[PATCH v1 20/21] target/unicore32: 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/unicore32/helper.c  | 3 +++
 target/unicore32/softmmu.c | 7 +++++++
 2 files changed, 10 insertions(+)

diff --git a/target/unicore32/helper.c b/target/unicore32/helper.c
index 54c26871fe..d79284d224 100644
--- a/target/unicore32/helper.c
+++ b/target/unicore32/helper.c
@@ -169,6 +169,7 @@ void helper_cp1_putc(target_ulong regval)
 
 bool uc32_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
 {
+    qemu_mutex_lock_iothread();
     if (interrupt_request & CPU_INTERRUPT_HARD) {
         UniCore32CPU *cpu = UNICORE32_CPU(cs);
         CPUUniCore32State *env = &cpu->env;
@@ -176,8 +177,10 @@ bool uc32_cpu_exec_interrupt(CPUState *cs, int 
interrupt_request)
         if (!(env->uncached_asr & ASR_I)) {
             cs->exception_index = UC32_EXCP_INTR;
             uc32_cpu_do_interrupt(cs);
+            qemu_mutex_unlock_iothread();
             return true;
         }
     }
+    qemu_mutex_unlock_iothread();
     return false;
 }
diff --git a/target/unicore32/softmmu.c b/target/unicore32/softmmu.c
index 9660bd2a27..ca9b92aad0 100644
--- a/target/unicore32/softmmu.c
+++ b/target/unicore32/softmmu.c
@@ -81,6 +81,10 @@ void uc32_cpu_do_interrupt(CPUState *cs)
     CPUUniCore32State *env = &cpu->env;
     uint32_t addr;
     int new_mode;
+    bool bql = !qemu_mutex_iothread_locked();
+    if (bql) {
+        qemu_mutex_lock_iothread();
+    }
 
     switch (cs->exception_index) {
     case UC32_EXCP_PRIV:
@@ -118,6 +122,9 @@ void uc32_cpu_do_interrupt(CPUState *cs)
     env->regs[30] = env->regs[31];
     env->regs[31] = addr;
     cpu_interrupt_request_or(cs, CPU_INTERRUPT_EXITTB);
+    if (bql) {
+        qemu_mutex_unlock_iothread();
+    }
 }
 
 static int get_phys_addr_ucv2(CPUUniCore32State *env, uint32_t address,
-- 
2.17.1