Subject: [RFC PATCH v2 37/38] KVM: arm64: Respect the virtual HCR_EL2.NV1 bit setting

From: [email-masked] (Christoffer Dall)
Date: Mon, 31 Jul 2017 14:53:00 +0200

On Tue, Jul 18, 2017 at 11:59:03AM -0500, Jintack Lim wrote:
> Forward ELR_EL1, SPSR_EL1 and VBAR_EL1 traps to the virtual EL2 if the
> virtual HCR_EL2.NV bit is set.
> 
> This is for recursive nested virtualization.
> 
> Signed-off-by: Jintack Lim <[email-masked]>
> ---
>  arch/arm64/include/asm/kvm_arm.h |  1 +
>  arch/arm64/kvm/sys_regs.c        | 18 ++++++++++++++++++
>  2 files changed, 19 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index aeaac4e..a1274b7 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -23,6 +23,7 @@
>  #include <asm/types.h>
>  
>  /* Hyp Configuration Register (HCR) bits */
> +#define HCR_NV1		(UL(1) << 43)
>  #define HCR_NV		(UL(1) << 42)
>  #define HCR_E2H		(UL(1) << 34)
>  #define HCR_ID		(UL(1) << 33)
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 3e4ec5e..6f67666 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1031,6 +1031,15 @@ static bool trap_el2_regs(struct kvm_vcpu *vcpu,
>  	return true;
>  }
>  
> +/* This function is to support the recursive nested virtualization */
> +static bool forward_nv1_traps(struct kvm_vcpu *vcpu, struct sys_reg_params *p)
> +{
> +	if (!vcpu_mode_el2(vcpu) && (vcpu_sys_reg(vcpu, HCR_EL2) & HCR_NV1))
> +		return true;
> +
> +	return false;
> +}
> +
>  static bool access_elr(struct kvm_vcpu *vcpu,
>  		struct sys_reg_params *p,
>  		const struct sys_reg_desc *r)
> @@ -1038,6 +1047,9 @@ static bool access_elr(struct kvm_vcpu *vcpu,
>  	if (el12_reg(p) && forward_nv_traps(vcpu))
>  		return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
>  
> +	if (!el12_reg(p) && forward_nv1_traps(vcpu, p))
> +		return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
> +
>  	access_rw(p, &vcpu->arch.ctxt.gp_regs.elr_el1);
>  	return true;
>  }
> @@ -1049,6 +1061,9 @@ static bool access_spsr(struct kvm_vcpu *vcpu,
>  	if (el12_reg(p) && forward_nv_traps(vcpu))
>  		return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
>  
> +	if (!el12_reg(p) && forward_nv1_traps(vcpu, p))
> +		return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
> +
>  	access_rw(p, &vcpu->arch.ctxt.gp_regs.spsr[KVM_SPSR_EL1]);
>  	return true;
>  }
> @@ -1060,6 +1075,9 @@ static bool access_vbar(struct kvm_vcpu *vcpu,
>  	if (el12_reg(p) && forward_nv_traps(vcpu))
>  		return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
>  
> +	if (!el12_reg(p) && forward_nv1_traps(vcpu, p))
> +		return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
> +
>  	access_rw(p, &vcpu_sys_reg(vcpu, r->reg));
>  	return true;
>  }
> -- 
> 1.9.1
> 

Will we ever trap on any of these if !el12_reg() && !forward_nv_traps()

?

If not, do we need the !el12_reg() checks here?

Thanks,
-Christoffer