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

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Message-ID: <5484C77D.7060501@redhat.com>
Date:	Sun, 07 Dec 2014 16:32:45 -0500
From:	Don Dutile <ddutile@...hat.com>
To:	Yuval Mintz <Yuval.Mintz@...gic.com>,
	Eli Cohen <eli@....mellanox.co.il>,
	"bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	David Miller <davem@...emloft.net>
CC:	linux-pci <linux-pci@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>,
	"ogerlitz@...lanox.com" <ogerlitz@...lanox.com>,
	"yevgenyp@...lanox.com" <yevgenyp@...lanox.com>,
	Eli Cohen <eli@...lanox.com>
Subject: Re: [PATCH RFC] pci: Control whether VFs are probed on pci_enable_sriov

On 12/07/2014 12:05 PM, Yuval Mintz wrote:
>
>> This can save host side resource usage by VF instances which would be
>> eventually probed to VMs.
>
>> 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?
>
>> 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.
>
+1 to this question.
All I see is a one-shot savings in VF configuration time at pci_sriov_enable() time.
Please explain why this is so important for mlx5 (sriov) operation?

Can the vf driver probe be called & exit early the first time, and perform full
(host) configuration thereafter?

- Don
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