Re: [PATCH v2 2/8] KVM: arm64: Make vcpu_{read,write}_sys_reg available to HYP code

[Vincent Donnefort]

On Fri, Jun 19, 2026 at 08:07:13AM +0100, Fuad Tabba wrote:
> The vcpu_{read,write}_sys_reg() accessors are host-only, so helpers
> built on them such as kvm_vcpu_set_be()/kvm_vcpu_is_be() cannot be
> shared with hyp code. exception.c already wraps them in
> __vcpu_{read,write}_sys_reg(), which pick the host- or hyp-side accessor
> via has_vhe() and so are valid in any context.
> 
> Move those wrappers to kvm_emulate.h as kvm_vcpu_{read,write}_sys_reg()
> and switch the callers over, so a follow-up series can share that
> emulation code at EL2.
> 
> No functional change intended.
> 
> Signed-off-by: Fuad Tabba <tabba@xxxxxxxxxx>

Reviewed-by: Vincent Donnefort <vdonnefort@xxxxxxxxxx>

> ---
>  arch/arm64/include/asm/kvm_emulate.h | 22 +++++++++++++++---
>  arch/arm64/kvm/hyp/exception.c       | 34 ++++++++--------------------
>  2 files changed, 28 insertions(+), 28 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index 5bf3d7e1d92c..80b30fead3d1 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -506,6 +506,22 @@ static inline unsigned long kvm_vcpu_get_mpidr_aff(struct kvm_vcpu *vcpu)
>  	return __vcpu_sys_reg(vcpu, MPIDR_EL1) & MPIDR_HWID_BITMASK;
>  }
>  
> +static inline u64 kvm_vcpu_read_sys_reg(const struct kvm_vcpu *vcpu, int reg)
> +{
> +	if (has_vhe())
> +		return vcpu_read_sys_reg(vcpu, reg);
> +
> +	return __vcpu_sys_reg(vcpu, reg);
> +}
> +
> +static inline void kvm_vcpu_write_sys_reg(struct kvm_vcpu *vcpu, u64 val, int reg)
> +{
> +	if (has_vhe())
> +		vcpu_write_sys_reg(vcpu, val, reg);
> +	else
> +		__vcpu_assign_sys_reg(vcpu, reg, val);
> +}
> +
>  static inline void kvm_vcpu_set_be(struct kvm_vcpu *vcpu)
>  {
>  	if (vcpu_mode_is_32bit(vcpu)) {
> @@ -516,9 +532,9 @@ static inline void kvm_vcpu_set_be(struct kvm_vcpu *vcpu)
>  
>  		r = vcpu_has_nv(vcpu) ? SCTLR_EL2 : SCTLR_EL1;
>  
> -		sctlr = vcpu_read_sys_reg(vcpu, r);
> +		sctlr = kvm_vcpu_read_sys_reg(vcpu, r);
>  		sctlr |= SCTLR_ELx_EE;
> -		vcpu_write_sys_reg(vcpu, sctlr, r);
> +		kvm_vcpu_write_sys_reg(vcpu, sctlr, r);
>  	}
>  }
>  
> @@ -533,7 +549,7 @@ static inline bool kvm_vcpu_is_be(struct kvm_vcpu *vcpu)
>  	r = is_hyp_ctxt(vcpu) ? SCTLR_EL2 : SCTLR_EL1;
>  	bit = vcpu_mode_priv(vcpu) ? SCTLR_ELx_EE : SCTLR_EL1_E0E;
>  
> -	return vcpu_read_sys_reg(vcpu, r) & bit;
> +	return kvm_vcpu_read_sys_reg(vcpu, r) & bit;
>  }
>  
>  static inline unsigned long vcpu_data_guest_to_host(struct kvm_vcpu *vcpu,
> diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c
> index bef40ddb16db..2cb68dc7d441 100644
