On Tue, May 22, 2018 at 05:05:18PM +0100, Dave Martin wrote:
> The entire tail of fixup_guest_exit() is contained in if statements
> of the form if (x && *exit_code == ARM_EXCEPTION_TRAP). As a result,
> we can check just once and bail out of the function early, allowing
> the remaining if conditions to be simplified.
>
> The only awkward case is where *exit_code is changed to
> ARM_EXCEPTION_EL1_SERROR in the case of an illegal GICv2 CPU
> interface access: in that case, the GICv3 trap handling code is
> skipped using a goto. This avoids pointlessly evaluating the
> static branch check for the GICv3 case, even though we can't have
> vgic_v2_cpuif_trap and vgic_v3_cpuif_trap true simultaneously
> unless we have a GICv3 and GICv2 on the host: that sounds stupid,
> but I haven't satisfied myself that it can't happen.
>
> No functional change.
Acked-by: Christoffer Dall <christoffer.dall@xxxxxxx>
>
> Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx>
> Reviewed-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> arch/arm64/kvm/hyp/switch.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index 18d0faa..4fbee95 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -387,11 +387,13 @@ static bool __hyp_text fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
> * same PC once the SError has been injected, and replay the
> * trapping instruction.
> */
> - if (*exit_code == ARM_EXCEPTION_TRAP && !__populate_fault_info(vcpu))
> + if (*exit_code != ARM_EXCEPTION_TRAP)
> + goto exit;
> +
> + if (!__populate_fault_info(vcpu))
> return true;
>
> - if (static_branch_unlikely(&vgic_v2_cpuif_trap) &&
> - *exit_code == ARM_EXCEPTION_TRAP) {
> + if (static_branch_unlikely(&vgic_v2_cpuif_trap)) {
> bool valid;
>
> valid = kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_DABT_LOW &&
> @@ -417,11 +419,12 @@ static bool __hyp_text fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
> *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;
> *exit_code = ARM_EXCEPTION_EL1_SERROR;
> }
> +
> + goto exit;
> }
> }
>
> if (static_branch_unlikely(&vgic_v3_cpuif_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);
> @@ -430,6 +433,7 @@ static bool __hyp_text fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
> return true;
> }
>
> +exit:
> /* Return to the host kernel and handle the exit */
> return false;
> }
> --
> 2.1.4
>
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