netdev - Re: [EXTERNAL] RE: [PATCH net] i40e/iavf: Fix msg interface between VF and PF

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Message-ID: <d078d3efc784805a67ba1a1c6e94fb4ec1c0aec6.camel@intel.com>
Date:   Thu, 07 Nov 2019 11:38:55 -0800
From:   Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:     Arkady Gilinsky <arkady.gilinsky@...monicinc.com>,
        "Creeley, Brett" <brett.creeley@...el.com>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Cc:     Arkady Gilinsky <arcadyg@...il.com>
Subject: Re: [EXTERNAL] RE: [PATCH net] i40e/iavf: Fix msg interface between
 VF and PF

On Wed, 2019-11-06 at 05:30 +0000, Arkady Gilinsky wrote:
> On Tue, 2019-11-05 at 16:55 +0000, Creeley, Brett wrote:
> > > -----Original Message-----
> > > From: Arkady Gilinsky <arkady.gilinsky@...monicinc.com>
> > > Sent: Monday, November 4, 2019 9:24 PM
> > > To: Creeley, Brett <brett.creeley@...el.com>; 
> > > intel-wired-lan@...ts.osuosl.org; netdev@...r.kernel.org; Kirsher,
> > > Jeffrey T
> > > <jeffrey.t.kirsher@...el.com>
> > > Cc: Arkady Gilinsky <arcadyg@...il.com>
> > > Subject: Re: [EXTERNAL] RE: [PATCH net] i40e/iavf: Fix msg interface
> > > between VF and PF
> > > > static bool i40e_vc_verify_vqs_bitmaps(struct virtchnl_queue_select
> > > > *vqs)
> > > > {
> > > >    /* this will catch any changes made to the virtchnl_queue_select
> > > > bitmap */
> > > >    if (sizeof(vqs->rx_queues) != sizeof(u32) ||
> > > >         sizeof(vqs->tx_queues) != sizeof(u32))
> > > >            return false;
> > > 
> > > If so, then is it better to check the type of the fields in compile-
> > > time rather than in runtime ?
> > > Something like this:
> > > BUILD_BUG_ON(sizeof(vqs->rx_queues) != sizeof(u32));
> > > BUILD_BUG_ON(sizeof(vqs->tx_queues) != sizeof(u32));
> > > This is not required comparison each time when function is called and
> > > made code more optimized.
> > 
> > I don't think this is required with the change you suggested below.
> Agree.
> If other code in driver not need to be adjusted/verified, then this check
> is not needed.
> > > >    if ((vqs->rx_queues == 0 && vqs->tx_queues == 0) ||
> > > >          hweight32(vqs->rx_queues) > I40E_MAX_VF_QUEUES ||
> > > >          hweight32(vqs->tx_queues) > I40E_MAX_VF_QUEUES)
> > > >            return false;
> > > 
> > > Again, from optimization POV it is better to have constant changed
> > > than variable,
> > > since it is compile time and not run time action:
> > >      if ((vqs->rx_queues == 0 && vqs->tx_queues == 0) ||
> > >            vqs->rx_queues >= (BIT(I40E_MAX_VF_QUEUES)) ||
> > > 
> > >       vqs->tx_queues >= (BIT(I40E_MAX_VF_QUEUES)))
> > >              return false;
> > 
> > This seems much better than my solution. It fixes the original issue,
> > handles if the
> > vqs->[r|t]x_queues variables have changed in size, and the queue bitmap
> > comparison
> > uses a constant. Thanks!
> Thanks to you for feedback.
> I am trying to understand if this patch will enter into official kernel
> tree
> and, not less important from my POV, to official Intel drivers.
> Brett/Jeffrey, could you, please, assist to make sure that this fix, or
> fix suggested by Brett,
> will be integrated into Intel i40e/iavf drivers ?
> Or may be I should write mail straight to Intel support ?

As Brett pointed out, there are issues with this patch. Please make the
suggested changes and re-submit the patch to 
intel-wired-lan@...ts.osuosl.org

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