Hi Paolo, > -----Original Message----- > From: Paolo Bonzini <pbonzini@xxxxxxxxxx> > Sent: Wednesday, October 9, 2019 5:13 PM > To: Jianyong Wu (Arm Technology China) <Jianyong.Wu@xxxxxxx>; Marc > Zyngier <maz@xxxxxxxxxx>; netdev@xxxxxxxxxxxxxxx; yangbo.lu@xxxxxxx; > john.stultz@xxxxxxxxxx; tglx@xxxxxxxxxxxxx; sean.j.christopherson@xxxxxxxxx; > richardcochran@xxxxxxxxx; Mark Rutland <Mark.Rutland@xxxxxxx>; Will > Deacon <Will.Deacon@xxxxxxx>; Suzuki Poulose > <Suzuki.Poulose@xxxxxxx> > Cc: linux-kernel@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; Steve Capper > <Steve.Capper@xxxxxxx>; Kaly Xin (Arm Technology China) > <Kaly.Xin@xxxxxxx>; Justin He (Arm Technology China) > <Justin.He@xxxxxxx>; nd <nd@xxxxxxx>; linux-arm- > kernel@xxxxxxxxxxxxxxxxxxx > Subject: Re: [RFC PATCH v3 4/6] psci: Add hvc call service for ptp_kvm. > > On 09/10/19 10:18, Jianyong Wu (Arm Technology China) wrote: > > Hi Paolo, > > > >> -----Original Message----- > >> From: Paolo Bonzini <pbonzini@xxxxxxxxxx> > >> Sent: Wednesday, October 9, 2019 2:36 PM > >> To: Jianyong Wu (Arm Technology China) <Jianyong.Wu@xxxxxxx>; Marc > >> Zyngier <maz@xxxxxxxxxx>; netdev@xxxxxxxxxxxxxxx; > yangbo.lu@xxxxxxx; > >> john.stultz@xxxxxxxxxx; tglx@xxxxxxxxxxxxx; > >> sean.j.christopherson@xxxxxxxxx; richardcochran@xxxxxxxxx; Mark > >> Rutland <Mark.Rutland@xxxxxxx>; Will Deacon > <Will.Deacon@xxxxxxx>; > >> Suzuki Poulose <Suzuki.Poulose@xxxxxxx> > >> Cc: linux-kernel@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; Steve Capper > >> <Steve.Capper@xxxxxxx>; Kaly Xin (Arm Technology China) > >> <Kaly.Xin@xxxxxxx>; Justin He (Arm Technology China) > >> <Justin.He@xxxxxxx>; nd <nd@xxxxxxx>; linux-arm- > >> kernel@xxxxxxxxxxxxxxxxxxx > >> Subject: Re: [RFC PATCH v3 4/6] psci: Add hvc call service for ptp_kvm. > >> > >> On 09/10/19 07:21, Jianyong Wu (Arm Technology China) wrote: > >>> As ptp_kvm clock has fixed to arm arch system counter in patch set > >>> v4, we need check if the current clocksource is system counter when > >>> return clock cycle in host, so a helper needed to return the current > >>> clocksource. Could I add this helper in next patch set? > >> > >> You don't need a helper. You need to return the ARM arch counter > >> clocksource in the struct system_counterval_t that you return. > >> get_device_system_crosststamp will then check that the clocksource > >> matches the active one. > > > > We must ensure both of the host and guest using the same clocksource. > > get_device_system_crosststamp will check the clocksource of guest and > > we also need check the clocksource in host, and struct type can't be > transferred from host to guest using arm hypercall. > > now we lack of a mechanism to check the current clocksource. I think this > will be useful if we add one. > > Got it---yes, I think adding a struct clocksource to struct > system_time_snapshot would make sense. Then the hypercall can just use > ktime_get_snapshot and fail if the clocksource is not the ARM arch counter. > > John (Stultz), does that sound good to you? The context is that Jianyong > would like to add a hypercall that returns a (cycles, > nanoseconds) pair to the guest. On x86 we're relying on the vclock_mode > field that is already there for the vDSO, but being able to just use > ktime_get_snapshot would be much nicer. > Could I add struct clocksource to system_time_snapshot struct in next version of my patch set? Jianyong Wu Thanks > Paolo
