linux-kernel - RE: [PATCH v14 09/10] doc: add ptp_kvm introduction for arm64 support

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Message-ID: <HE1PR0802MB2555849BDD0F9185ED3CF5F7F4280@HE1PR0802MB2555.eurprd08.prod.outlook.com>
Date:   Mon, 7 Sep 2020 07:55:38 +0000
From:   Jianyong Wu <Jianyong.Wu@....com>
To:     Marc Zyngier <maz@...nel.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "yangbo.lu@....com" <yangbo.lu@....com>,
        "john.stultz@...aro.org" <john.stultz@...aro.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "sean.j.christopherson@...el.com" <sean.j.christopherson@...el.com>,
        "richardcochran@...il.com" <richardcochran@...il.com>,
        Mark Rutland <Mark.Rutland@....com>,
        "will@...nel.org" <will@...nel.org>,
        Suzuki Poulose <Suzuki.Poulose@....com>,
        Steven Price <Steven.Price@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "kvmarm@...ts.cs.columbia.edu" <kvmarm@...ts.cs.columbia.edu>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        Steve Capper <Steve.Capper@....com>,
        Justin He <Justin.He@....com>, nd <nd@....com>
Subject: RE: [PATCH v14 09/10] doc: add ptp_kvm introduction for arm64 support

Hi Marc,

> -----Original Message-----
> From: Marc Zyngier <maz@...nel.org>
> Sent: Saturday, September 5, 2020 12:19 AM
> To: Jianyong Wu <Jianyong.Wu@....com>
> Cc: netdev@...r.kernel.org; yangbo.lu@....com; john.stultz@...aro.org;
> tglx@...utronix.de; pbonzini@...hat.com; sean.j.christopherson@...el.com;
> richardcochran@...il.com; Mark Rutland <Mark.Rutland@....com>;
> will@...nel.org; Suzuki Poulose <Suzuki.Poulose@....com>; Steven Price
> <Steven.Price@....com>; linux-kernel@...r.kernel.org; linux-arm-
> kernel@...ts.infradead.org; kvmarm@...ts.cs.columbia.edu;
> kvm@...r.kernel.org; Steve Capper <Steve.Capper@....com>; Justin He
> <Justin.He@....com>; nd <nd@....com>
> Subject: Re: [PATCH v14 09/10] doc: add ptp_kvm introduction for arm64
> support
> 
> On Fri, 04 Sep 2020 10:27:43 +0100,
> Jianyong Wu <jianyong.wu@....com> wrote:
> >
> > ptp_kvm implementation depends on hypercall using SMCCC. So we
> > introduce a new SMCCC service ID. This doc explain how we define and
> > use this new ID.
> >
> > Signed-off-by: Jianyong Wu <jianyong.wu@....com>
> > ---
> >  Documentation/virt/kvm/arm/ptp_kvm.rst | 72
> > ++++++++++++++++++++++++++
> >  1 file changed, 72 insertions(+)
> >  create mode 100644 Documentation/virt/kvm/arm/ptp_kvm.rst
> >
> > diff --git a/Documentation/virt/kvm/arm/ptp_kvm.rst
> > b/Documentation/virt/kvm/arm/ptp_kvm.rst
> > new file mode 100644
> > index 000000000000..455591e2587a
> > --- /dev/null
> > +++ b/Documentation/virt/kvm/arm/ptp_kvm.rst
> > @@ -0,0 +1,72 @@
> > +.. SPDX-License-Identifier: GPL-2.0
> > +
> > +PTP_KVM support for arm64
> > +=========================
> > +
> > +PTP_KVM is used for time sync between guest and host in a high precison.
> > +It needs get wall time and counter value from host and transfer these
> > +data to guest via hypercall service. So one more hypercall service
> > +should be added.
> > +
> > +This new SMCCC hypercall will be defined as:
> > +
> > +* ARM_SMCCC_HYP_KVM_PTP_FUNC_ID: 0xC6000001
> > +
> > +As we only support 64-bits ptp_kvm client, so we choose SMC64/HVC64
> > +calling convention.
> 
> This isn't what the code does, as it is explicitly set as an SMC32 service...
> Furthermore, we still run 32bit guests, and will do for the foreseeable future.
> Having removed KVM support for 32bit doesn't mean 32bits are gone.

Sorry to have removed arm32 support. It's worthy to add arm32 support in.
I will add it next time.

Thanks
Jianyong 

> 
> 	M.
> 
> --
> Without deviation from the norm, progress is not possible.