Re: [PATCH v5 01/22] KVM: arm64: Introduce template for inline functions

[Gavin Shan]

Hi Oliver,

On 3/23/22 3:42 AM, Oliver Upton wrote:
> On Tue, Mar 22, 2022 at 04:06:49PM +0800, Gavin Shan wrote:
> > The inline functions used to get the SMCCC parameters have same
> > layout. It means these functions can be presented by an unified
> > template, to make the code simplified. Besides, this adds more
> > similar inline functions like smccc_get_arg{4,5,6,7,8}() to get
> > more SMCCC arguments, which are needed by SDEI virtualization
> > support.
> >
> > Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
> > ---
> >   include/kvm/arm_hypercalls.h | 24 ++++++++++++------------
> >   1 file changed, 12 insertions(+), 12 deletions(-)
> >
> > diff --git a/include/kvm/arm_hypercalls.h b/include/kvm/arm_hypercalls.h
> > index 0e2509d27910..d5144c852fe4 100644
> > --- a/include/kvm/arm_hypercalls.h
> > +++ b/include/kvm/arm_hypercalls.h
> > @@ -13,20 +13,20 @@ static inline u32 smccc_get_function(struct kvm_vcpu *vcpu)
> >   	return vcpu_get_reg(vcpu, 0);
> >   }
> >   
> > -static inline unsigned long smccc_get_arg1(struct kvm_vcpu *vcpu)
> > -{
> > -	return vcpu_get_reg(vcpu, 1);
> > -}
> > -
> > -static inline unsigned long smccc_get_arg2(struct kvm_vcpu *vcpu)
> > -{
> > -	return vcpu_get_reg(vcpu, 2);
> > +#define SMCCC_DECLARE_GET_ARG(reg)					\
> > +static inline unsigned long smccc_get_arg##reg(struct kvm_vcpu *vcpu)	\
> > +{									\
> > +	return vcpu_get_reg(vcpu, reg);					\
> >   }
> >   
> > -static inline unsigned long smccc_get_arg3(struct kvm_vcpu *vcpu)
> > -{
> > -	return vcpu_get_reg(vcpu, 3);
> > -}
> > +SMCCC_DECLARE_GET_ARG(1)
> > +SMCCC_DECLARE_GET_ARG(2)
> > +SMCCC_DECLARE_GET_ARG(3)
> > +SMCCC_DECLARE_GET_ARG(4)
> > +SMCCC_DECLARE_GET_ARG(5)
> > +SMCCC_DECLARE_GET_ARG(6)
> > +SMCCC_DECLARE_GET_ARG(7)
> > +SMCCC_DECLARE_GET_ARG(8)
>
> Hmm. What if we specify a single inline function where the caller passes
> the arg # as a parameter? We really just want to abstract away the
> off-by-one difference between GP registers and SMCCC arguments.
>
> Macros generally make me uneasy for template functions, but I may be in
> the vocal minority on this topic :)

I think it's a good idea to have smccc_get_arg(unsigned char index).
However, it will cause more code changes because the following functions
have been used. Anyway, I think it's still worthy to pass @index to
differentiate the argument index. I will change it accordingly in
next respin.

   smccc_get_arg1()
   smccc_get_arg2()
   smccc_get_arg3()

Thanks,
Gavin