KVM: arm64: Remove S1PTW check from kvm_vcpu_dabt_iswrite()

Now that kvm_vcpu_trap_is_write_fault() checks for S1PTW, there
is no need for kvm_vcpu_dabt_iswrite() to do the same thing, as
we already check for this condition on all existing paths.

Drop the check and add a comment instead.
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20200915104218.1284701-3-maz@kernel.org

arch/arm64/include/asm/kvm_emulate.h

@@ -303,10 +303,10 @@ static __always_inline bool kvm_vcpu_abt_iss1tw(const struct kvm_vcpu *vcpu)
 	return !!(kvm_vcpu_get_esr(vcpu) & ESR_ELx_S1PTW);
 }
 
+/* Always check for S1PTW *before* using this. */
 static __always_inline bool kvm_vcpu_dabt_iswrite(const struct kvm_vcpu *vcpu)
 {
-	return !!(kvm_vcpu_get_esr(vcpu) & ESR_ELx_WNR) ||
-		kvm_vcpu_abt_iss1tw(vcpu); /* AF/DBM update */
+	return kvm_vcpu_get_esr(vcpu) & ESR_ELx_WNR;
 }
 
 static inline bool kvm_vcpu_dabt_is_cm(const struct kvm_vcpu *vcpu)