> -----Original Message----- > From: Marc Zyngier <maz@xxxxxxxxxx> > Sent: Monday, September 7, 2020 5:47 PM > To: Jianyong Wu <Jianyong.Wu@xxxxxxx> > Cc: netdev@xxxxxxxxxxxxxxx; yangbo.lu@xxxxxxx; john.stultz@xxxxxxxxxx; > tglx@xxxxxxxxxxxxx; pbonzini@xxxxxxxxxx; sean.j.christopherson@xxxxxxxxx; > richardcochran@xxxxxxxxx; Mark Rutland <Mark.Rutland@xxxxxxx>; > will@xxxxxxxxxx; Suzuki Poulose <Suzuki.Poulose@xxxxxxx>; Steven Price > <Steven.Price@xxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; linux-arm- > kernel@xxxxxxxxxxxxxxxxxxx; kvmarm@xxxxxxxxxxxxxxxxxxxxx; > kvm@xxxxxxxxxxxxxxx; Steve Capper <Steve.Capper@xxxxxxx>; Justin He > <Justin.He@xxxxxxx>; nd <nd@xxxxxxx> > Subject: Re: [PATCH v14 08/10] ptp: arm64: Enable ptp_kvm for arm64 > > On 2020-09-07 10:28, Jianyong Wu wrote: > >> -----Original Message----- > >> From: Marc Zyngier <maz@xxxxxxxxxx> > >> Sent: Monday, September 7, 2020 4:55 PM > >> To: Jianyong Wu <Jianyong.Wu@xxxxxxx> > > [...] > > >> >> arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_FEATUR > >> >> ES_FUNC_ID, > >> >> > + &hvc_res); > >> >> > + if (!(hvc_res.a0 | BIT(ARM_SMCCC_KVM_FUNC_KVM_PTP))) > >> >> > + return -EOPNOTSUPP; > >> >> > + > >> >> > + return 0; > >> >> > >> >> What happens if the > >> >> ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID function isn't > >> implemented > >> >> (on an old kernel or a non-KVM hypervisor)? The expected behaviour > >> >> is that a0 will contain SMCCC_RET_NOT_SUPPORTED, which is -1. > >> >> The result is that this function always returns "supported". Not > >> >> an acceptable behaviour. > >> >> > >> > Oh! it's really a stupid mistake, should be "&" not "|". > >> > >> But even then. (-1 & whatever) is always true. > > > > Yeah, what about checking if a0 is non-negative first? Like: > > if (hvc_res.a0 < 0 || !(hvc_res.a0 & > BIT(ARM_SMCCC_KVM_FUNC_KVM_PTP))) > > return -EOPNOTSUPP; > > I don't get it. You already carry a patch from Will that gives you a way to check > for a service (kvm_arm_hyp_service_available()). > > Why do you need to reinvent the wheel? Sorry, I should have changed this code according to Will's patch. Thanks for reminder! Thanks jianyong > > M. > -- > Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
