Re: [PATCH v8 08/20] KVM: ARM64: Add access handler for event typer register

[Marc Zyngier <marc.zyngier@arm.com>]

On Thu, 7 Jan 2016 20:36:45 +0800
Shannon Zhao <zhaoshenglong@huawei.com> wrote:

> 
> 
> On 2016/1/7 19:03, Marc Zyngier wrote:
> > On 22/12/15 08:08, Shannon Zhao wrote:
> >> > From: Shannon Zhao <shannon.zhao@linaro.org>
> >> > 
> >> > These kind of registers include PMEVTYPERn, PMCCFILTR and PMXEVTYPER
> >> > which is mapped to PMEVTYPERn or PMCCFILTR.
> >> > 
> >> > The access handler translates all aarch32 register offsets to aarch64
> >> > ones and uses vcpu_sys_reg() to access their values to avoid taking care
> >> > of big endian.
> >> > 
> >> > When writing to these registers, create a perf_event for the selected
> >> > event type.
> >> > 
> >> > Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
> >> > ---
> >> >  arch/arm64/kvm/sys_regs.c | 156 +++++++++++++++++++++++++++++++++++++++++++++-
> >> >  1 file changed, 154 insertions(+), 2 deletions(-)
> >> > 
> >> > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> >> > index 2552db1..ed2939b 100644
> >> > --- a/arch/arm64/kvm/sys_regs.c
> >> > +++ b/arch/arm64/kvm/sys_regs.c
> >> > @@ -505,6 +505,70 @@ static bool access_pmceid(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
> >> >  	return true;
> >> >  }
> >> >  
> >> > +static inline bool pmu_counter_idx_valid(struct kvm_vcpu *vcpu, u64 idx)
> >> > +{
> >> > +	u64 pmcr, val;
> >> > +
> >> > +	pmcr = vcpu_sys_reg(vcpu, PMCR_EL0);
> >> > +	val = (pmcr >> ARMV8_PMCR_N_SHIFT) & ARMV8_PMCR_N_MASK;
> >> > +	if (idx >= val && idx != ARMV8_CYCLE_IDX)
> >> > +		return false;
> >> > +
> >> > +	return true;
> >> > +}
> >> > +
> >> > +static bool access_pmu_evtyper(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
> >> > +			       const struct sys_reg_desc *r)
> >> > +{
> >> > +	u64 idx, reg;
> >> > +
> >> > +	if (r->CRn == 9) {
> >> > +		/* PMXEVTYPER_EL0 */
> >> > +		reg = 0;
> > Is there any particular reason why you're not setting reg to PMSELR_EL0,
> > since this is what you're using?
> > 
> >> > +	} else {
> >> > +		if (!p->is_aarch32) {
> >> > +			/* PMEVTYPERn_EL0 or PMCCFILTR_EL0 */
> >> > +			reg = r->reg;
> >> > +		} else {
> >> > +			if (r->CRn == 14 && r->CRm == 15 && r->Op2 == 7) {
> >> > +				reg = PMCCFILTR_EL0;
> >> > +			} else {
> >> > +				reg = ((r->CRm & 3) << 3) | (r->Op2 & 7);
> >> > +				reg += PMEVTYPER0_EL0;
> >> > +			}
> >> > +		}
> >> > +	}
> >> > +
> >> > +	switch (reg) {
> >> > +	case PMEVTYPER0_EL0 ... PMEVTYPER30_EL0:
> >> > +		idx = reg - PMEVTYPER0_EL0;
> >> > +		if (!pmu_counter_idx_valid(vcpu, idx))
> >> > +			return true;
> >> > +		break;
> >> > +	case PMCCFILTR_EL0:
> >> > +		idx = ARMV8_CYCLE_IDX;
> >> > +		break;
> >> > +	default:
> > This would allow this case to be more precise, and we could have the
> > default case as a bug handler.
> > 
> 
> It turns out that I refactor this function like below:
> 
> +static bool access_pmu_evtyper(struct kvm_vcpu *vcpu, struct
> sys_reg_params *p,
> +                              const struct sys_reg_desc *r)
> +{
> +       u64 idx, reg = 0;
> +
> +       if (r->CRn == 9) {
> +               /* PMXEVTYPER_EL0 */
> +               idx = vcpu_sys_reg(vcpu, PMSELR_EL0) & ARMV8_COUNTER_MASK;
> +               reg = PMEVTYPER0_EL0 + idx;
> +       } else {
> +               if (r->CRm == 15 && r->Op2 == 7) {
> +                       idx = ARMV8_CYCLE_IDX;
> +                       reg = PMCCFILTR_EL0;
> +               } else {
> +                       /* PMEVTYPERn_EL0 */
> +                       idx = ((r->CRm & 3) << 3) | (r->Op2 & 7);
> +                       reg = PMEVTYPER0_EL0 + idx;
> +               }
> +       }
> +
> +       BUG_ON(reg == 0);
> +
> +       if (!pmu_counter_idx_valid(vcpu, idx))
> +               return false;
> +
> +       if (p->is_write) {
> +               kvm_pmu_set_counter_event_type(vcpu, p->regval, idx);
> +               vcpu_sys_reg(vcpu, reg) = p->regval & ARMV8_EVTYPE_MASK;
> +       } else {
> +               p->regval = vcpu_sys_reg(vcpu, reg) & ARMV8_EVTYPE_MASK;
> +       }
> +
> +       return true;
> +}
> 
> How about this?

Yup, looks good to me.

	M.
-- 
Jazz is not dead. It just smells funny.