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

[Dave Hansen]

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.