); > + > if (cpu_can_run(cpu)) { > r = whpx_vcpu_exec(cpu); > if (r == EXCP_DEBUG) { > cpu_handle_guest_debug(cpu); > } > } > - while (cpu_thread_is_idle(cpu)) { > - qemu_cond_wait_bql(cpu->halt_cond); > - } > - qemu_wait_io_event_common(cpu); > } while (!cpu->unplug || cpu_can_run(cpu)); > > whpx_destroy_vcpu(cpu);
