netdev - Re: [RFC PATCH v3 4/6] psci: Add hvc call service for ptp

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Date:   Wed, 18 Sep 2019 10:25:37 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Jianyong Wu <jianyong.wu@....com>, netdev@...r.kernel.org,
        yangbo.lu@....com, john.stultz@...aro.org, tglx@...utronix.de,
        sean.j.christopherson@...el.com, maz@...nel.org,
        richardcochran@...il.com, Mark.Rutland@....com,
        Will.Deacon@....com, suzuki.poulose@....com
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Steve.Capper@....com, Kaly.Xin@....com, justin.he@....com,
        nd@....com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH v3 4/6] psci: Add hvc call service for ptp_kvm.

On 18/09/19 10:07, Jianyong Wu wrote:
> +	case ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID:
> +		getnstimeofday(ts);

This is not Y2038-safe.  Please use ktime_get_real_ts64 instead, and
split the 64-bit seconds value between val[0] and val[1].

However, it seems to me that the new function is not needed and you can
just use ktime_get_snapshot.  You'll get the time in
systime_snapshot->real and the cycles value in systime_snapshot->cycles.

> +		get_current_counterval(&sc);
> +		val[0] = ts->tv_sec;
> +		val[1] = ts->tv_nsec;
> +		val[2] = sc.cycles;
> +		val[3] = 0;
> +		break;

This should return a guest-cycles value.  If the cycles values always
the same between the host and the guest on ARM, then okay.  If not, you
have to apply whatever offset exists.

Thanks,

Paolo