From mboxrd@z Thu Jan 1 00:00:00 1970 From: Catalin Marinas Subject: [PATCH v4 24/26] arm64: mte: Introduce early param to disable MTE support Date: Fri, 15 May 2020 18:16:10 +0100 Message-ID: <20200515171612.1020-25-catalin.marinas@arm.com> References: <20200515171612.1020-1-catalin.marinas@arm.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: Received: from foss.arm.com ([217.140.110.172]:59618 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726231AbgEORRK (ORCPT ); Fri, 15 May 2020 13:17:10 -0400 In-Reply-To: <20200515171612.1020-1-catalin.marinas@arm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: linux-arm-kernel@lists.infradead.org Cc: linux-mm@kvack.org, linux-arch@vger.kernel.org, Will Deacon , Dave P Martin , Vincenzo Frascino , Szabolcs Nagy , Kevin Brodsky , Andrey Konovalov , Peter Collingbourne For performance analysis it may be desirable to disable MTE altogether via an early param. Introduce arm64.mte_disable and, if true, filter out the sanitised ID_AA64PFR1_EL1.MTE field to avoid exposing the HWCAP to user. Signed-off-by: Catalin Marinas Cc: Will Deacon --- Notes: New in v4. Documentation/admin-guide/kernel-parameters.txt | 4 ++++ arch/arm64/kernel/cpufeature.c | 11 +++++++++++ 2 files changed, 15 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index f2a93c8679e8..7436e7462b85 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -373,6 +373,10 @@ arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards Format: ,, + arm64.mte_disable= + [ARM64] Disable Linux support for the Memory + Tagging Extension (both user and in-kernel). + ataflop= [HW,M68k] atarimouse= [HW,MOUSE] Atari Mouse diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index aaadc1cbc006..f7596830694f 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -126,12 +126,23 @@ static void cpu_enable_cnp(struct arm64_cpu_capabilities const *cap); static bool __system_matches_cap(unsigned int n); #ifdef CONFIG_ARM64_MTE +static bool mte_disable; + +static int __init arm64_mte_disable(char *buf) +{ + return strtobool(buf, &mte_disable); +} +early_param("arm64.mte_disable", arm64_mte_disable); + s64 mte_ftr_filter(const struct arm64_ftr_bits *ftrp, s64 val) { struct device_node *np; static bool memory_checked = false; static bool mte_capable = true; + if (mte_disable) + return ID_AA64PFR1_MTE_NI; + /* EL0-only MTE is not supported by Linux, don't expose it */ if (val < ID_AA64PFR1_MTE) return ID_AA64PFR1_MTE_NI;