From: Saeed Mahameed <saeedm@mellanox.com>
To: "jgg@nvidia.com" <jgg@nvidia.com>, "kuba@kernel.org" <kuba@kernel.org>
Cc: "mkubecek@suse.cz" <mkubecek@suse.cz>,
Aya Levin <ayal@mellanox.com>,
"davem@davemloft.net" <davem@davemloft.net>,
Tariq Toukan <tariqt@mellanox.com>,
"alexander.h.duyck@linux.intel.com"
<alexander.h.duyck@linux.intel.com>,
"jonathan.lemon@gmail.com" <jonathan.lemon@gmail.com>,
"helgaas@kernel.org" <helgaas@kernel.org>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>
Subject: Re: [net-next 10/10] net/mlx5e: Add support for PCI relaxed ordering
Date: Fri, 10 Jul 2020 02:18:02 +0000 [thread overview]
Message-ID: <64f58446adb2536f87ea13cc5f0a88cd77d5cd5b.camel@mellanox.com> (raw)
In-Reply-To: <20200709124726.24315b6e@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
On Thu, 2020-07-09 at 12:47 -0700, Jakub Kicinski wrote:
> On Thu, 9 Jul 2020 15:20:11 -0300 Jason Gunthorpe wrote:
> > > 2) having the driver set RO on the transactions it initiates,
> > > which
> > > are honored iff the PCI bit is set.
> > >
> > > It seems that in addition to the PCI core changes, there still is
> > > a need
> > > for driver controls? Unless the driver always enables RO if it's
> > > capable?
> >
> > I think the PCI spec imagined that when the config space RO bit was
> > enabled the PCI device would just start using RO packets, in an
> > appropriate and device specific way.
> >
> > So the fine grained control in #2 is something done extra by some
> > devices.
> >
> > IMHO if the driver knows it is functionally correct with RO then it
> > should enable it fully on the device when the config space bit is
> > set.
> >
> > I'm not sure there is a reason to allow users to finely tune RO, at
> > least I haven't heard of cases where RO is a degredation depending
> > on
> > workload.
> >
> > If some platform doesn't work when RO is turned on then it should
> > be
> > globally black listed like is already done in some cases.
> >
> > If the devices has bugs and uses RO wrong, or the driver has bugs
> > and
> > is only stable with !RO and Intel, then the driver shouldn't turn
> > it
> > on at all.
> >
> > In all of these cases it is not a user tunable.
> >
> > Development and testing reasons, like 'is my crash from a RO bug?'
> > to
> > tune should be met by the device global setpci, I think.
>
> +1
Be careful though to load driver with RO on and then setpci RO off..
not sure what the side effects are, unstable driver maybe ?
And not sure what should be the procedure then ? reload driver ? FW
will get a notification from PCI ?
next prev parent reply other threads:[~2020-07-10 2:18 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200623195229.26411-1-saeedm@mellanox.com>
[not found] ` <20200623195229.26411-11-saeedm@mellanox.com>
[not found] ` <20200623143118.51373eb7@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
[not found] ` <dda5c2b729bbaf025592aa84e2bdb84d0cda7570.camel@mellanox.com>
[not found] ` <082c6bfe-5146-c213-9220-65177717c342@mellanox.com>
2020-06-24 17:22 ` [net-next 10/10] net/mlx5e: Add support for PCI relaxed ordering Jakub Kicinski
2020-06-24 20:15 ` Saeed Mahameed
[not found] ` <20200624133018.5a4d238b@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
2020-07-06 13:00 ` Aya Levin
2020-07-06 16:52 ` Jakub Kicinski
2020-07-06 19:49 ` David Miller
2040-07-08 8:22 ` Aya Levin
2020-07-08 23:16 ` Bjorn Helgaas
2020-07-08 23:26 ` Jason Gunthorpe
2020-07-09 17:35 ` Jonathan Lemon
2020-07-09 18:20 ` Jason Gunthorpe
2020-07-09 19:47 ` Jakub Kicinski
2020-07-10 2:18 ` Saeed Mahameed [this message]
2020-07-10 12:21 ` Jason Gunthorpe
2020-07-09 20:33 ` Jonathan Lemon
2020-07-14 10:47 ` Aya Levin
2020-07-23 21:03 ` Alexander Duyck
2020-06-26 20:12 ` Bjorn Helgaas
2020-06-26 20:24 ` David Miller
2020-06-29 9:32 ` Aya Levin
2020-06-29 19:33 ` Bjorn Helgaas
2020-06-29 19:57 ` Raj, Ashok
2020-06-30 7:32 ` Ding Tianhong
2020-07-05 11:15 ` Aya Levin
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