> --- a/arch/arm64/kvm/hyp/exception.c
> +++ b/arch/arm64/kvm/hyp/exception.c
> @@ -20,22 +20,6 @@
>  #error Hypervisor code only!
>  #endif
>  
> -static inline u64 __vcpu_read_sys_reg(const struct kvm_vcpu *vcpu, int reg)
> -{
> -	if (has_vhe())
> -		return vcpu_read_sys_reg(vcpu, reg);
> -
> -	return __vcpu_sys_reg(vcpu, reg);
> -}
> -
> -static inline void __vcpu_write_sys_reg(struct kvm_vcpu *vcpu, u64 val, int reg)
> -{
> -	if (has_vhe())
> -		vcpu_write_sys_reg(vcpu, val, reg);
> -	else
> -		__vcpu_assign_sys_reg(vcpu, reg, val);
> -}
> -
>  static void __vcpu_write_spsr(struct kvm_vcpu *vcpu, unsigned long target_mode,
>  			      u64 val)
>  {
> @@ -101,14 +85,14 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
>  
>  	switch (target_mode) {
>  	case PSR_MODE_EL1h:
> -		vbar = __vcpu_read_sys_reg(vcpu, VBAR_EL1);
> -		sctlr = __vcpu_read_sys_reg(vcpu, SCTLR_EL1);
> -		__vcpu_write_sys_reg(vcpu, *vcpu_pc(vcpu), ELR_EL1);
> +		vbar = kvm_vcpu_read_sys_reg(vcpu, VBAR_EL1);
> +		sctlr = kvm_vcpu_read_sys_reg(vcpu, SCTLR_EL1);
> +		kvm_vcpu_write_sys_reg(vcpu, *vcpu_pc(vcpu), ELR_EL1);
>  		break;
>  	case PSR_MODE_EL2h:
> -		vbar = __vcpu_read_sys_reg(vcpu, VBAR_EL2);
> -		sctlr = __vcpu_read_sys_reg(vcpu, SCTLR_EL2);
> -		__vcpu_write_sys_reg(vcpu, *vcpu_pc(vcpu), ELR_EL2);
> +		vbar = kvm_vcpu_read_sys_reg(vcpu, VBAR_EL2);
> +		sctlr = kvm_vcpu_read_sys_reg(vcpu, SCTLR_EL2);
> +		kvm_vcpu_write_sys_reg(vcpu, *vcpu_pc(vcpu), ELR_EL2);
>  		break;
>  	default:
>  		/* Don't do that */
> @@ -185,7 +169,7 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
>   */
>  static unsigned long get_except32_cpsr(struct kvm_vcpu *vcpu, u32 mode)
>  {
> -	u32 sctlr = __vcpu_read_sys_reg(vcpu, SCTLR_EL1);
> +	u32 sctlr = kvm_vcpu_read_sys_reg(vcpu, SCTLR_EL1);
>  	unsigned long old, new;
>  
>  	old = *vcpu_cpsr(vcpu);
> @@ -281,7 +265,7 @@ static void enter_exception32(struct kvm_vcpu *vcpu, u32 mode, u32 vect_offset)
>  {
>  	unsigned long spsr = *vcpu_cpsr(vcpu);
>  	bool is_thumb = (spsr & PSR_AA32_T_BIT);
> -	u32 sctlr = __vcpu_read_sys_reg(vcpu, SCTLR_EL1);
> +	u32 sctlr = kvm_vcpu_read_sys_reg(vcpu, SCTLR_EL1);
>  	u32 return_address;
>  
>  	*vcpu_cpsr(vcpu) = get_except32_cpsr(vcpu, mode);
> @@ -305,7 +289,7 @@ static void enter_exception32(struct kvm_vcpu *vcpu, u32 mode, u32 vect_offset)
>  	if (sctlr & (1 << 13))
>  		vect_offset += 0xffff0000;
>  	else /* always have security exceptions */
> -		vect_offset += __vcpu_read_sys_reg(vcpu, VBAR_EL1);
> +		vect_offset += kvm_vcpu_read_sys_reg(vcpu, VBAR_EL1);
>  
>  	*vcpu_pc(vcpu) = vect_offset;
>  }
> -- 
> 2.55.0.rc0.738.g0c8ab3ebcc-goog
>