From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladimir Murzin Subject: [PATCH v2 3/3] arm64: Introduce command line parameter to disable CNP Date: Wed, 11 Oct 2017 13:19:55 +0100 Message-ID: <1507724395-13735-4-git-send-email-vladimir.murzin@arm.com> References: <1507724395-13735-1-git-send-email-vladimir.murzin@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 3450C49D39 for ; Wed, 11 Oct 2017 08:19:36 -0400 (EDT) Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 8ZcM+7exSY4v for ; Wed, 11 Oct 2017 08:19:34 -0400 (EDT) Received: from foss.arm.com (foss.arm.com [217.140.101.70]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 7322C49D6F for ; Wed, 11 Oct 2017 08:19:34 -0400 (EDT) In-Reply-To: <1507724395-13735-1-git-send-email-vladimir.murzin@arm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu To: linux-arm-kernel@lists.infradead.org Cc: marc.zyngier@arm.com, catalin.marinas@arm.com, kbuild-all@01.org, kvmarm@lists.cs.columbia.edu List-Id: kvmarm@lists.cs.columbia.edu There are cases when activating of Common Not Private (CNP) feature might not be desirable; this patch allows to forcefully disable CNP even it is supported by hardware. Signed-off-by: Vladimir Murzin --- Documentation/admin-guide/kernel-parameters.txt | 4 ++++ arch/arm64/kernel/cpufeature.c | 16 +++++++++++++++- 2 files changed, 19 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 0549662..3c1e45d 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2560,6 +2560,10 @@ noclflush [BUGS=X86] Don't use the CLFLUSH instruction + nocnp [ARM64] + Disable CNP (Common not Private translations) + even if it is supported by processor. + nodelayacct [KNL] Disable per-task delay accounting nodsp [SH] Disable hardware DSP at boot time. diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 83809a8..9bceca3 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -771,6 +771,20 @@ static bool has_no_hw_prefetch(const struct arm64_cpu_capabilities *entry, int _ MIDR_CPU_VAR_REV(1, MIDR_REVISION_MASK)); } +static bool nocnp; + +static int __init early_nocnp(char *p) +{ + nocnp = true; + return 0; +} +early_param("nocnp", early_nocnp); + +static bool has_useable_cnp(const struct arm64_cpu_capabilities *entry, int scope) +{ + return has_cpuid_feature(entry, scope) && !nocmp; +} + static bool runs_at_el2(const struct arm64_cpu_capabilities *entry, int __unused) { return is_kernel_in_hyp_mode(); @@ -905,7 +919,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = { .desc = "Common not Private translations", .capability = ARM64_HAS_CNP, .def_scope = SCOPE_SYSTEM, - .matches = has_cpuid_feature, + .matches = has_useable_cnp, .sys_reg = SYS_ID_AA64MMFR2_EL1, .sign = FTR_UNSIGNED, .field_pos = ID_AA64MMFR2_CNP_SHIFT, -- 2.0.0