netdev - Re: [PATCH iwl-next] ice: store VF's pci_dev ptr in ice

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Date: Mon, 21 Aug 2023 12:48:40 +0200
From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
To: Leon Romanovsky <leon@...nel.org>
CC: Tony Nguyen <anthony.l.nguyen@...el.com>, Jesse Brandeburg
	<jesse.brandeburg@...el.com>, <intel-wired-lan@...ts.osuosl.org>,
	<netdev@...r.kernel.org>, Mateusz Polchlopek <mateusz.polchlopek@...el.com>,
	Jacob Keller <jacob.e.keller@...el.com>
Subject: Re: [PATCH iwl-next] ice: store VF's pci_dev ptr in ice_vf

On 8/18/23 20:20, Leon Romanovsky wrote:
> On Fri, Aug 18, 2023 at 02:20:51PM +0200, Przemek Kitszel wrote:
>> On 8/16/23 16:31, Leon Romanovsky wrote:
>>> On Wed, Aug 16, 2023 at 04:54:54AM -0400, Przemek Kitszel wrote:
>>>> Extend struct ice_vf by vfdev.
>>>> Calculation of vfdev falls more nicely into ice_create_vf_entries().
>>>>
>>>> Caching of vfdev enables simplification of ice_restore_all_vfs_msi_state().
>>>
>>> I see that old code had access to pci_dev * of VF without any locking
>>> from concurrent PCI core access. How is it protected? How do you make
>>> sure that vfdev is valid?
>>>
>>> Generally speaking, it is rarely good idea to cache VF pci_dev pointers
>>> inside driver.
>>>
>>> Thanks
>>
>> Overall, I do agree that ice driver, as a whole, has room for improvement in
>> terms of synchronization, objects lifetime, and similar.
>>
>> In this particular case, I don't see any reason of PCI reconfiguration
>> during VF lifetime, but likely I'm missing something?
> 
> You are caching VF pointer in PF, 

that's correct that the driver is PF/ice

> and you are subjected to PF lifetime
> and not VF lifetime.

this belongs to struct ice_vf, which should have VF lifetime,
otherwise it's already at risk

> 
> Thanks

Thank you!