From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 2D98626E10; Mon, 16 Oct 2023 12:41:52 +0000 (UTC) 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 2BD30E8; Mon, 16 Oct 2023 05:41:50 -0700 (PDT) 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 589ACDA7; Mon, 16 Oct 2023 05:42:30 -0700 (PDT) Received: from monolith (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 547E43F5A1; Mon, 16 Oct 2023 05:41:44 -0700 (PDT) Date: Mon, 16 Oct 2023 13:42:17 +0100 From: Alexandru Elisei To: Hyesoo Yu 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, david@redhat.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 17/37] arm64: mte: Disable dynamic tag storage management if HW KASAN is enabled Message-ID: References: <20230823131350.114942-1-alexandru.elisei@arm.com> <20230823131350.114942-18-alexandru.elisei@arm.com> <20231012013505.GB2426387@tiffany> 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: <20231012013505.GB2426387@tiffany> X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Hi, On Thu, Oct 12, 2023 at 10:35:05AM +0900, Hyesoo Yu wrote: > On Wed, Aug 23, 2023 at 02:13:30PM +0100, Alexandru Elisei wrote: > > Reserving the tag storage associated with a tagged page requires the > > ability to migrate existing data if the tag storage is in use for data. > > > > The kernel allocates pages, which are now tagged because of HW KASAN, in > > non-preemptible contexts, which can make reserving the associate tag > > storage impossible. > > > > Don't expose the tag storage pages to the memory allocator if HW KASAN is > > enabled. > > > > Signed-off-by: Alexandru Elisei > > --- > > arch/arm64/kernel/mte_tag_storage.c | 12 ++++++++++++ > > 1 file changed, 12 insertions(+) > > > > diff --git a/arch/arm64/kernel/mte_tag_storage.c b/arch/arm64/kernel/mte_tag_storage.c > > index 4a6bfdf88458..f45128d0244e 100644 > > --- a/arch/arm64/kernel/mte_tag_storage.c > > +++ b/arch/arm64/kernel/mte_tag_storage.c > > @@ -314,6 +314,18 @@ static int __init mte_tag_storage_activate_regions(void) > > return 0; > > } > > > > + /* > > + * The kernel allocates memory in non-preemptible contexts, which makes > > + * migration impossible when reserving the associated tag storage. > > + * > > + * The check is safe to make because KASAN HW tags are enabled before > > + * the rest of the init functions are called, in smp_prepare_boot_cpu(). > > + */ > > + if (kasan_hw_tags_enabled()) { > > + pr_info("KASAN HW tags enabled, disabling tag storage"); > > + return 0; > > + } > > + > > Hi. > > Is there no plan to enable HW KASAN in the current design ? > I wonder if dynamic MTE is only used for user ? The tag storage pages are exposed to the page allocator if and only if HW KASAN is disabled: static int __init mte_tag_storage_activate_regions(void) [..] /* * The kernel allocates memory in non-preemptible contexts, which makes * migration impossible when reserving the associated tag storage. * * The check is safe to make because KASAN HW tags are enabled before * the rest of the init functions are called, in smp_prepare_boot_cpu(). */ if (kasan_hw_tags_enabled()) { pr_info("KASAN HW tags enabled, disabling tag storage"); return 0; } No plans at the moment to have this series compatible with HW KASAN. I will revisit this if/when the series gets merged. Thanks, Alex > > Thanks, > Hyesoo Yu. > > > > for (i = 0; i < num_tag_regions; i++) { > > tag_range = &tag_regions[i].tag_range; > > for (pfn = tag_range->start; pfn <= tag_range->end; pfn += pageblock_nr_pages) { > > -- > > 2.41.0 > > > >