netdev - RE: [PATCH RFC] pci: Control whether VFs are probed on pci_enable

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Date:	Sun, 7 Dec 2014 20:08:47 +0000
From:	Yuval Mintz <Yuval.Mintz@...gic.com>
To:	Eli Cohen <eli@....mellanox.co.il>
CC:	"bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	David Miller <davem@...emloft.net>,
	linux-pci <linux-pci@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>,
	"ogerlitz@...lanox.com" <ogerlitz@...lanox.com>,
	"yevgenyp@...lanox.com" <yevgenyp@...lanox.com>,
	Donald Dutile <ddutile@...hat.com>
Subject: RE: [PATCH RFC] pci: Control whether VFs are probed on
 pci_enable_sriov

>>>Use a parameter to pci_enable_sriov to control that policy, and modify
>>>all current callers such that they retain the same functionality.
>> 
>> What's the end-game here? How eventually would this be controlled?

>You can probe any VF at the hypervisor through sysfs files
>(bind/unbind). You can also pass them through to a VM. Nothing
>changes.

If you're not planning on adding a logic to set this, why do we need to
add a parameter to pci_enable_sriov() - given that all callers use the
exact same logic?
[And I don't really think we'd want different devices to behave differently
by default; That would be confusing for users.]

>>>Use a one shot flag on struct pci_device which is cleared after the
>>>first probe is ignored so subsequent attempts go through.
>>
>> Does a one-shot flag suffice? E.g., consider assigning a VF to VM and
>> than shutting down the VM. Assuming this feature is disabled,
>> the VF didn't appear on the hypervisor prior to the assignment but
>> will appear after its shutdown.

>Sorry, I don't follow you here. Please clarify.

>To be clear, the functionality proposed here is really one shot. It
>just prevents calling probe once; besides that nothing changes.

What I meant is that device is unbinded after initial probe,
But in the scenario I've stated above, the VF will become binded once
it's returned to the hypervisor.
Now, I understand that what you're trying to achieve - but my question
is whether what you're REALLY trying to achieve is the ability to have VFs
which would only be binded to VMs and never to hypervisor [by default]?--
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