netdev - Re: [PATCH net-next] net: mana: Add a driver for Microsoft Azure Network Adapter (MANA)

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Message-ID: <20210407150030.wvwz6cebxjtjpgfv@liuwe-devbox-debian-v2>
Date:   Wed, 7 Apr 2021 15:00:30 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Haiyang Zhang <haiyangz@...rosoft.com>
Cc:     Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <liuwe@...rosoft.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>
Subject: Re: [PATCH net-next] net: mana: Add a driver for Microsoft Azure
 Network Adapter (MANA)

On Wed, Apr 07, 2021 at 02:34:01PM +0000, Haiyang Zhang wrote:
> 
> 
> > -----Original Message-----
> > From: Wei Liu <wei.liu@...nel.org>
> > Sent: Wednesday, April 7, 2021 9:17 AM
> > To: Dexuan Cui <decui@...rosoft.com>
> > Cc: davem@...emloft.net; kuba@...nel.org; KY Srinivasan
> > <kys@...rosoft.com>; Haiyang Zhang <haiyangz@...rosoft.com>; Stephen
> > Hemminger <sthemmin@...rosoft.com>; wei.liu@...nel.org; Wei Liu
> > <liuwe@...rosoft.com>; netdev@...r.kernel.org; linux-
> > kernel@...r.kernel.org; linux-hyperv@...r.kernel.org
> > Subject: Re: [PATCH net-next] net: mana: Add a driver for Microsoft Azure
> > Network Adapter (MANA)
> > 
> > On Tue, Apr 06, 2021 at 04:23:21PM -0700, Dexuan Cui wrote:
> > [...]
> > > +config MICROSOFT_MANA
> > > +	tristate "Microsoft Azure Network Adapter (MANA) support"
> > > +	default m
> > > +	depends on PCI_MSI
> > > +	select PCI_HYPERV
> > 
> > OOI which part of the code requires PCI_HYPERV?
> > 
> > Asking because I can't immediately find code that looks to be Hyper-V
> > specific (searching for vmbus etc). This device looks like any other PCI devices
> > to me.
> 
> It depends on the VF nic's PCI config space which is presented by the pci_hyperv driver.

I think all it matters is the PCI bus is able to handle the
configuration space access, right? Assuming there is an emulated PCI
root complex which exposes the config space to the driver, will this
driver still work?

I'm trying to understand how tightly coupled with Hyper-V PCI this
driver is. In an alternative universe, Microsft may suddenly decide to
sell this hardware and someone wants to passthrough an VF via VFIO. I
don't see how this driver wouldn't work, hence the original question.

There is no need to change the code. I'm just curious about a tiny
detail in the implementation.

Wei.

> 
> Thanks,
> - Haiyang