Re: [PATCH v3 1/3] x86/process: Shorten the default LAM tag width

[Maciej Wieczor-Retman]

On 2026-03-04 at 12:08:14 -0800, Dave Hansen wrote:
>On 3/2/26 07:34, Maciej Wieczor-Retman wrote:
>> With the announcement of ChkTag, it's worth preparing a stable x86
>> linear address masking (lam) user interface. One important aspect of lam
>> is the tag width, and aligning it with other industry solutions can
>> provide a more popular, generalized interface that other technologies
>> could utilize.
>> 
>> ChkTag will use 4-bit tags and since that's the direction other memory
>> tagging implementations seem to be taking too (for example Arm's MTE)
>> it's reasonable to converge lam in linux to the same specification. Even
>> though x86's LAM supports 6-bit tags it is beneficial to default lam to
>> 4 bits as ChkTag will likely be the main user of the interface and such
>> connection should simplify things in the future.
>
>The "default" naming in here doesn't make a whole lot of sense now that
>it's static.
>
>The changelog also needs a few things: first, it needs to talk about
>what this does to existing userspace. Second, it needs an imperative:
>
>	Shrink the maximum acceptable tag width from 6 to 4.
>
>But otherwise, this looks fine to me.

Thanks, I'll apply these things to the patchset.

-- 
Kind regards
Maciej Wieczór-Retman