Hi Paolo, > -----Original Message----- > From: Paolo Bonzini <pbonz...@redhat.com> > Sent: Wednesday, October 9, 2019 5:13 PM > To: Jianyong Wu (Arm Technology China) <jianyong...@arm.com>; Marc > Zyngier <m...@kernel.org>; net...@vger.kernel.org; yangbo...@nxp.com; > john.stu...@linaro.org; t...@linutronix.de; sean.j.christopher...@intel.com; > richardcoch...@gmail.com; Mark Rutland <mark.rutl...@arm.com>; Will > Deacon <will.dea...@arm.com>; Suzuki Poulose > <suzuki.poul...@arm.com> > Cc: linux-kernel@vger.kernel.org; k...@vger.kernel.org; Steve Capper > <steve.cap...@arm.com>; Kaly Xin (Arm Technology China) > <kaly....@arm.com>; Justin He (Arm Technology China) > <justin...@arm.com>; nd <n...@arm.com>; linux-arm- > ker...@lists.infradead.org > 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 <pbonz...@redhat.com> > >> Sent: Wednesday, October 9, 2019 2:36 PM > >> To: Jianyong Wu (Arm Technology China) <jianyong...@arm.com>; Marc > >> Zyngier <m...@kernel.org>; net...@vger.kernel.org; > yangbo...@nxp.com; > >> john.stu...@linaro.org; t...@linutronix.de; > >> sean.j.christopher...@intel.com; richardcoch...@gmail.com; Mark > >> Rutland <mark.rutl...@arm.com>; Will Deacon > <will.dea...@arm.com>; > >> Suzuki Poulose <suzuki.poul...@arm.com> > >> Cc: linux-kernel@vger.kernel.org; k...@vger.kernel.org; Steve Capper > >> <steve.cap...@arm.com>; Kaly Xin (Arm Technology China) > >> <kaly....@arm.com>; Justin He (Arm Technology China) > >> <justin...@arm.com>; nd <n...@arm.com>; linux-arm- > >> ker...@lists.infradead.org > >> 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
