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Fri, 08 Aug 2025 11:59:16 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFCM/Pp9WgCSSnWFP5mPwLStDTtNjyCCdnYpR+9+Fr6gKo4jSfZBboHQsaMThahH/+9rZYutQ== X-Received: by 2002:a05:600c:3b1b:b0:459:e39e:e5a5 with SMTP id 5b1f17b1804b1-459f51a7fbamr37300105e9.5.1754679556314; Fri, 08 Aug 2025 11:59:16 -0700 (PDT) From: Paolo Bonzini To: qemu-devel@nongnu.org Cc: imammedo@redhat.com, richard.henderson@linaro.org, peterx@redhat.com Subject: [PATCH 3/8] accel: use atomic accesses for exit_request Date: Fri, 8 Aug 2025 20:59:00 +0200 Message-ID: <20250808185905.62776-4-pbonzini@redhat.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250808185905.62776-1-pbonzini@redhat.com> References: <20250808185905.62776-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=pbonzini@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_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1754679674957116600 Content-Type: text/plain; charset="utf-8" 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. Signed-off-by: Paolo Bonzini Reviewed-by: Peter Xu Reviewed-by: Philippe Mathieu-Daud=C3=A9 Reviewed-by: Richard Henderson --- 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 | 2 +- target/i386/nvmm/nvmm-accel-ops.c | 2 +- target/i386/nvmm/nvmm-all.c | 2 +- target/i386/whpx/whpx-all.c | 6 +++--- 7 files changed, 12 insertions(+), 12 deletions(-) diff --git a/accel/tcg/tcg-accel-ops-mttcg.c b/accel/tcg/tcg-accel-ops-mttc= g.c index 337b993d3da..39237421757 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, 1); =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..c06f3beef2e 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, 1); =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 oka= y. */ 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..03a62b047b3 100644 --- a/hw/ppc/spapr_hcall.c +++ b/hw/ppc/spapr_hcall.c @@ -509,7 +509,7 @@ static target_ulong h_cede(PowerPCCPU *cpu, SpaprMachin= eState *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, 1); 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, 1); ppc_maybe_interrupt(&cpu->env); =20 return H_SUCCESS; @@ -624,7 +624,7 @@ static target_ulong h_confer(PowerPCCPU *cpu, SpaprMach= ineState *spapr, } =20 cs->exception_index =3D EXCP_YIELD; - cs->exit_request =3D 1; + qatomic_set(&cs->exit_request, 1); cpu_loop_exit(cs); =20 return H_SUCCESS; diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c index 306430a0521..867eabc6969 100644 --- a/target/i386/kvm/kvm.c +++ b/target/i386/kvm/kvm.c @@ -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, 1); 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-acce= l-ops.c index 3799260bbde..3658a583bc8 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, 1); cpus_kick_thread(cpu); } =20 diff --git a/target/i386/nvmm/nvmm-all.c b/target/i386/nvmm/nvmm-all.c index a5e3485c1f8..d2d90f38976 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, 1); } =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 9f88e368d4d..9b07716121a 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, 1); } if (cpu_test_interrupt(cpu, CPU_INTERRUPT_TPR)) { - cpu->exit_request =3D 1; + qatomic_set(&cpu->exit_request, 1); } } =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, 1); reg_names[reg_count] =3D WHvX64RegisterCr8; reg_count +=3D 1; } --=20 2.50.1