All of lore.kernel.org
 help / color / mirror / Atom feed
From: Catalin Marinas <catalin.marinas@arm.com>
To: Mark Brown <broonie@kernel.org>
Cc: Will Deacon <will@kernel.org>, Joey Gouly <joey.gouly@arm.com>,
	Branislav Rankov <branislav.rankov@arm.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v1 4/4] arm64/mte: Add userspace interface for enabling asymmetric mode
Date: Fri, 28 Jan 2022 17:15:14 +0000	[thread overview]
Message-ID: <YfQkotjUykKW93tb@arm.com> (raw)
In-Reply-To: <20220127195712.748150-5-broonie@kernel.org>

On Thu, Jan 27, 2022 at 07:57:12PM +0000, Mark Brown wrote:
> The architecture provides an asymmetric mode for MTE where tag mismatches
> are checked asynchronously for reads but synchronously for loads. Allow
> userspace processes to select this and make it available as a default mode
> via the existing per-CPU sysfs interface.
> 
> Since there PR_MTE_TCF_ values are a bitmask (allowing the kernel to choose
> between the multiple modes) and there are no free bits adjacent to the
> existing PR_MTE_TCF_ bits the set of bits used to specify the mode becomes
> disjoint. Programs using the new interface should be aware of this and
> programs that do not use it will not see any change in behaviour.
> 
> When userspace requests two possible modes but the system default for the
> CPU is the third mode (eg, default is synchronous but userspace requests
> either asynchronous or asymmetric) the preference order is:
> 
>    ASYMM > ASYNC > SYNC
> 
> This situation is not currently possible since there are only two modes and
> it is mandatory to have a system default so there could be no ambiguity and
> there is no ABI change. The chosen order is basically arbitrary as we do not
> have a clear metric for what is better here.
> 
> If userspace requests specifically asymmetric mode via the prctl() and the
> system does not support it then we will return an error, this mirrors
> how we handle the case where userspace enables MTE on a system that does
> not support MTE at all and the behaviour that will be seen if running on
> an older kernel that does not support userspace use of asymmetric mode.
> 
> Attempts to set asymmetric mode as the default mode will result in an error
> if the system does not support it.
> 
> Signed-off-by: Mark Brown <broonie@kernel.org>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  parent reply	other threads:[~2022-01-28 17:16 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-27 19:57 [PATCH v1 0/4] arm64/mte: Asymmetric MTE support in userspace Mark Brown
2022-01-27 19:57 ` [PATCH v1 1/4] arm64/mte: Document ABI for asymmetric mode Mark Brown
2022-01-28 16:43   ` Catalin Marinas
2022-01-28 17:23     ` Mark Brown
2022-01-28 16:55   ` Vincenzo Frascino
2022-02-15 18:14   ` Will Deacon
2022-02-16 16:36     ` Mark Brown
2022-02-16 17:06       ` Will Deacon
2022-01-27 19:57 ` [PATCH v1 2/4] arm64/mte: Add a little bit of documentation for mte_update_sctlr_user() Mark Brown
2022-01-28 16:45   ` Catalin Marinas
2022-01-28 16:57   ` Vincenzo Frascino
2022-01-27 19:57 ` [PATCH v1 3/4] arm64/mte: Add hwcap for asymmetric mode Mark Brown
2022-01-28 16:51   ` Catalin Marinas
2022-01-28 17:00   ` Vincenzo Frascino
2022-01-27 19:57 ` [PATCH v1 4/4] arm64/mte: Add userspace interface for enabling " Mark Brown
2022-01-28 17:12   ` Vincenzo Frascino
2022-01-28 17:15   ` Catalin Marinas [this message]
2022-03-02  0:52   ` Evgenii Stepanov
2022-03-02 11:44     ` Catalin Marinas
2022-03-02 13:10       ` Mark Brown
2022-03-02 18:44         ` Evgenii Stepanov
2022-03-02 19:33           ` Mark Brown
2022-03-02 20:58             ` Evgenii Stepanov
2022-03-03 10:34               ` Catalin Marinas
2022-03-03 15:44                 ` Mark Brown
2022-03-03 22:47                   ` Evgenii Stepanov
2022-03-04 21:09                 ` Peter Collingbourne
2022-03-07 15:36                   ` Catalin Marinas
2022-03-07 19:10                     ` Mark Brown
2022-03-07 20:55                       ` Peter Collingbourne
2022-03-08 13:34                         ` Mark Brown
2022-03-07 20:55                     ` Peter Collingbourne
2022-03-08 18:26                       ` Catalin Marinas
2022-02-10 21:43 ` [PATCH v1 0/4] arm64/mte: Asymmetric MTE support in userspace Branislav Rankov

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=YfQkotjUykKW93tb@arm.com \
    --to=catalin.marinas@arm.com \
    --cc=branislav.rankov@arm.com \
    --cc=broonie@kernel.org \
    --cc=joey.gouly@arm.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=will@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.