Re: [RFC PATCH 0/2] kasan: hw_tags: Add option to tag only at allocation time

[Catalin Marinas <catalin.marinas@arm.com>]

On Thu, Jun 18, 2026 at 11:05:43PM +0900, Harry Yoo wrote:
> On 6/18/26 10:35 PM, Harry Yoo wrote:
> > On 6/12/26 1:44 PM, Dev Jain wrote:
> >> Introduce a boot option to tag only at allocation time of the objects. This
> >> reduces KASAN MTE overhead, the tradeoff being reduced ability of
> >> catching bugs.
> > 
> > I think most of overhead when enabling MTE comes from loading and
> > validing tags for every memory access (either in SYNC or ASYNC mode),
> > rather than from storing tags.
> 
> Is there any reason not to use STGM instead of STG + DC GVA when
> setting/clearing tags for large sizes when we know they are properly
> aligned?

STGM is intended for copying tags when paired with LDGM. Have you seen
hardware where STGM is faster than STG or DC GVA? For properly aligned
buffers, I'd expect DC GVA to behave at least on par with STGM.

-- 
Catalin