Re: 答复: [外部邮件] Re: [PATCH] docs: kernel-parameters: fix architecture alignment for pt, nopt, and nobypass

[Randy Dunlap]

On 3/29/26 8:08 PM, Li,Rongqing(ACG CCN) wrote:
> 
> 
>> -----邮件原件-----
>> 发件人: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
>> 发送时间: 2026年3月27日 0:08
>> 收件人: Li,Rongqing(ACG CCN) <lirongqing@xxxxxxxxx>; Jonathan Corbet
>> <corbet@xxxxxxx>; Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>; Andrew Morton
>> <akpm@xxxxxxxxxxxxxxxxxxxx>; Borislav Petkov <bp@xxxxxxxxx>; Peter Zijlstra
>> <peterz@xxxxxxxxxxxxx>; Feng Tang <feng.tang@xxxxxxxxxxxxxxxxx>; Pawan
>> Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>; Dapeng Mi
>> <dapeng1.mi@xxxxxxxxxxxxxxx>; Kees Cook <kees@xxxxxxxxxx>; Marco Elver
>> <elver@xxxxxxxxxx>; Paul E . McKenney <paulmck@xxxxxxxxxx>; Askar Safin
>> <safinaskar@xxxxxxxxx>; Bjorn Helgaas <bhelgaas@xxxxxxxxxx>; Sohil Mehta
>> <sohil.mehta@xxxxxxxxx>; linux-doc@xxxxxxxxxxxxxxx;
>> linux-kernel@xxxxxxxxxxxxxxx
>> 主题: [外部邮件] Re: [PATCH] docs: kernel-parameters: fix architecture
>> alignment for pt, nopt, and nobypass
>>
>> Hi,
>>
>> On 3/26/26 12:46 AM, lirongqing wrote:
>>> From: Li RongQing <lirongqing@xxxxxxxxx>
>>>
>>> Commit ab0e7f20768a ("Documentation: Merge x86-specific boot options
>>> doc into kernel-parameters.txt") introduced a formatting regression
>>> where architecture tags were placed on separate lines with broken
>> indentation.
>>> This caused the 'nopt' [X86] parameter to appear as if it belonged to
>>> the [PPC/POWERNV] section.
>>>
>>> Fix the formatting by placing the architecture tags on the same line
>>> as their respective parameters ('pt', 'nopt', and 'nobypass') and
>>> restoring proper indentation.
>>>
>>> Fixes: ab0e7f20768a ("Documentation: Merge x86-specific boot options
>>> doc into kernel-parameters.txt")
>>> Signed-off-by: Li RongQing <lirongqing@xxxxxxxxx>
>>> ---
>>>  Documentation/admin-guide/kernel-parameters.txt | 9 +++------
>>>  1 file changed, 3 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/Documentation/admin-guide/kernel-parameters.txt
>>> b/Documentation/admin-guide/kernel-parameters.txt
>>> index 03a5506..dc1c5bd 100644
>>> --- a/Documentation/admin-guide/kernel-parameters.txt
>>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>>> @@ -2615,12 +2615,9 @@ Kernel parameters
>>>  			Intel machines). This can be used to prevent the usage
>>>  			of an available hardware IOMMU.
>>>
>>> -			[X86]
>>> -		pt
>>> -			[X86]
>>> -		nopt
>>> -			[PPC/POWERNV]
>>> -		nobypass
>>> +		pt  	[X86]
>>> +		nopt	[X86]
>>> +		nobypass	[PPC/POWERNV]
>>>  			Disable IOMMU bypass, using IOMMU for PCI devices.
>>>
>>>  		[X86]
>>
>> This looks good as far as it goes, but there are still some problems IMO.
>>
>> These are all iommu= options, but iommu says that it's for [X86,EARLY].
>> No PPC/POWERNV mentioned there.
> 
> I think [PPC/POWERNV] should not be added to the main iommu= header. Since that header is already tagged as [X86, EARLY], adding PowerPC there would imply all subsequent options are cross-platform. Instead, it is cleaner to keep the main header as X86-specific and explicitly tag the individual nobypass option for [PPC/POWERNV]. This avoids the need to redundantly label every other X86-only option (like pt or nopt) within the section.
> 
>>
>> Then immediately following nobypass, there is this:
>> 		[X86]
>> 		AMD Gart HW IOMMU-specific options:
>>
>> which is also in questionable format. The [X86] isn't needed at all IMO, or if it's
>> desirable, those 2 lines should be on one line.
>>
> You are right , [X86] isn't needed , How about to remove the [X86], like below 
> 
>     Documentation/kernel-parameters: fix architecture alignment for pt, nopt, and nobypass
> 
>     Commit ab0e7f20768a ("Documentation: Merge x86-specific boot options doc
>     into kernel-parameters.txt") introduced a formatting regression where
>     architecture tags were placed on separate lines with broken indentation.
>     This caused the 'nopt' [X86] parameter to appear as if it belonged to
>     the [PPC/POWERNV] section.
> 
>     Furthermore, since the main 'iommu=' parameter heading already specifies
>     it is for [X86, EARLY], the subsequent standalone [X86] tags for 'pt',
>     'nopt', and the AMD GART options are redundant and clutter the
>     documentation.
> 
>     Clean up the formatting by removing these redundant tags and properly
>     attributing the 'nobypass' option to [PPC/POWERNV].
> 
>     Fixes: ab0e7f20768a ("Documentation: Merge x86-specific boot options doc into kernel-parameters.txt")
>     Signed-off-by: Li RongQing <lirongqing@xxxxxxxxx>
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 03a5506..5253c23 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2615,15 +2615,11 @@ Kernel parameters
>                         Intel machines). This can be used to prevent the usage
>                         of an available hardware IOMMU.
> 
> -                       [X86]
>                 pt
> -                       [X86]
>                 nopt
> -                       [PPC/POWERNV]
> -               nobypass
> +               nobypass        [PPC/POWERNV]
>                         Disable IOMMU bypass, using IOMMU for PCI devices.
> 
> -               [X86]
>                 AMD Gart HW IOMMU-specific options:
> 
>                 <size>
> [Li,Rongqing] 
> 

Yes, LGTM. Thanks.

Acked-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>


-- 
~Randy