Re: [Qemu-trivial] [Qemu-devel] [PATCH 4/9] cpu/topology: add ARM support for smp machine properties

[Eduardo Habkost]

On Mon, Apr 01, 2019 at 10:56:30AM +0800, Like Xu wrote:
> On 2019/3/29 17:27, Alex Bennée wrote:
[...]
> > > @@ -1713,6 +1717,9 @@ static void cortex_a9_initfn(Object *obj)
> > >   #ifndef CONFIG_USER_ONLY
> > >   static uint64_t a15_l2ctlr_read(CPUARMState *env, const ARMCPRegInfo 
> > > *ri)
> > >   {
> > > +    MachineState *ms = MACHINE(qdev_get_machine());
> > 
> > How expensive is qdev_get_machine? This could potentially be a
> > performance issue if this register is read a lot.
> 
> It may not bother us cause the MachineState object would be feteched from
> qemu QOM at its first requested time and save it as static variable for
> incoming requests.

We already have a current_machine variable declared in
include/hw/boards.h.  We normally avoid using it and use
MACHINE(qdev_get_machine()) instead, but I never understood why.

-- 
Eduardo