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Re: [Qemu-devel] [RFC PATCH v5 07/31] icount: implement icount requestin


From: Pavel Dovgaluk
Subject: Re: [Qemu-devel] [RFC PATCH v5 07/31] icount: implement icount requesting
Date: Fri, 5 Dec 2014 15:59:01 +0300

> From: Paolo Bonzini [mailto:address@hidden
> On 05/12/2014 11:55, Pavel Dovgaluk wrote:
> >> >
> >> > And why is can_do_io zero? :)  Is the fix to move the place where
> >> > can_do_io becomes nonzero?
> > can_do_io is set by gen_io_start function.
> > As I understand, it is used to protect determinism in icount mode,
> > because it allows non-deterministic (port io, raising interrupt)
> > operations only at the end of the translation blocks.
> > When someone tries to use MMIO in the middle of TB, that TB is
> > recompiled to place this instruction at the end of the block.
> >
> > Do you mean that we can set can_do_io before execution of the block
> > and reset it at the beginning of the execution?
> 
> Yes, we could try setting it after execution of the block and clearing
> it afterwards.  Peter knows that part of icount better though (I know
> mostly the timer/warping parts).

Ok, how about these changes?

diff --git a/cpu-exec.c b/cpu-exec.c
index f52f292..88675ca 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -168,7 +168,9 @@ static inline tcg_target_ulong cpu_tb_exec(CPUState *cpu, 
uint8_t *tb_ptr)
     }
 #endif /* DEBUG_DISAS */
 
+    cpu->can_do_io = 0;
     next_tb = tcg_qemu_tb_exec(env, tb_ptr);
+    cpu->can_do_io = 1;
     trace_exec_tb_exit((void *) (next_tb & ~TB_EXIT_MASK),
                        next_tb & TB_EXIT_MASK);
 
@@ -548,6 +550,7 @@ int cpu_exec(CPUArchState *env)
             cpu = current_cpu;
             env = cpu->env_ptr;
             cc = CPU_GET_CLASS(cpu);
+            cpu->can_do_io = 1;
 #ifdef TARGET_I386
             x86_cpu = X86_CPU(cpu);
 #endif
diff --git a/cpus.c b/cpus.c
index 0c33458..7a45a51 100644
--- a/cpus.c
+++ b/cpus.c
@@ -934,6 +934,7 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
     qemu_mutex_lock(&qemu_global_mutex);
     qemu_thread_get_self(cpu->thread);
     cpu->thread_id = qemu_get_thread_id();
+    cpu->can_do_io = 1;
     current_cpu = cpu;
 
     r = kvm_init_vcpu(cpu);
@@ -974,6 +975,7 @@ static void *qemu_dummy_cpu_thread_fn(void *arg)
     qemu_mutex_lock_iothread();
     qemu_thread_get_self(cpu->thread);
     cpu->thread_id = qemu_get_thread_id();
+    cpu->can_do_io = 1;
 
     sigemptyset(&waitset);
     sigaddset(&waitset, SIG_IPI);
@@ -1016,6 +1018,7 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
     CPU_FOREACH(cpu) {
         cpu->thread_id = qemu_get_thread_id();
         cpu->created = true;
+        cpu->can_do_io = 1;
     }
     qemu_cond_signal(&qemu_cpu_cond);





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