[PATCH 13/37] KVM: arm64: Introduce VHE-specific kvm_vcpu_run

[Andrew Jones]

On Thu, Oct 12, 2017 at 12:41:17PM +0200, Christoffer Dall wrote:
> So far this is just a copy of the legacy non-VHE switch function, where
> we only change the existing calls to has_vhe() in both the original and
> new functions.
> 
> Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
> ---
>  arch/arm/include/asm/kvm_asm.h   |  4 +++
>  arch/arm64/include/asm/kvm_asm.h |  2 ++
>  arch/arm64/kvm/hyp/switch.c      | 57 ++++++++++++++++++++++++++++++++++++++++
>  virt/kvm/arm/arm.c               |  5 +++-
>  4 files changed, 67 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/include/asm/kvm_asm.h b/arch/arm/include/asm/kvm_asm.h
> index 36dd296..1a7bc5f 100644
> --- a/arch/arm/include/asm/kvm_asm.h
> +++ b/arch/arm/include/asm/kvm_asm.h
> @@ -70,8 +70,12 @@ extern void __kvm_tlb_flush_local_vmid(struct kvm_vcpu *vcpu);
>  
>  extern void __kvm_timer_set_cntvoff(u32 cntvoff_low, u32 cntvoff_high);
>  
> +/* no VHE on 32-bit :( */
> +static inline int kvm_vcpu_run(struct kvm_vcpu *vcpu) { return 0; }
> +
>  extern int __kvm_vcpu_run(struct kvm_vcpu *vcpu);
>  
> +

stray new blank line

>  extern void __init_stage2_translation(void);
>  
>  extern u64 __vgic_v3_get_ich_vtr_el2(void);
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index 7e48a39..2eb5b23 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -57,6 +57,8 @@ extern void __kvm_tlb_flush_local_vmid(struct kvm_vcpu *vcpu);
>  
>  extern void __kvm_timer_set_cntvoff(u32 cntvoff_low, u32 cntvoff_high);
>  
> +extern int kvm_vcpu_run(struct kvm_vcpu *vcpu);
> +
>  extern int __kvm_vcpu_run(struct kvm_vcpu *vcpu);
>  
>  extern u64 __vgic_v3_get_ich_vtr_el2(void);
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index ed30af5..8a0f38f 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -319,6 +319,63 @@ static bool __hyp_text fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
>  	return false;
>  }
>  
> +/* Switch to the guest for VHE systems running in EL2 */
> +int kvm_vcpu_run(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_cpu_context *host_ctxt;
> +	struct kvm_cpu_context *guest_ctxt;
> +	u64 exit_code;
> +
> +	vcpu = kern_hyp_va(vcpu);
> +
> +	host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
> +	host_ctxt->__hyp_running_vcpu = vcpu;
> +	guest_ctxt = &vcpu->arch.ctxt;
> +
> +	__sysreg_save_host_state(host_ctxt);
> +
> +	__activate_traps(vcpu);
> +	__activate_vm(vcpu);
> +
> +	__vgic_restore_state(vcpu);
> +	__timer_enable_traps(vcpu);
> +
> +	/*
> +	 * We must restore the 32-bit state before the sysregs, thanks
> +	 * to erratum #852523 (Cortex-A57) or #853709 (Cortex-A72).
> +	 */
> +	__sysreg32_restore_state(vcpu);
> +	__sysreg_restore_guest_state(guest_ctxt);
> +	__debug_switch_to_guest(vcpu);
> +
> +	/* Jump in the fire! */
> +again:
> +	exit_code = __guest_enter(vcpu, host_ctxt);
> +	/* And we're baaack! */
> +
> +	if (fixup_guest_exit(vcpu, &exit_code))
> +		goto again;
> +
> +	__sysreg_save_guest_state(guest_ctxt);
> +	__sysreg32_save_state(vcpu);
> +	__timer_disable_traps(vcpu);
> +	__vgic_save_state(vcpu);
> +
> +	__deactivate_traps(vcpu);
> +	__deactivate_vm(vcpu);
> +
> +	__sysreg_restore_host_state(host_ctxt);
> +
> +	/*
> +	 * This must come after restoring the host sysregs, since a non-VHE
> +	 * system may enable SPE here and make use of the TTBRs.
> +	 */
> +	__debug_switch_to_host(vcpu);
> +
> +	return exit_code;
> +}
> +
> +/* Switch to the guest for legacy non-VHE systems */
>  int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
>  {
>  	struct kvm_cpu_context *host_ctxt;
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index cf121b2..b11647a 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -706,7 +706,10 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  		trace_kvm_entry(*vcpu_pc(vcpu));
>  		guest_enter_irqoff();
>  
> -		ret = kvm_call_hyp(__kvm_vcpu_run, vcpu);
> +		if (has_vhe())
> +			ret = kvm_vcpu_run(vcpu);
> +		else
> +			ret = kvm_call_hyp(__kvm_vcpu_run, vcpu);

So kvm_vcpu_run() is going to be VHE only, but the only way for people
stepping through the code to know that is by seeing this callsite or by
reading the comment above it. Everywhere else we make it much more clear
with the _vhe and _nvhe suffixes. I wonder if we should keep that pattern
by adding

 static int kvm_vcpu_run(struct kvm_vcpu *vcpu)
 {
    if (has_vhe())
        ret = kvm_vcpu_run_vhe(vcpu);
    else
        ret = kvm_call_hyp(__kvm_vcpu_run_nvhe, vcpu);
 }

to virt/kvm/arm/arm.c and then calling that from here.

I'm afraid the __ prefix is too ambiguous in the kernel to interpret
__foo() as the hyp mode non-VHE version of foo(), the hyp mode VHE
version.

Thanks,
drew

>  
>  		vcpu->mode = OUTSIDE_GUEST_MODE;
>  		vcpu->stat.exits++;
> -- 
> 2.9.0
>