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

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Date: Fri, 18 Aug 2023 21:20:59 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Przemek Kitszel <przemyslaw.kitszel@...el.com>
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 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, and you are subjected to PF lifetime
and not VF lifetime.

Thanks