[PATCH v1 14/21] target/ppc: add BQL to do_interrupt and cpu_exec_interrupt

[Robert Foley]

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.foley@linaro.org>
---
 target/ppc/excp_helper.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
index bf9e1e27e9..4530230d65 100644
--- a/target/ppc/excp_helper.c
+++ b/target/ppc/excp_helper.c
@@ -870,7 +870,9 @@ void ppc_cpu_do_interrupt(CPUState *cs)
     PowerPCCPU *cpu = POWERPC_CPU(cs);
     CPUPPCState *env = &cpu->env;
 
+    qemu_mutex_lock_iothread();
     powerpc_excp(cpu, env->excp_model, cs->exception_index);
+    qemu_mutex_unlock_iothread();
 }
 
 static void ppc_hw_interrupt(CPUPPCState *env)
@@ -1056,14 +1058,17 @@ bool ppc_cpu_exec_interrupt(CPUState *cs, int 
interrupt_request)
 {
     PowerPCCPU *cpu = POWERPC_CPU(cs);
     CPUPPCState *env = &cpu->env;
+    qemu_mutex_lock_iothread();
 
     if (interrupt_request & CPU_INTERRUPT_HARD) {
         ppc_hw_interrupt(env);
         if (env->pending_interrupts == 0) {
             cpu_reset_interrupt(cs, CPU_INTERRUPT_HARD);
         }
+        qemu_mutex_unlock_iothread();
         return true;
     }
+    qemu_mutex_unlock_iothread();
     return false;
 }
 
-- 
2.17.1