From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=none Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 7074710EB; Tue, 28 Nov 2023 09:18:07 -0800 (PST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9871BC15; Tue, 28 Nov 2023 09:18:54 -0800 (PST) Received: from raptor (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4C82A3F6C4; Tue, 28 Nov 2023 09:18:02 -0800 (PST) Date: Tue, 28 Nov 2023 17:17:59 +0000 From: Alexandru Elisei To: David Hildenbrand Cc: catalin.marinas@arm.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, hyesoo.yu@samsung.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 v2 06/27] mm: page_alloc: Allow an arch to hook early into free_pages_prepare() Message-ID: References: <20231119165721.9849-1-alexandru.elisei@arm.com> <20231119165721.9849-7-alexandru.elisei@arm.com> <45466b05-d620-41e5-8a2b-05c420b8fa7b@redhat.com> <2e2d3f51-34e3-4982-b982-ab7b555cba21@redhat.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2e2d3f51-34e3-4982-b982-ab7b555cba21@redhat.com> Hi, On Tue, Nov 28, 2023 at 05:58:55PM +0100, David Hildenbrand wrote: > On 27.11.23 14:03, Alexandru Elisei wrote: > > Hi, > > > > On Fri, Nov 24, 2023 at 08:36:52PM +0100, David Hildenbrand wrote: > > > On 19.11.23 17:57, Alexandru Elisei wrote: > > > > Add arch_free_pages_prepare() hook that is called before that page flags > > > > are cleared. This will be used by arm64 when explicit management of tag > > > > storage pages is enabled. > > > > > > Can you elaborate a bit what exactly will be done by that code with that > > > information? > > > > Of course. > > > > The MTE code that is in the kernel today uses the PG_arch_2 page flag, which it > > renames to PG_mte_tagged, to track if a page has been mapped with tagging > > enabled. That flag is cleared by free_pages_prepare() when it does: > > > > page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; > > > > When tag storage management is enabled, tag storage is reserved for a page if > > and only if the page is mapped as tagged. When a page is freed, the code looks > > at the PG_mte_tagged flag to determine if the page was mapped as tagged, and > > therefore has tag storage reserved, to determine if the corresponding tag > > storage should also be freed. > > > > I have considered using arch_free_page(), but free_pages_prepare() calls the > > function after the flags are cleared. > > > > Does that answer your question? > > Yes, please add some of that to the patch description! Will do! Thanks, Alex > > -- > Cheers, > > David / dhildenb >