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/avr/helper.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/target/avr/helper.c b/target/avr/helper.c index d96d14372b..f0d625c195 100644 --- a/target/avr/helper.c +++ b/target/avr/helper.c @@ -30,6 +30,7 @@ bool avr_cpu_exec_interrupt(CPUState *cs, int interrupt_request) CPUClass *cc = CPU_GET_CLASS(cs); AVRCPU *cpu = AVR_CPU(cs); CPUAVRState *env = &cpu->env; + qemu_mutex_lock_iothread(); if (interrupt_request & CPU_INTERRUPT_RESET) { if (cpu_interrupts_enabled(env)) { @@ -53,6 +54,7 @@ bool avr_cpu_exec_interrupt(CPUState *cs, int interrupt_request) ret = true; } } + qemu_mutex_unlock_iothread(); return ret; } @@ -61,10 +63,15 @@ void avr_cpu_do_interrupt(CPUState *cs) AVRCPU *cpu = AVR_CPU(cs); CPUAVRState *env = &cpu->env; - uint32_t ret = env->pc_w; + uint32_t ret; int vector = 0; int size = avr_feature(env, AVR_FEATURE_JMP_CALL) ? 2 : 1; int base = 0; + bool bql = !qemu_mutex_iothread_locked(); + if (bql) { + qemu_mutex_lock_iothread(); + } + ret = env->pc_w; if (cs->exception_index == EXCP_RESET) { vector = 0; @@ -87,6 +94,9 @@ void avr_cpu_do_interrupt(CPUState *cs) env->sregI = 0; /* clear Global Interrupt Flag */ cs->exception_index = -1; + if (bql) { + qemu_mutex_unlock_iothread(); + } } int avr_cpu_memory_rw_debug(CPUState *cs, vaddr addr, uint8_t *buf, -- 2.17.1
