Re: [Qemu-devel] Re: [6684] Fix "info registers" under kvm.

[Avi Kivity <avi@redhat.com>]

Anthony Liguori wrote:
>
> In the case of save/load registers, I'd prefer wrapper functions like:
>
> cpu_state_update(CPUState *env, int is_dirty)
>
> That could be hooked by something like Xen.  The implementation would be:
>
> static void cpu_state_update(CPUState *env, int is_dirty)
> {
>    if (kvm_enabled()) {
>        if (is_dirty)
>           kvm_arch_save_registers(env);
>        else
>           kvm_arch_load_registers(env);
>    }
> } 

That reduces readability IMO (boolean parameters do that, as well as a 
function where the direction of data movement isn't clear).

But we could keep dirty in the environment, and do everything automatically.

random qemu code:
  cpu_state_sync(env);
  // read registers
  // write registers
  cpu_state_dirty(env);

kvm arch code:
  if (env->registers_dirty) {
      copy registers to kernel
      env->registers_dirty = 0;
  }

The kernel code does similar things for registers which can be either in 
memory or in the vmcs; it uses accessors so cpu_state_sync() and 
cpu_state_dirty() aren't needed;

-- 
error compiling committee.c: too many arguments to function