linux-kernel - Re: [PATCH net-next] eth: fbnic: Add PCIe hardware statistics

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Message-ID: <20241106211738.GA1540450@bhelgaas>
Date: Wed, 6 Nov 2024 15:17:38 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Leon Romanovsky <leon@...nel.org>
Cc: Sanman Pradhan <sanman.p211993@...il.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, netdev@...r.kernel.org,
	alexanderduyck@...com, kuba@...nel.org, kernel-team@...a.com,
	davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com,
	horms@...nel.org, corbet@....net, mohsin.bashr@...il.com,
	sanmanpradhan@...a.com, andrew+netdev@...n.ch,
	vadim.fedorenko@...ux.dev, jdamato@...tly.com, sdf@...ichev.me,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH net-next] eth: fbnic: Add PCIe hardware statistics

On Wed, Nov 06, 2024 at 07:50:54PM +0200, Leon Romanovsky wrote:
> On Wed, Nov 06, 2024 at 11:12:57AM -0600, Bjorn Helgaas wrote:
> > On Wed, Nov 06, 2024 at 02:22:51PM +0200, Leon Romanovsky wrote:
> > > On Tue, Nov 05, 2024 at 04:26:25PM -0800, Sanman Pradhan wrote:
> > > > Add PCIe hardware statistics support to the fbnic driver. These stats
> > > > provide insight into PCIe transaction performance and error conditions,
> > > > including, read/write and completion TLP counts and DWORD counts and
> > > > debug counters for tag, completion credit and NP credit exhaustion
> > > > 
> > > > The stats are exposed via ethtool and can be used to monitor PCIe
> > > > performance and debug PCIe issues.
> > > 
> > > And how does PCIe statistics belong to ethtool?
> > > 
> > > This PCIe statistics to debug PCIe errors and arguably should be part of
> > > PCI core and not hidden in netdev tool.
> > 
> > How would this be done in the PCI core?  As far as I can tell, all
> > these registers are device-specific and live in some device BAR.
> 
> I would expect some sysfs file/directory exposed through PCI core.
> That sysfs needs to be connected to the relevant device through
> callback, like we are doing with .sriov_configure(). So every PCI
> device will be able to expose statistics without relation to netdev.
> 
> That interface should provide read access and write access with zero
> value to reset the counter/counters.

Seems plausible.  We do already have something sort of similar with
aer_stats_attrs[].  I don't think there's a way to reset them though,
and they're just all thrown in the top-level device directory, which
probably isn't scalable.

Bjorn