netdev - Re: [net-next 10/10] net/mlx5e: Add support for PCI relaxed ordering

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Message-ID: <19a722952a2b91cc3b26076b8fd74afdfbfaa7a4.camel@mellanox.com>
Date:   Wed, 24 Jun 2020 20:15:14 +0000
From:   Saeed Mahameed <saeedm@...lanox.com>
To:     Aya Levin <ayal@...lanox.com>, "kuba@...nel.org" <kuba@...nel.org>
CC:     "mkubecek@...e.cz" <mkubecek@...e.cz>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "helgaas@...nel.org" <helgaas@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Tariq Toukan <tariqt@...lanox.com>,
        "alexander.h.duyck@...ux.intel.com" 
        <alexander.h.duyck@...ux.intel.com>
Subject: Re: [net-next 10/10] net/mlx5e: Add support for PCI relaxed ordering

On Wed, 2020-06-24 at 10:22 -0700, Jakub Kicinski wrote:
> On Wed, 24 Jun 2020 10:34:40 +0300 Aya Levin wrote:
> > > > I think Michal will rightly complain that this does not belong
> > > > in
> > > > private flags any more. As (/if?) ARM deployments take a
> > > > foothold
> > > > in DC this will become a common setting for most NICs.  
> > > 
> > > Initially we used pcie_relaxed_ordering_enabled() to
> > >   programmatically enable this on/off on boot but this seems to
> > > introduce some degradation on some Intel CPUs since the Intel
> > > Faulty
> > > CPUs list is not up to date. Aya is discussing this with Bjorn.  
> > Adding Bjorn Helgaas
> 
> I see. Simply using pcie_relaxed_ordering_enabled() and blacklisting
> bad CPUs seems far nicer from operational perspective. Perhaps Bjorn
> will chime in. Pushing the validation out to the user is not a great
> solution IMHO.
> 

Can we move on with this patch for now ? since we are going to keep the
user knob anyway, what is missing is setting the default value
automatically but this can't be done until we
fix pcie_relaxed_ordering_enabled()