This is part of a series of changes to remove the implied BQL from the common code of cpu_handle_interrupt and cpu_handle_exception. As part of removing the implied BQL from the common code, we are pushing the BQL holding down into the per-arch implementation functions of do_interrupt and cpu_exec_interrupt.
The purpose of this set of changes is to set the groundwork so that an arch could move towards removing the BQL from the cpu_handle_interrupt/exception paths. This approach was suggested by Paolo Bonzini. For reference, here are two key posts in the discussion, explaining the reasoning/benefits of this approach. https://lists.gnu.org/archive/html/qemu-devel/2020-07/msg08731.html https://lists.gnu.org/archive/html/qemu-devel/2020-08/msg00044.html Signed-off-by: Robert Foley <robert.fo...@linaro.org> --- target/sparc/cpu.c | 3 +++ target/sparc/int32_helper.c | 13 ++++++++++++- 2 files changed, 15 insertions(+), 1 deletion(-) diff --git a/target/sparc/cpu.c b/target/sparc/cpu.c index 20c7c0c434..13b5a038e8 100644 --- a/target/sparc/cpu.c +++ b/target/sparc/cpu.c @@ -79,6 +79,7 @@ static void sparc_cpu_reset(DeviceState *dev) static bool sparc_cpu_exec_interrupt(CPUState *cs, int interrupt_request) { + qemu_mutex_lock_iothread(); if (interrupt_request & CPU_INTERRUPT_HARD) { SPARCCPU *cpu = SPARC_CPU(cs); CPUSPARCState *env = &cpu->env; @@ -90,10 +91,12 @@ static bool sparc_cpu_exec_interrupt(CPUState *cs, int interrupt_request) if (type != TT_EXTINT || cpu_pil_allowed(env, pil)) { cs->exception_index = env->interrupt_index; sparc_cpu_do_interrupt(cs); + qemu_mutex_unlock_iothread(); return true; } } } + qemu_mutex_unlock_iothread(); return false; } diff --git a/target/sparc/int32_helper.c b/target/sparc/int32_helper.c index 9a71e1abd8..3940e945ed 100644 --- a/target/sparc/int32_helper.c +++ b/target/sparc/int32_helper.c @@ -69,7 +69,12 @@ void sparc_cpu_do_interrupt(CPUState *cs) { SPARCCPU *cpu = SPARC_CPU(cs); CPUSPARCState *env = &cpu->env; - int cwp, intno = cs->exception_index; + int cwp, intno; + bool bql = !qemu_mutex_iothread_locked(); + if (bql) { + qemu_mutex_lock_iothread(); + } + intno = cs->exception_index; /* Compute PSR before exposing state. */ if (env->cc_op != CC_OP_FLAGS) { @@ -115,6 +120,9 @@ void sparc_cpu_do_interrupt(CPUState *cs) "Error state", cs->exception_index, excp_name_str(cs->exception_index)); } + if (bql) { + qemu_mutex_unlock_iothread(); + } return; } #endif @@ -136,6 +144,9 @@ void sparc_cpu_do_interrupt(CPUState *cs) env->qemu_irq_ack(env, env->irq_manager, intno); } #endif + if (bql) { + qemu_mutex_unlock_iothread(); + } } #if !defined(CONFIG_USER_ONLY) -- 2.17.1