linux-kernel - Re: [PATCH 8/9] vfio/pci: use x86 naming instead of igd

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Date:   Fri, 5 Feb 2021 11:42:11 +1100
From:   Alexey Kardashevskiy <aik@...abs.ru>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     Max Gurtovoy <mgurtovoy@...dia.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, liranl@...dia.com, oren@...dia.com,
        tzahio@...dia.com, leonro@...dia.com, yarong@...dia.com,
        aviadye@...dia.com, shahafs@...dia.com, artemp@...dia.com,
        kwankhede@...dia.com, ACurrid@...dia.com, gmataev@...dia.com,
        cjia@...dia.com, yishaih@...dia.com
Subject: Re: [PATCH 8/9] vfio/pci: use x86 naming instead of igd



On 04/02/2021 23:51, Jason Gunthorpe wrote:
> On Thu, Feb 04, 2021 at 12:05:22PM +1100, Alexey Kardashevskiy wrote:
> 
>> It is system firmware (==bios) which puts stuff in the device tree. The
>> stuff is:
>> 1. emulated pci devices (custom pci bridges), one per nvlink, emulated by
>> the firmware, the driver is "ibmnpu" and it is a part on the nvidia driver;
>> these are basically config space proxies to the cpu's side of nvlink.
>> 2. interconnect information - which of 6 gpus nvlinks connected to which
>> nvlink on the cpu side, and memory ranges.
> 
> So what is this vfio_nvlink driver supposed to be bound to?
> 
> The "emulated pci devices"?

Yes.

> A real GPU function?

Yes.

> A real nvswitch function?

What do you mean by this exactly? The cpu side of nvlink is "emulated 
pci devices", the gpu side is not in pci space at all, the nvidia driver 
manages it via the gpu's mmio or/and cfg space.

> Something else?

Nope :)
In this new scheme which you are proposing it should be 2 drivers, I guess.

> 
> Jason
> 

-- 
Alexey