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

Maciej Wieczor-Retman
2026-02-27T08:27:51Z

On 2026-02-26 at 15:29:15 -0800, Dave Hansen wrote:
>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.

Thanks, I like the first option, I'll work on that.

--
Kind regards
Maciej Wieczór-Retman