KVM: arm64: Fold redundant exit code checks out of fixup_guest_exit()

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.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index 18d0faa..4fbee95 100644 (file)
--- 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;
 }