Re: [PATCH v3 26/27] KVM: arm64: Log an error if trapping a read-from-write-only GICv3 access

[Christoffer Dall <cdall@linaro.org>]

On Fri, Jun 09, 2017 at 12:49:55PM +0100, Marc Zyngier wrote:
> A read-from-write-only GICv3 access should UNDEF at EL1. But since
> we're in complete paranoia-land with broken CPUs, let's assume the
> worse and gracefully handle the case.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Reviewed-by: Christoffer Dall <cdall@linaro.org>

> ---
>  arch/arm64/kvm/sys_regs.c     | 12 ++++++++----
>  virt/kvm/arm/hyp/vgic-v3-sr.c |  4 ++++
>  2 files changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 0fe27024a2e1..8d51c075966d 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -56,7 +56,8 @@
>   */
>  
>  static bool read_from_write_only(struct kvm_vcpu *vcpu,
> -				 const struct sys_reg_params *params)
> +				 struct sys_reg_params *params,
> +				 const struct sys_reg_desc *r)
>  {
>  	WARN_ONCE(1, "Unexpected sys_reg read to write-only register\n");
>  	print_sys_reg_instr(params);
> @@ -93,7 +94,7 @@ static bool access_dcsw(struct kvm_vcpu *vcpu,
>  			const struct sys_reg_desc *r)
>  {
>  	if (!p->is_write)
> -		return read_from_write_only(vcpu, p);
> +		return read_from_write_only(vcpu, p, r);
>  
>  	kvm_set_way_flush(vcpu);
>  	return true;
> @@ -135,7 +136,7 @@ static bool access_gic_sgi(struct kvm_vcpu *vcpu,
>  			   const struct sys_reg_desc *r)
>  {
>  	if (!p->is_write)
> -		return read_from_write_only(vcpu, p);
> +		return read_from_write_only(vcpu, p, r);
>  
>  	vgic_v3_dispatch_sgi(vcpu, p->regval);
>  
> @@ -773,7 +774,7 @@ static bool access_pmswinc(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
>  		return trap_raz_wi(vcpu, p, r);
>  
>  	if (!p->is_write)
> -		return read_from_write_only(vcpu, p);
> +		return read_from_write_only(vcpu, p, r);
>  
>  	if (pmu_write_swinc_el0_disabled(vcpu))
>  		return false;
> @@ -953,7 +954,10 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  
>  	{ SYS_DESC(SYS_VBAR_EL1), NULL, reset_val, VBAR_EL1, 0 },
>  
> +	{ SYS_DESC(SYS_ICC_EOIR0_EL1), read_from_write_only },
> +	{ SYS_DESC(SYS_ICC_DIR_EL1), read_from_write_only },
>  	{ SYS_DESC(SYS_ICC_SGI1R_EL1), access_gic_sgi },
> +	{ SYS_DESC(SYS_ICC_EOIR1_EL1), read_from_write_only },
>  	{ SYS_DESC(SYS_ICC_SRE_EL1), access_gic_sre },
>  
>  	{ SYS_DESC(SYS_CONTEXTIDR_EL1), access_vm_reg, reset_val, CONTEXTIDR_EL1, 0 },
> diff --git a/virt/kvm/arm/hyp/vgic-v3-sr.c b/virt/kvm/arm/hyp/vgic-v3-sr.c
> index 15b557697086..b26ce58b012a 100644
> --- a/virt/kvm/arm/hyp/vgic-v3-sr.c
> +++ b/virt/kvm/arm/hyp/vgic-v3-sr.c
> @@ -980,6 +980,8 @@ int __hyp_text __vgic_v3_perform_cpuif_access(struct kvm_vcpu *vcpu)
>  		break;
>  	case SYS_ICC_EOIR0_EL1:
>  	case SYS_ICC_EOIR1_EL1:
> +		if (unlikely(is_read))
> +			return 0;
>  		fn = __vgic_v3_write_eoir;
>  		break;
>  	case SYS_ICC_GRPEN1_EL1:
> @@ -1039,6 +1041,8 @@ int __hyp_text __vgic_v3_perform_cpuif_access(struct kvm_vcpu *vcpu)
>  			fn = __vgic_v3_write_bpr0;
>  		break;
>  	case SYS_ICC_DIR_EL1:
> +		if (unlikely(is_read))
> +			return 0;
>  		fn = __vgic_v3_write_dir;
>  		break;
>  	case SYS_ICC_RPR_EL1:
> -- 
> 2.11.0
>