linux-kernel - Re: [PATCH 2/2] arm64: mte: Defer disabling of TCO until user_access

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Message-ID: <87bjiw9byg.fsf@rasp.cworth.amperemail.amperecomputing.com>
Date: Wed, 14 Jan 2026 12:27:35 -0800
From: Carl Worth <carl@...amperecomputing.com>
To: Catalin Marinas <catalin.marinas@....com>, Taehyun Noh <taehyun@...xas.edu>
Cc: Will Deacon <will@...nel.org>, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, andreyknvl@...il.com, pcc@...gle.com,
 yeoreum.yun@....com
Subject: Re: [PATCH 2/2] arm64: mte: Defer disabling of TCO until
 user_access_begin/end

Catalin Marinas <catalin.marinas@....com> writes:
> On Fri, Jan 09, 2026 at 11:29:29PM -0600, Taehyun Noh wrote:
>> Our team agrees with Catalin’s TCMA1 solution. It disables every kernel
>> tag checking but the user address will get tag checked as far as TCO is
>> clear. Also, Carl’s initial testing confirms that
>> `mem_access_checked*:k` counters drop with the TCMA1 patch. While we
>> haven’t run the memcached benchmark yet, we will follow up with those
>> results shortly.
>
> That's great. Carl, could you please respin the patch with just setting
> the TCMA1 bit? Just add a suggested-by me (I could post the patch as
> well but I don't have the data to back it up and include in the commit
> log).

Will do. I'm just running the final benchmark numbers and then will send
this out.

-Carl