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/s390x/excp_helper.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/target/s390x/excp_helper.c b/target/s390x/excp_helper.c index dde7afc2f0..b215b4a4a7 100644 --- a/target/s390x/excp_helper.c +++ b/target/s390x/excp_helper.c @@ -470,7 +470,10 @@ void s390_cpu_do_interrupt(CPUState *cs) S390CPU *cpu = S390_CPU(cs); CPUS390XState *env = &cpu->env; bool stopped = false; - + bool bql = !qemu_mutex_iothread_locked(); + if (bql) { + qemu_mutex_lock_iothread(); + } qemu_log_mask(CPU_LOG_INT, "%s: %d at psw=%" PRIx64 ":%" PRIx64 "\n", __func__, cs->exception_index, env->psw.mask, env->psw.addr); @@ -541,10 +544,14 @@ try_deliver: /* unhalt if we had a WAIT PSW somehwere in our injection chain */ s390_cpu_unhalt(cpu); } + if (bql) { + qemu_mutex_unlock_iothread(); + } } bool s390_cpu_exec_interrupt(CPUState *cs, int interrupt_request) { + qemu_mutex_lock_iothread(); if (interrupt_request & CPU_INTERRUPT_HARD) { S390CPU *cpu = S390_CPU(cs); CPUS390XState *env = &cpu->env; @@ -552,10 +559,12 @@ bool s390_cpu_exec_interrupt(CPUState *cs, int interrupt_request) if (env->ex_value) { /* Execution of the target insn is indivisible from the parent EXECUTE insn. */ + qemu_mutex_unlock_iothread(); return false; } if (s390_cpu_has_int(cpu)) { s390_cpu_do_interrupt(cs); + qemu_mutex_unlock_iothread(); return true; } if (env->psw.mask & PSW_MASK_WAIT) { @@ -564,6 +573,7 @@ bool s390_cpu_exec_interrupt(CPUState *cs, int interrupt_request) cpu_interrupt(CPU(cpu), CPU_INTERRUPT_HALT); } } + qemu_mutex_unlock_iothread(); return false; } -- 2.17.1
