Re: [PATCH net-next v4] ptp: add Alibaba CIPU PTP clock driver

[Wen Gu <guwen@linux.alibaba.com>]

On 2025/8/22 15:43, David Woodhouse wrote:
> On Fri, 2025-08-22 at 10:07 +0800, Wen Gu wrote:
>>
>> Hi David,
>>
>> How does vmclock work in a bare‑metal scenario, given that there is no
>> guest–hypervisor architecture?
>>
>> You mentioned "vmclock over PCI", do you mean passing a PCI device to the
>> bare‑metal? What is this PCI device, and which driver does it use?
> 

Hi David, sorry for the late reply, my mailbox misclassified this mail.

> It would need PCIe PTM to synchronize against the host's arch timer or
> TSC, which you said you don't have on the CIPU. We don't have PTM
> either, so there is no existing defined PCI device.
> 

I see. that's what I thought, in our scenario VM and bare metal can not
use a unified way based on vmclock to achieve PTP clock currently.

> I'm in the process of writing up a specification for the vmclock
> device. It doesn't really contain much information that isn't already
> in the QEMU and Linux code; it'll just be an easier way to find it
> rather than reading GPL'd code, which is problematic for some.
> 
> I *could* add a PCI transport, but I figured it was easy enough to do
> that later if anyone implements one.

Understood, thanks for the update.