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

Logan Gunthorpe
2021-08-05T15:37:06Z

On 2021-08-05 7:14 a.m., 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.

In my opinion, for reasons stated above, the command line parameter is
way more convenient.

Logan