[PATCH 21/37] KVM: arm64: Don't save the host ELR_EL2 and SPSR_EL2 on VHE systems

[Andrew Jones]

On Thu, Oct 12, 2017 at 12:41:25PM +0200, Christoffer Dall wrote:
> On non-VHE systems we need to save the ELR_EL2 and SPSR_EL2 so that we
> can return to the host in EL1 in the same state and location where we
> issued a hypercall to EL2, but these registers don't contain anything
> important on VHE, because all of the host runs in EL2.  Therefore,
> exclude them when saving/restoring the host state.

This commit message implies we start excluding now, but this patch
actually has no functional change. It just prepares things for
patch 27/37 "KVM: arm64: Defer saving/restoring system registers to
vcpu load/put on VHE". Can you please clarify it?

Thanks,
drew

> 
> Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
> ---
>  arch/arm64/kvm/hyp/sysreg-sr.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c
> index f5c1b44..354ca02 100644
> --- a/arch/arm64/kvm/hyp/sysreg-sr.c
> +++ b/arch/arm64/kvm/hyp/sysreg-sr.c
> @@ -66,6 +66,10 @@ static void __hyp_text __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>  	ctxt->gp_regs.sp_el1		= read_sysreg(sp_el1);
>  	ctxt->gp_regs.elr_el1		= read_sysreg_el1(elr);
>  	ctxt->gp_regs.spsr[KVM_SPSR_EL1]= read_sysreg_el1(spsr);
> +}
> +
> +static void __hyp_text __sysreg_save_el2_return_state(struct kvm_cpu_context *ctxt)
> +{
>  	ctxt->gp_regs.regs.pc		= read_sysreg_el2(elr);
>  	ctxt->gp_regs.regs.pstate	= read_sysreg_el2(spsr);
>  }
> @@ -75,6 +79,7 @@ void __hyp_text __sysreg_save_state_nvhe(struct kvm_cpu_context *ctxt)
>  	__sysreg_save_el1_state(ctxt);
>  	__sysreg_save_common_state(ctxt);
>  	__sysreg_save_user_state(ctxt);
> +	__sysreg_save_el2_return_state(ctxt);
>  }
>  
>  void sysreg_save_host_state_vhe(struct kvm_cpu_context *ctxt)
> @@ -88,6 +93,7 @@ void sysreg_save_guest_state_vhe(struct kvm_cpu_context *ctxt)
>  	__sysreg_save_el1_state(ctxt);
>  	__sysreg_save_common_state(ctxt);
>  	__sysreg_save_user_state(ctxt);
> +	__sysreg_save_el2_return_state(ctxt);
>  }
>  
>  static void __hyp_text __sysreg_restore_common_state(struct kvm_cpu_context *ctxt)
> @@ -127,6 +133,11 @@ static void __hyp_text __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
>  	write_sysreg(ctxt->gp_regs.sp_el1,		sp_el1);
>  	write_sysreg_el1(ctxt->gp_regs.elr_el1,		elr);
>  	write_sysreg_el1(ctxt->gp_regs.spsr[KVM_SPSR_EL1],spsr);
> +}
> +
> +static void __hyp_text
> +__sysreg_restore_el2_return_state(struct kvm_cpu_context *ctxt)
> +{
>  	write_sysreg_el2(ctxt->gp_regs.regs.pc,		elr);
>  	write_sysreg_el2(ctxt->gp_regs.regs.pstate,	spsr);
>  }
> @@ -136,6 +147,7 @@ void __hyp_text __sysreg_restore_state_nvhe(struct kvm_cpu_context *ctxt)
>  	__sysreg_restore_el1_state(ctxt);
>  	__sysreg_restore_common_state(ctxt);
>  	__sysreg_restore_user_state(ctxt);
> +	__sysreg_restore_el2_return_state(ctxt);
>  }
>  
>  void sysreg_restore_host_state_vhe(struct kvm_cpu_context *ctxt)
> @@ -149,6 +161,7 @@ void sysreg_restore_guest_state_vhe(struct kvm_cpu_context *ctxt)
>  	__sysreg_restore_el1_state(ctxt);
>  	__sysreg_restore_common_state(ctxt);
>  	__sysreg_restore_user_state(ctxt);
> +	__sysreg_restore_el2_return_state(ctxt);
>  }
>  
>  static void __hyp_text __fpsimd32_save_state(struct kvm_cpu_context *ctxt)
> -- 
> 2.9.0
>