From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201])
	(using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
	(No client certificate requested)
	by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7720179CC;
	Fri, 27 Oct 2023 11:04:42 +0000 (UTC)
Authentication-Results: smtp.subspace.kernel.org; dkim=none
Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0CAC0C433C8;
	Fri, 27 Oct 2023 11:04:35 +0000 (UTC)
Date: Fri, 27 Oct 2023 12:04:33 +0100
From: Catalin Marinas <catalin.marinas@arm.com>
To: Hyesoo Yu <hyesoo.yu@samsung.com>
Cc: Alexandru Elisei <alexandru.elisei@arm.com>,
	David Hildenbrand <david@redhat.com>, will@kernel.org,
	oliver.upton@linux.dev, maz@kernel.org, james.morse@arm.com,
	suzuki.poulose@arm.com, yuzenghui@huawei.com, arnd@arndb.de,
	akpm@linux-foundation.org, mingo@redhat.com, peterz@infradead.org,
	juri.lelli@redhat.com, vincent.guittot@linaro.org,
	dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com,
	mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com,
	mhiramat@kernel.org, rppt@kernel.org, hughd@google.com,
	pcc@google.com, steven.price@arm.com, anshuman.khandual@arm.com,
	vincenzo.frascino@arm.com, eugenis@google.com, kcc@google.com,
	linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
	kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org,
	linux-arch@vger.kernel.org, linux-mm@kvack.org,
	linux-trace-kernel@vger.kernel.org
Subject: Re: [PATCH RFC 00/37] Add support for arm64 MTE dynamic tag storage
 reuse
Message-ID: <ZTuZQYjcYFILtGYI@arm.com>
References: <0b9c122a-c05a-b3df-c69f-85f520294adc@redhat.com>
 <ZOd2LvUKMguWdlgq@arm.com>
 <ZPhfNVWXhabqnknK@monolith>
 <ZP7/e8YFiosElvTm@arm.com>
 <0cc8a118-2522-f666-5bcc-af06263fd352@redhat.com>
 <ZQHVVdlN9QQztc7Q@arm.com>
 <CGME20231025031004epcas2p485a0b7a9247bc61d54064d7f7bdd1e89@epcas2p4.samsung.com>
 <20231025025932.GA3953138@tiffany>
 <ZTjWKJ0K78jeCJr-@monolith>
 <20231025085258.GA1355131@tiffany>
Precedence: bulk
X-Mailing-List: linux-fsdevel@vger.kernel.org
List-Id: <linux-fsdevel.vger.kernel.org>
List-Subscribe: <mailto:linux-fsdevel+subscribe@vger.kernel.org>
List-Unsubscribe: <mailto:linux-fsdevel+unsubscribe@vger.kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20231025085258.GA1355131@tiffany>

On Wed, Oct 25, 2023 at 05:52:58PM +0900, Hyesoo Yu wrote:
> If we only avoid using ALLOC_CMA for __GFP_TAGGED, would we still be able to use
> the next iteration even if the hardware does not support "tag of tag" ? 

It depends on how the next iteration looks like. The plan was not to
support this so that we avoid another complication where a non-tagged
page is mprotect'ed to become tagged and it would need to be migrated
out of the CMA range. Not sure how much code it would save.

> I am not sure every vendor will support tag of tag, since there is no information
> related to that feature, like in the Google spec document.

If you are aware of any vendors not supporting this, please direct them
to the Arm support team, it would be very useful information for us.

Thanks.

-- 
Catalin