netdev - Re: [PATCH V7 7/9] PCI/sysfs: Add a 10-Bit Tag sysfs file

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Message-ID: <YQvtcjudPQQ8LToU@unreal>
Date:   Thu, 5 Aug 2021 16:53:54 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Dongdong Liu <liudongdong3@...wei.com>
Cc:     Logan Gunthorpe <logang@...tatee.com>, helgaas@...nel.org,
        hch@...radead.org, kw@...ux.com, linux-pci@...r.kernel.org,
        rajur@...lsio.com, hverkuil-cisco@...all.nl,
        linux-media@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH V7 7/9] PCI/sysfs: Add a 10-Bit Tag sysfs file

On Thu, Aug 05, 2021 at 09:14:50PM +0800, Dongdong Liu wrote:
> On 2021/8/4 23:51, Logan Gunthorpe wrote:
> > 
> > 
> > 
> > On 2021-08-04 7:47 a.m., Dongdong Liu wrote:
> > > PCIe spec 5.0 r1.0 section 2.2.6.2 says that if an Endpoint supports
> > > sending Requests to other Endpoints (as opposed to host memory), the
> > > Endpoint must not send 10-Bit Tag Requests to another given Endpoint
> > > unless an implementation-specific mechanism determines that the Endpoint
> > > supports 10-Bit Tag Completer capability. Add a 10bit_tag sysfs file,
> > > write 0 to disable 10-Bit Tag Requester when the driver does not bind
> > > the device if the peer device does not support the 10-Bit Tag Completer.
> > > This will make P2P traffic safe. the 10bit_tag file content indicate
> > > current 10-Bit Tag Requester Enable status.
> > 
> > Can we not have both the sysfs file and the command line parameter? If
> > the user wants to disable it always for a specific device this sysfs
> > parameter is fairly awkward. A script at boot to unbind the driver, set
> > the sysfs file and rebind the driver is not trivial and the command line
> > parameter offers additional options for users.
> Does the command line parameter as "[PATCH V6 7/8] PCI: Add
> "pci=disable_10bit_tag=" parameter for peer-to-peer support" does?
> 
> Do we also need such command line if we already had sysfs file?
> I think we may not need.

I think the same.

> 
> Thanks,
> Dongdong
> > 
> > Logan
> > .
> >