linux-kernel - Re: [PATCH RESEND] ptp: add VMware virtual PTP clock driver

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Message-Id: <20200304.140410.731261448085906331.davem@davemloft.net>
Date:   Wed, 04 Mar 2020 14:04:10 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     vithampi@...are.com
Cc:     richardcochran@...il.com, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, Pv-drivers@...are.com,
        virtualization@...ts.linux-foundation.org, x86@...nel.org,
        thellstrom@...are.com, jgross@...e.com
Subject: Re: [PATCH RESEND] ptp: add VMware virtual PTP clock driver

From: Vivek Thampi <vithampi@...are.com>
Date: Fri, 28 Feb 2020 05:32:46 +0000

> Add a PTP clock driver called ptp_vmw, for guests running on VMware ESXi
> hypervisor. The driver attaches to a VMware virtual device called
> "precision clock" that provides a mechanism for querying host system time.
> Similar to existing virtual PTP clock drivers (e.g. ptp_kvm), ptp_vmw
> utilizes the kernel's PTP hardware clock API to implement a clock device
> that can be used as a reference in Chrony for synchronizing guest time with
> host.
> 
> The driver is only applicable to x86 guests running in VMware virtual
> machines with precision clock virtual device present. It uses a VMware
> specific hypercall mechanism to read time from the device.
> 
> Reviewed-by: Thomas Hellstrom <thellstrom@...are.com>
> Signed-off-by: Vivek Thampi <vithampi@...are.com>
> ---
>  Based on feedback, resending patch to include a broader audience.

If it's just providing a read of an accurate timesource, I think it's kinda
pointless to provide a full PTP driver for it.