Re: [PATCH v2 07/22] KVM: ARM64: Add reset and access handlers for PMCEID0 and PMCEID1 register

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

On 11/09/15 09:55, Shannon Zhao wrote:
> From: Shannon Zhao <shannon.zhao@linaro.org>
> 
> Add reset handler which gets host value of PMCEID0 or PMCEID1. Since
> write action to PMCEID0 or PMCEID1 is ignored, add a new case for this.
> 
> Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
> ---
>  arch/arm64/kvm/sys_regs.c | 36 ++++++++++++++++++++++++++++++++----
>  1 file changed, 32 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 24b8972..b3bc717 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -251,6 +251,26 @@ static void reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
>  					  | (ARMV8_PMCR_MASK & 0xdecafbad);
>  }
>  
> +static void reset_pmceid(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
> +{
> +	u32 pmceid;
> +
> +	if (r->reg == PMCEID0_EL0 || r->reg == c9_PMCEID0) {
> +		asm volatile("mrs %0, pmceid0_el0\n" : "=r" (pmceid));

Careful here. mrs always acts on a 64bit quantity, even if the register is
internally 32bit. I'd rather you use a u64 variable.

> +		if (!vcpu_mode_is_32bit(vcpu))
> +			vcpu_sys_reg(vcpu, r->reg) = pmceid;
> +		else
> +			vcpu_cp15(vcpu, r->reg) = pmceid;
> +	} else {
> +		/* PMCEID1_EL0 or c9_PMCEID1 */
> +		asm volatile("mrs %0, pmceid1_el0\n" : "=r" (pmceid));
> +		if (!vcpu_mode_is_32bit(vcpu))
> +			vcpu_sys_reg(vcpu, r->reg) = pmceid;
> +		else
> +			vcpu_cp15(vcpu, r->reg) = pmceid;

Maybe we could have a helper for this kind of sequence:

static void vcpu_sysreg_write(vcpu, const struct sys_reg_desc *r, u64 val)
{
	if (!vcpu_mode_is_32_bit(vcpu))
		vcpu_sys_reg(vcpu, r->reg) = val;
	else
		vcpu_cp15(vcpu, r->reg) = lower_32_bit(val);
}

> +	}
> +}
> +
>  /* PMU registers accessor. */
>  static bool access_pmu_regs(struct kvm_vcpu *vcpu,
>  			    const struct sys_reg_params *p,
> @@ -268,6 +288,9 @@ static bool access_pmu_regs(struct kvm_vcpu *vcpu,
>  			vcpu_sys_reg(vcpu, r->reg) = val;
>  			break;
>  		}
> +		case PMCEID0_EL0:
> +		case PMCEID1_EL0:
> +			return ignore_write(vcpu, p);
>  		default:
>  			vcpu_sys_reg(vcpu, r->reg) = *vcpu_reg(vcpu, p->Rt);
>  			break;
> @@ -488,10 +511,10 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  	  access_pmu_regs, reset_unknown, PMSELR_EL0 },
>  	/* PMCEID0_EL0 */
>  	{ Op0(0b11), Op1(0b011), CRn(0b1001), CRm(0b1100), Op2(0b110),
> -	  trap_raz_wi },
> +	  access_pmu_regs, reset_pmceid, PMCEID0_EL0 },
>  	/* PMCEID1_EL0 */
>  	{ Op0(0b11), Op1(0b011), CRn(0b1001), CRm(0b1100), Op2(0b111),
> -	  trap_raz_wi },
> +	  access_pmu_regs, reset_pmceid, PMCEID1_EL0 },
>  	/* PMCCNTR_EL0 */
>  	{ Op0(0b11), Op1(0b011), CRn(0b1001), CRm(0b1101), Op2(0b000),
>  	  trap_raz_wi },
> @@ -692,6 +715,9 @@ static bool access_pmu_cp15_regs(struct kvm_vcpu *vcpu,
>  			vcpu_cp15(vcpu, r->reg) = val;
>  			break;
>  		}
> +		case c9_PMCEID0:
> +		case c9_PMCEID1:
> +			return ignore_write(vcpu, p);
>  		default:
>  			vcpu_cp15(vcpu, r->reg) = *vcpu_reg(vcpu, p->Rt);
>  			break;
> @@ -738,8 +764,10 @@ static const struct sys_reg_desc cp15_regs[] = {
>  	{ Op1( 0), CRn( 9), CRm(12), Op2( 3), trap_raz_wi },
>  	{ Op1( 0), CRn( 9), CRm(12), Op2( 5), access_pmu_cp15_regs,
>  	  reset_unknown_cp15, c9_PMSELR },
> -	{ Op1( 0), CRn( 9), CRm(12), Op2( 6), trap_raz_wi },
> -	{ Op1( 0), CRn( 9), CRm(12), Op2( 7), trap_raz_wi },
> +	{ Op1( 0), CRn( 9), CRm(12), Op2( 6), access_pmu_cp15_regs,
> +	  reset_pmceid, c9_PMCEID0 },
> +	{ Op1( 0), CRn( 9), CRm(12), Op2( 7), access_pmu_cp15_regs,
> +	  reset_pmceid, c9_PMCEID1 },
>  	{ Op1( 0), CRn( 9), CRm(13), Op2( 0), trap_raz_wi },
>  	{ Op1( 0), CRn( 9), CRm(13), Op2( 1), trap_raz_wi },
>  	{ Op1( 0), CRn( 9), CRm(13), Op2( 2), trap_raz_wi },
> 


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