Re: [PATCH v10 13/13] x86/kasan: Make software tag-based kasan available

Dave Hansen
2026-02-26T23:29:16Z

On 2/24/26 01:10, Maciej Wieczor-Retman wrote:
>>> - ffdf000000000000 | -8.25 PB | fffffbffffffffff | ~8 PB | KASAN shadow memory
>>> + ffdf000000000000 | -8.25 PB | fffffbffffffffff | ~8 PB | KASAN shadow memory (generic mode)
>>> + ffeffc0000000000 | -6 PB | fffffbffffffffff | 4 PB | KASAN shadow memory (software tag-based mode)
>>> __________________|____________|__________________|_________|____________________________________________________________
>> I think the idea of these is that you can run through, find *one* range
>> and know what a given address maps to. This adds overlapping ranges.
>> Could you make it clear that part of the area is "generic mode" only and
>> the other part is for generic mode and for "software tag-based mode"?
> Boris suggested adding a footnote to clarify these are alternative ranges [1].
> Perhaps I can add a star '*' next to these two so it can notify someone to look for
> the footnote?
>
> [1] https://lore.kernel.org/
> all/20260113161047.GNaWZuh21aoxqtTNXS@fat_crate.local/

I'd rather this be:

ffdf000000000000 | -8.25 PB | fffffbffffffffff | ~8 PB | KASAN shadow memory[1]

...

1. talk about the ranges here. Maybe: Addresses <ffeffc0000000000 are used by
KASAN "generic mode" only. Addresses >=ffeffc0000000000 can additionally
be used by the software tag-based mode.

Or, list both ranges as separate:

ffdf000000000000 | -8.25 PB | ffeffbffffffffff | ~8 PB | KASAN shadow memory (generic mode only)
ffeffc0000000000 | -6 PB | fffffbffffffffff | 4 PB | KASAN shadow memory (generic or
software tag-based)
and describe the same use (generic mode) twice.