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

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Date:   Thu, 5 Aug 2021 21:14:50 +0800
From:   Dongdong Liu <liudongdong3@...wei.com>
To:     Logan Gunthorpe <logang@...tatee.com>, <helgaas@...nel.org>,
        <hch@...radead.org>, <kw@...ux.com>, <leon@...nel.org>,
        <linux-pci@...r.kernel.org>, <rajur@...lsio.com>,
        <hverkuil-cisco@...all.nl>
CC:     <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 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.

Thanks,
Dongdong
>
> Logan
> .
>