[PATCH v3 13/41] KVM: arm64: Factor out fault info population and gic workarounds

[Julien Thierry]

On 12/01/18 12:07, Christoffer Dall wrote:
> The current world-switch function has functionality to detect a number
> of cases where we need to fixup some part of the exit condition and
> possibly run the guest again, before having restored the host state.
> 
> This includes populating missing fault info, emulating GICv2 CPU
> interface accesses when mapped at unaligned addresses, and emulating
> the GICv3 CPU interface on systems that need it.
> 
> As we are about to have an alternative switch function for VHE systems,
> but VHE systems still need the same early fixup logic, factor out this
> logic into a separate function that can be shared by both switch
> functions.
> 
> No functional change.
> 
> Reviewed-by: Marc Zyngier <marc.zyngier at arm.com>
> Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>

Reviewed-by: Julien Thierry <julien.thierry at arm.com>

> ---
>   arch/arm64/kvm/hyp/switch.c | 99 ++++++++++++++++++++++++---------------------
>   1 file changed, 54 insertions(+), 45 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index 63284647ed11..55ca2e3d42eb 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -270,50 +270,24 @@ static bool __hyp_text __skip_instr(struct kvm_vcpu *vcpu)
>   	}
>   }
>   
> -int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
> +/*
> + * Return true when we were able to fixup the guest exit and should return to
> + * the guest, false when we should restore the host state and return to the
> + * main run loop.
> + */
> +static bool __hyp_text fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
>   {
> -	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! */
> -
>   	/*
>   	 * We're using the raw exception code in order to only process
>   	 * the trap if no SError is pending. We will come back to the
>   	 * same PC once the SError has been injected, and replay the
>   	 * trapping instruction.
>   	 */
> -	if (exit_code == ARM_EXCEPTION_TRAP && !__populate_fault_info(vcpu))
> -		goto again;
> +	if (*exit_code == ARM_EXCEPTION_TRAP && !__populate_fault_info(vcpu))
> +		return true;
>   
>   	if (static_branch_unlikely(&vgic_v2_cpuif_trap) &&
> -	    exit_code == ARM_EXCEPTION_TRAP) {
> +	    *exit_code == ARM_EXCEPTION_TRAP) {
>   		bool valid;
>   
>   		valid = kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_DABT_LOW &&
> @@ -327,9 +301,9 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
>   
>   			if (ret == 1) {
>   				if (__skip_instr(vcpu))
> -					goto again;
> +					return true;
>   				else
> -					exit_code = ARM_EXCEPTION_TRAP;
> +					*exit_code = ARM_EXCEPTION_TRAP;
>   			}
>   
>   			if (ret == -1) {
> @@ -341,29 +315,64 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
>   				 */
>   				if (!__skip_instr(vcpu))
>   					*vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;
> -				exit_code = ARM_EXCEPTION_EL1_SERROR;
> +				*exit_code = ARM_EXCEPTION_EL1_SERROR;
>   			}
> -
> -			/* 0 falls through to be handler out of EL2 */
>   		}
>   	}
>   
>   	if (static_branch_unlikely(&vgic_v3_cpuif_trap) &&
> -	    exit_code == ARM_EXCEPTION_TRAP &&
> +	    *exit_code == ARM_EXCEPTION_TRAP &&
>   	    (kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_SYS64 ||
>   	     kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_CP15_32)) {
>   		int ret = __vgic_v3_perform_cpuif_access(vcpu);
>   
>   		if (ret == 1) {
>   			if (__skip_instr(vcpu))
> -				goto again;
> +				return true;
>   			else
> -				exit_code = ARM_EXCEPTION_TRAP;
> +				*exit_code = ARM_EXCEPTION_TRAP;
>   		}
> -
> -		/* 0 falls through to be handled out of EL2 */
>   	}
>   
> +	/* Return to the host kernel and handle the exit */
> +	return false;
> +}
> +
> +int __hyp_text __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);
> +
> +	do {
> +		/* Jump in the fire! */
> +		exit_code = __guest_enter(vcpu, host_ctxt);
> +
> +		/* And we're baaack! */
> +	} while (fixup_guest_exit(vcpu, &exit_code));
> +
>   	__sysreg_save_guest_state(guest_ctxt);
>   	__sysreg32_save_state(vcpu);
>   	__timer_disable_traps(vcpu);
> 

-- 
Julien Thierry