[PATCH v7 14/16] KVM: arm64: Remove redundant *exit_code changes in fpsimd_guest_exit()

[Christoffer Dall]

On Wed, May 09, 2018 at 05:13:03PM +0100, Dave Martin wrote:
> In fixup_guest_exit(), there are a couple of cases where after
> checking what the exit code was, we assign it explicitly with the
> value it already had.
> 
> Assuming this is not indicative of a bug, these assignments are not
> needed.
> 
> This patch removes the redundant assignments, and simplifies some
> if-nesting that becomes trivial as a result.
> 
> No functional change.
> 
> Signed-off-by: Dave Martin <Dave.Martin at arm.com>
> Acked-by: Marc Zyngier <marc.zyngier at arm.com>
> ---
>  arch/arm64/kvm/hyp/switch.c | 16 ++++------------
>  1 file changed, 4 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index a6a8c7d..18d0faa 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -403,12 +403,8 @@ static bool __hyp_text fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
>  		if (valid) {
>  			int ret = __vgic_v2_perform_cpuif_access(vcpu);
>  
> -			if (ret == 1) {
> -				if (__skip_instr(vcpu))
> -					return true;
> -				else
> -					*exit_code = ARM_EXCEPTION_TRAP;
> -			}
> +			if (ret ==  1 && __skip_instr(vcpu))
> +				return true;
>  
>  			if (ret == -1) {
>  				/* Promote an illegal access to an
> @@ -430,12 +426,8 @@ static bool __hyp_text fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
>  	     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))
> -				return true;
> -			else
> -				*exit_code = ARM_EXCEPTION_TRAP;
> -		}
> +		if (ret == 1 && __skip_instr(vcpu))
> +			return true;
>  	}
>  
>  	/* Return to the host kernel and handle the exit */

I can't seem to easily convince myself that we couldn't have the
ARM_EXIT_WITH_SERROR_BIT set here and thus instead should be using
ARM_EXCEPTION_CODE() in the upper check.

Marc, can you help?

Thanks,
-Christoffer