Re: [PATCH 1/1] PCI: Fix Extend ACS configurability

Tushar Dave
2025-01-08T02:34:45Z

On 1/6/25 12:53, Bjorn Helgaas wrote:
> On Mon, Jan 06, 2025 at 12:34:00PM -0800, Tushar Dave wrote:
>> On 1/2/25 10:40, Jason Gunthorpe wrote:
>>> On Fri, Dec 13, 2024 at 12:29:42PM -0800, Tushar Dave wrote:
>>>
>>>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>>>> index dc663c0ca670..fc1c37910d1c 100644
>>>> --- a/Documentation/admin-guide/kernel-parameters.txt
>>>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>>>> @@ -4654,11 +4654,10 @@
>>>> Format:
>>>> <ACS flags>@<pci_dev>[; ...]
>>>> Specify one or more PCI devices (in the format
>>>> - specified above) optionally prepended with flags
>>>> - and separated by semicolons. The respective
>>>> - capabilities will be enabled, disabled or
>>>> - unchanged based on what is specified in
>>>> - flags.
>>>> + specified above) prepended with flags and separated
>>>> + by semicolons. The respective capabilities will be
>>>> + enabled, disabled or unchanged based on what is
>>>> + specified in flags.
>>>> ACS Flags is defined as follows:
>>>> bit-0 : ACS Source Validation
>>>> @@ -4673,7 +4672,7 @@
>>>> '1' – force enabled
>>>> 'x' – unchanged
>>>> For example,
>>>> - pci=config_acs=10x
>>>> + pci=config_acs=10x@pci:0:0
>>>> would configure all devices that support
>>>> ACS to enable P2P Request Redirect, disable
>>>> Translation Blocking, and leave Source
>>>
>>> Is this an unrelated change? The format of the command line shouldn't
>>> be changed to fix the described bug, why is the documentation changed?
>>
>> The documentation as it is (i.e. without my patch), is not correct.
>>
>> IOW, config_acs parameter does require flags and it is not optional. Without
>> flags it results into "ACS Flags missing". Therefore I remove word
>> "optionally" from the documentation text.
>>
>> Secondly, the syntax in the example 'pci=config_acs=10x' is incorrect. The
>> correct syntax should be 'pci=config_acs=10x@pci:0:0' that would configure
>> all devices that support ACS to enable P2P Request Redirect, disable
>> Translation Blocking, and leave Source Validation unchanged from whatever
>> power-up or firmware set it to.
>
> I'd suggest a separate patch to fix the documentation so we don't try
> to relate the doc changes with the code changes.

Sure thing. I will send a separate patch for the doc changes.

-Tushar