Subject: [PATCH 13/18] KVM: ARM64: Add reset and access handlers for PMOVSSET_EL0 and PMOVSCLR_EL0 register

From: [email-masked] (Christoffer Dall)
Date: Fri, 17 Jul 2015 17:02:50 +0200

On Mon, Jul 06, 2015 at 10:17:43AM +0800, shannon.zhao at linaro.org wrote:
> From: Shannon Zhao <[email-masked]>
> 
> Since the reset value of PMOVSSET_EL0 and PMOVSCLR_EL0 is UNKNOWN, use
> reset_unknown for its reset handler. Add access handler which emulates
> writing and reading PMOVSSET_EL0 or PMOVSCLR_EL0 register.
> 
> Signed-off-by: Shannon Zhao <[email-masked]>
> ---
>  arch/arm64/kvm/sys_regs.c | 30 ++++++++++++++++++++++++++++--
>  1 file changed, 28 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index cbc07b8..ec80937 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -496,6 +496,32 @@ static bool access_pmintenclr(struct kvm_vcpu *vcpu,
>  	return true;
>  }
>  
> +/* PMOVSSET_EL0 accessor. */
> +static bool access_pmovsset(struct kvm_vcpu *vcpu,
> +			    const struct sys_reg_params *p,
> +			    const struct sys_reg_desc *r)
> +{
> +	if (p->is_write)
> +		vcpu->arch.pmu.overflow_status |= *vcpu_reg(vcpu, p->Rt);
> +	else
> +		*vcpu_reg(vcpu, p->Rt) = vcpu->arch.pmu.overflow_status;

if you store this state in PMOVSSET_EL0 you get VM migration
save/restore support for (almost) free.

-Christoffer

> +
> +	return true;
> +}
> +
> +/* PMOVSCLR_EL0 accessor. */
> +static bool access_pmovsclr(struct kvm_vcpu *vcpu,
> +			    const struct sys_reg_params *p,
> +			    const struct sys_reg_desc *r)
> +{
> +	if (p->is_write)
> +		vcpu->arch.pmu.overflow_status &= (~*vcpu_reg(vcpu, p->Rt));
> +	else
> +		*vcpu_reg(vcpu, p->Rt) = vcpu->arch.pmu.overflow_status;
> +
> +	return true;
> +}
> +
>  /* Silly macro to expand the DBG{BCR,BVR,WVR,WCR}n_EL1 registers in one go */
>  #define DBG_BCR_BVR_WCR_WVR_EL1(n)					\
>  	/* DBGBVRn_EL1 */						\
> @@ -696,7 +722,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  	  access_pmcntenclr, reset_unknown, PMCNTENCLR_EL0 },
>  	/* PMOVSCLR_EL0 */
>  	{ Op0(0b11), Op1(0b011), CRn(0b1001), CRm(0b1100), Op2(0b011),
> -	  trap_raz_wi },
> +	  access_pmovsclr, reset_unknown, PMOVSCLR_EL0 },
>  	/* PMSWINC_EL0 */
>  	{ Op0(0b11), Op1(0b011), CRn(0b1001), CRm(0b1100), Op2(0b100),
>  	  trap_raz_wi },
> @@ -723,7 +749,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  	  trap_raz_wi },
>  	/* PMOVSSET_EL0 */
>  	{ Op0(0b11), Op1(0b011), CRn(0b1001), CRm(0b1110), Op2(0b011),
> -	  trap_raz_wi },
> +	  access_pmovsset, reset_unknown, PMOVSSET_EL0 },
>  
>  	/* TPIDR_EL0 */
>  	{ Op0(0b11), Op1(0b011), CRn(0b1101), CRm(0b0000), Op2(0b010),
> -- 
> 2.1.0
>