[PATCH 07/37] KVM: arm/arm64: Add kvm_vcpu_load_sysregs and kvm_vcpu_put_sysregs

[Andrew Jones]

On Thu, Oct 12, 2017 at 12:41:11PM +0200, Christoffer Dall wrote:
> As we are about to move a buch of save/restore logic for VHE kernels to
> the load and put functions, we need some infrastructure to do this.
> 
> Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
> ---
>  arch/arm/include/asm/kvm_host.h   |  3 +++
>  arch/arm64/include/asm/kvm_host.h |  3 +++
>  arch/arm64/kvm/hyp/sysreg-sr.c    | 27 +++++++++++++++++++++++++++
>  virt/kvm/arm/arm.c                |  2 ++
>  4 files changed, 35 insertions(+)
> 
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index 1100170..13f8165 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -290,4 +290,7 @@ int kvm_arm_vcpu_arch_get_attr(struct kvm_vcpu *vcpu,
>  int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
>  			       struct kvm_device_attr *attr);
>  
> +static inline void kvm_vcpu_load_sysregs(struct kvm_vcpu *vcpu) {}
> +static inline void kvm_vcpu_put_sysregs(struct kvm_vcpu *vcpu) {}
> +
>  #endif /* __ARM_KVM_HOST_H__ */
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 27305e7..7d3bfa7 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -383,4 +383,7 @@ static inline void __cpu_init_stage2(void)
>  		  "PARange is %d bits, unsupported configuration!", parange);
>  }
>  
> +void kvm_vcpu_load_sysregs(struct kvm_vcpu *vcpu);
> +void kvm_vcpu_put_sysregs(struct kvm_vcpu *vcpu);
> +
>  #endif /* __ARM64_KVM_HOST_H__ */
> diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c
> index c54cc2a..b7438c8 100644
> --- a/arch/arm64/kvm/hyp/sysreg-sr.c
> +++ b/arch/arm64/kvm/hyp/sysreg-sr.c
> @@ -183,3 +183,30 @@ void __hyp_text __sysreg32_restore_state(struct kvm_vcpu *vcpu)
>  	if (vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY)
>  		write_sysreg(sysreg[DBGVCR32_EL2], dbgvcr32_el2);
>  }
> +
> +/**
> + * kvm_vcpu_load_sysregs - Load guest system register to physical CPU
> + *
> + * @vcpu: The VCPU pointer
> + *
> + * If the kernel runs in EL2 then load the system register state for the VCPU
> + * for EL1 onto the physical CPU so that we can go back and foward between the
> + * VM and the hypervisor without switching all this state around.

Actually, on second thought, I'm a bit confused by this comment. Maybe
it'll be clearer after the code that goes here will be added, but, ATM,
I'm not sure why we want to specifically load EL1 VCPU state here. Will
that always be the case, even with nested? Also, I'm not sure what
alternative loading scheme we're avoiding in order to ensure the state
isn't "switched around", which I don't really understand either.

Thanks,
drew