linux-kernel - Re: [PATCH v19 6/7] KVM: arm64: Add support for the KVM PTP service

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Message-ID: <5aadf0b4-b9e5-8521-db60-52a0f319cf28@huawei.com>
Date:   Sat, 17 Apr 2021 16:59:39 +0800
From:   Zenghui Yu <yuzenghui@...wei.com>
To:     Marc Zyngier <maz@...nel.org>
CC:     <netdev@...r.kernel.org>, <yangbo.lu@....com>,
        <john.stultz@...aro.org>, <tglx@...utronix.de>,
        <pbonzini@...hat.com>, <seanjc@...gle.com>,
        <richardcochran@...il.com>, <Mark.Rutland@....com>,
        <will@...nel.org>, <suzuki.poulose@....com>,
        <Andre.Przywara@....com>, <steven.price@....com>,
        <lorenzo.pieralisi@....com>, <sudeep.holla@....com>,
        <justin.he@....com>, <kvm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <kernel-team@...roid.com>,
        <kvmarm@...ts.cs.columbia.edu>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v19 6/7] KVM: arm64: Add support for the KVM PTP service

On 2021/3/30 22:54, Marc Zyngier wrote:
> +PTP_KVM support for arm/arm64
> +=============================
> +
> +PTP_KVM is used for high precision time sync between host and guests.
> +It relies on transferring the wall clock and counter value from the
> +host to the guest using a KVM-specific hypercall.
> +
> +* ARM_SMCCC_HYP_KVM_PTP_FUNC_ID: 0x86000001

Per include/linux/arm-smccc.h, this should be
ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID.

> +
> +This hypercall uses the SMC32/HVC32 calling convention:
> +
> +ARM_SMCCC_HYP_KVM_PTP_FUNC_ID

ditto

> +    =============    ==========    ==========
> +    Function ID:     (uint32)      0x86000001
> +    Arguments:       (uint32)      KVM_PTP_VIRT_COUNTER(0)
> +                                   KVM_PTP_PHYS_COUNTER(1)