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/riscv/cpu_helper.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c index 75d2ae3434..5050802e95 100644 --- a/target/riscv/cpu_helper.c +++ b/target/riscv/cpu_helper.c @@ -80,14 +80,17 @@ bool riscv_cpu_exec_interrupt(CPUState *cs, int interrupt_request) { #if !defined(CONFIG_USER_ONLY) if (interrupt_request & CPU_INTERRUPT_HARD) { + qemu_mutex_lock_iothread(); RISCVCPU *cpu = RISCV_CPU(cs); CPURISCVState *env = &cpu->env; int interruptno = riscv_cpu_local_irq_pending(env); if (interruptno >= 0) { cs->exception_index = RISCV_EXCP_INT_FLAG | interruptno; riscv_cpu_do_interrupt(cs); + qemu_mutex_unlock_iothread(); return true; } + qemu_mutex_unlock_iothread(); } #endif return false; @@ -822,6 +825,10 @@ bool riscv_cpu_tlb_fill(CPUState *cs, vaddr address, int size, */ void riscv_cpu_do_interrupt(CPUState *cs) { + bool bql = !qemu_mutex_iothread_locked(); + if (bql) { + qemu_mutex_lock_iothread(); + } #if !defined(CONFIG_USER_ONLY) RISCVCPU *cpu = RISCV_CPU(cs); @@ -982,4 +989,7 @@ void riscv_cpu_do_interrupt(CPUState *cs) #endif cs->exception_index = EXCP_NONE; /* mark handled to qemu */ + if (bql) { + qemu_mutex_unlock_iothread(); + } } -- 2.17.1
