Re: [PATCH 1/3] KVM: arm64: Implement vGICv3 distributor and redistributor access from userspace

[Christoffer Dall <christoffer.dall@linaro.org>]

On Mon, Aug 31, 2015 at 10:35:05AM +0300, Pavel Fedin wrote:
>  Hello!
> 
> > > +	len = vgic_v3_get_reg_size(attr);
> > > +	if (len < 0)
> > > +		return len;
> > >
> > > -	return -ENXIO;
> > > +	ret = vgic_v3_attr_regs_access(dev, attr, (len == 8) ? (void *)&reg64 :
> > > +					(void *)&reg, len, false);
> > 
> > this use of the ternary operator is terrible, but it should be solved if
> > you always use a u64 for the reg parameter.
> 
>  I also dislike this, but this is the best thing i could invent. This is dictated by put_user() and
> get_user(), which rely on typeof() of their arguments. Well, i could do some castings, but they are
> no less ugly, and would give more headache to bigendian systems.
> However, what about doing the same thing as GET/SET_ONE_REG does by just assuming that everything is
> 64-bit wide? This would automatically resolve two other issues you have commented on. By the way,
> handling it in userspace would also be simpler.
> 
Sounds fine to me, definitely if you must do a cast doing it in a
function between typed variables is strictly preferred to passing void *
values between functions.

-Christoffer