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SubjectRE: [PATCH v14 09/10] doc: add ptp_kvm introduction for arm64 support
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Hi Marc,

> -----Original Message-----
> From: Marc Zyngier <maz@kernel.org>
> Sent: Saturday, September 5, 2020 12:19 AM
> To: Jianyong Wu <Jianyong.Wu@arm.com>
> Cc: netdev@vger.kernel.org; yangbo.lu@nxp.com; john.stultz@linaro.org;
> tglx@linutronix.de; pbonzini@redhat.com; sean.j.christopherson@intel.com;
> richardcochran@gmail.com; Mark Rutland <Mark.Rutland@arm.com>;
> will@kernel.org; Suzuki Poulose <Suzuki.Poulose@arm.com>; Steven Price
> <Steven.Price@arm.com>; linux-kernel@vger.kernel.org; linux-arm-
> kernel@lists.infradead.org; kvmarm@lists.cs.columbia.edu;
> kvm@vger.kernel.org; Steve Capper <Steve.Capper@arm.com>; Justin He
> <Justin.He@arm.com>; nd <nd@arm.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@arm.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@arm.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.

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