Re: [PATCH] accel: Do not set CPUState::can_do_io in non-TCG accels

Richard Henderson <richard.henderson@xxxxxxxxxx> · Thu, 30 Nov 2023 07:51:14 -0600

On 11/29/23 14:50, Philippe Mathieu-Daudé wrote:
'can_do_io' is specific to TCG. Having it set in non-TCG
code is confusing, so remove it from QTest / HVF / KVM.

Signed-off-by: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>
---
  accel/dummy-cpus.c        | 1 -
  accel/hvf/hvf-accel-ops.c | 1 -
  accel/kvm/kvm-accel-ops.c | 1 -
  3 files changed, 3 deletions(-)

diff --git a/accel/dummy-cpus.c b/accel/dummy-cpus.c
index b75c919ac3..1005ec6f56 100644
--- a/accel/dummy-cpus.c
+++ b/accel/dummy-cpus.c
@@ -27,7 +27,6 @@ static void *dummy_cpu_thread_fn(void *arg)
      qemu_mutex_lock_iothread();
      qemu_thread_get_self(cpu->thread);
      cpu->thread_id = qemu_get_thread_id();
-    cpu->neg.can_do_io = true;
      current_cpu = cpu;

I expect this is ok...

When I was moving this variable around just recently, 464dacf6, I wondered about these 
other settings, and I wondered if they used to be required for implementing some i/o on 
behalf of hw accel.  Something that has now been factored out to e.g. kvm_handle_io, which 
now uses address_space_rw directly.

I see 3 reads of can_do_io: accel/tcg/{cputlb.c, icount-common.c} and system/watchpoint.c. 
 The final one is nested within replay_running_debug(), which implies icount and tcg.

Reviewed-by: Richard Henderson <richard.henderson@xxxxxxxxxx>


r~

  
  #ifndef _WIN32
diff --git a/accel/hvf/hvf-accel-ops.c b/accel/hvf/hvf-accel-ops.c
index abe7adf7ee..2bba54cf70 100644
--- a/accel/hvf/hvf-accel-ops.c
+++ b/accel/hvf/hvf-accel-ops.c
@@ -428,7 +428,6 @@ static void *hvf_cpu_thread_fn(void *arg)
      qemu_thread_get_self(cpu->thread);
  
      cpu->thread_id = qemu_get_thread_id();
-    cpu->neg.can_do_io = true;
      current_cpu = cpu;
  
      hvf_init_vcpu(cpu);
diff --git a/accel/kvm/kvm-accel-ops.c b/accel/kvm/kvm-accel-ops.c
index 6195150a0b..f273f415db 100644
--- a/accel/kvm/kvm-accel-ops.c
+++ b/accel/kvm/kvm-accel-ops.c
@@ -36,7 +36,6 @@ static void *kvm_vcpu_thread_fn(void *arg)
      qemu_mutex_lock_iothread();
      qemu_thread_get_self(cpu->thread);
      cpu->thread_id = qemu_get_thread_id();
-    cpu->neg.can_do_io = true;
      current_cpu = cpu;
  
      r = kvm_init_vcpu(cpu, &error_fatal);








