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x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=170.10.133.124; envelope-from=imammedo@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Fri, 29 Aug 2025 17:31:07 +0200 Paolo Bonzini wrote: > 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. >=20 > While at it, change the source argument from int ("1") to bool ("true"). >=20 > Reviewed-by: Richard Henderson > Reviewed-by: Philippe Mathieu-Daud=C3=A9 > Reviewed-by: Peter Xu > Signed-off-by: Paolo Bonzini Reviewed-by: Igor Mammedov > --- > include/hw/core/cpu.h | 9 +++++++++ > accel/kvm/kvm-all.c | 2 +- > 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 | 6 +++--- > target/i386/nvmm/nvmm-accel-ops.c | 2 +- > target/i386/nvmm/nvmm-all.c | 2 +- > target/i386/whpx/whpx-all.c | 6 +++--- > 9 files changed, 24 insertions(+), 15 deletions(-) >=20 > diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h > index 8b57bcd92c9..338757e5254 100644 > --- a/include/hw/core/cpu.h > +++ b/include/hw/core/cpu.h > @@ -422,6 +422,15 @@ struct qemu_work_item; > * valid under cpu_list_lock. > * @created: Indicates whether the CPU thread has been successfully crea= ted. > * @halt_cond: condition variable sleeping threads can wait on. > + * @exit_request: Another thread requests the CPU to call qemu_wait_io_e= vent(). > + * Should be read only by CPU thread with load-acquire, to synchronize= with > + * other threads' store-release operation. > + * > + * In some cases, accelerator-specific code will write exit_request fr= om > + * within the same thread, to "bump" the effect of qemu_cpu_kick() to > + * the one provided by cpu_exit(), especially when processing interrupt > + * flags. In this case, the write and read happen in the same thread > + * and the write therefore can use qemu_atomic_set(). > * @interrupt_request: Indicates a pending interrupt request. > * Only used by system emulation. > * @halted: Nonzero if the CPU is in suspended state. > diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c > index bd9e5e3886d..e4167d94b4f 100644 > --- a/accel/kvm/kvm-all.c > +++ b/accel/kvm/kvm-all.c > @@ -3730,7 +3730,7 @@ int kvm_on_sigbus_vcpu(CPUState *cpu, int code, voi= d *addr) > have_sigbus_pending =3D true; > pending_sigbus_addr =3D addr; > pending_sigbus_code =3D code; > - qatomic_set(&cpu->exit_request, 1); > + qatomic_set(&cpu->exit_request, true); > return 0; > #else > return 1; > diff --git a/accel/tcg/tcg-accel-ops-mttcg.c b/accel/tcg/tcg-accel-ops-mt= tcg.c > index 337b993d3da..b12b7a36b5d 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); > =20 > /* process any pending work */ > - cpu->exit_request =3D 1; > + qatomic_set(&cpu->exit_request, true); > =20 > 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..c2468d15d4f 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 =3D first_cpu; > =20 > /* process any pending work */ > - cpu->exit_request =3D 1; > + qatomic_set(&cpu->exit_request, true); > =20 > 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 o= kay. */ > qatomic_set(&rr_current_cpu, NULL); > =20 > - if (cpu && cpu->exit_request) { > + if (cpu && qatomic_read(&cpu->exit_request)) { > qatomic_set_mb(&cpu->exit_request, 0); > } > =20 > diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c > index 1e936f35e44..51875e32a09 100644 > --- a/hw/ppc/spapr_hcall.c > +++ b/hw/ppc/spapr_hcall.c > @@ -509,7 +509,7 @@ static target_ulong h_cede(PowerPCCPU *cpu, SpaprMach= ineState *spapr, > if (!cpu_has_work(cs)) { > cs->halted =3D 1; > cs->exception_index =3D EXCP_HLT; > - cs->exit_request =3D 1; > + qatomic_set(&cs->exit_request, true); > ppc_maybe_interrupt(env); > } > =20 > @@ -531,7 +531,7 @@ static target_ulong h_confer_self(PowerPCCPU *cpu) > } > cs->halted =3D 1; > cs->exception_index =3D EXCP_HALTED; > - cs->exit_request =3D 1; > + qatomic_set(&cs->exit_request, true); > ppc_maybe_interrupt(&cpu->env); > =20 > return H_SUCCESS; > @@ -624,7 +624,7 @@ static target_ulong h_confer(PowerPCCPU *cpu, SpaprMa= chineState *spapr, > } > =20 > cs->exception_index =3D EXCP_YIELD; > - cs->exit_request =3D 1; > + qatomic_set(&cs->exit_request, true); > cpu_loop_exit(cs); > =20 > return H_SUCCESS; > diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c > index 8420c4090ef..34e74f24470 100644 > --- a/target/i386/kvm/kvm.c > +++ b/target/i386/kvm/kvm.c > @@ -5486,10 +5486,10 @@ void kvm_arch_pre_run(CPUState *cpu, struct kvm_r= un *run) > if (cpu_test_interrupt(cpu, CPU_INTERRUPT_INIT | CPU_INTERRUPT_TPR))= { > if (cpu_test_interrupt(cpu, CPU_INTERRUPT_INIT) && > !(env->hflags & HF_SMM_MASK)) { > - qatomic_set(&cpu->exit_request, 1); > + qatomic_set(&cpu->exit_request, true); > } > if (cpu_test_interrupt(cpu, CPU_INTERRUPT_TPR)) { > - qatomic_set(&cpu->exit_request, 1); > + qatomic_set(&cpu->exit_request, true); > } > } > =20 > @@ -5604,7 +5604,7 @@ int kvm_arch_process_async_events(CPUState *cs) > if (env->exception_nr =3D=3D EXCP08_DBLE) { > /* this means triple fault */ > qemu_system_reset_request(SHUTDOWN_CAUSE_GUEST_RESET); > - cs->exit_request =3D 1; > + qatomic_set(&cs->exit_request, true); > 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-ac= cel-ops.c > index 3799260bbde..86869f133e9 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 =3D 1; > + qatomic_set(&cpu->exit_request, true); > cpus_kick_thread(cpu); > } > =20 > diff --git a/target/i386/nvmm/nvmm-all.c b/target/i386/nvmm/nvmm-all.c > index 10bd51d9b59..7e36c42fbb4 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 =3D 1; > + qatomic_set(&cpu->exit_request, true); > } > =20 > 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 2106c29c3a0..00fb7e23100 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 =3D 1; > + qatomic_set(&cpu->exit_request, true); > } > if (cpu_test_interrupt(cpu, CPU_INTERRUPT_TPR)) { > - cpu->exit_request =3D 1; > + qatomic_set(&cpu->exit_request, true); > } > } > =20 > @@ -1539,7 +1539,7 @@ static void whpx_vcpu_pre_run(CPUState *cpu) > if (tpr !=3D vcpu->tpr) { > vcpu->tpr =3D tpr; > reg_values[reg_count].Reg64 =3D tpr; > - cpu->exit_request =3D 1; > + qatomic_set(&cpu->exit_request, true); > reg_names[reg_count] =3D WHvX64RegisterCr8; > reg_count +=3D 1; > }