Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751374AbeAEKY3 (ORCPT + 1 other); Fri, 5 Jan 2018 05:24:29 -0500 Received: from foss.arm.com ([217.140.101.70]:42892 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751015AbeAEKY2 (ORCPT ); Fri, 5 Jan 2018 05:24:28 -0500 Subject: Re: [PATCH 03/11] arm64: Take into account ID_AA64PFR0_EL1.CSV3 To: Will Deacon , linux-arm-kernel@lists.infradead.org Cc: catalin.marinas@arm.com, ard.biesheuvel@linaro.org, marc.zyngier@arm.com, lorenzo.pieralisi@arm.com, christoffer.dall@linaro.org, linux-kernel@vger.kernel.org References: <1515078515-13723-1-git-send-email-will.deacon@arm.com> <1515078515-13723-4-git-send-email-will.deacon@arm.com> From: Suzuki K Poulose Message-ID: Date: Fri, 5 Jan 2018 10:24:25 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <1515078515-13723-4-git-send-email-will.deacon@arm.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On 04/01/18 15:08, Will Deacon wrote: > For non-KASLR kernels where the KPTI behaviour has not been overridden > on the command line we can use ID_AA64PFR0_EL1.CSV3 to determine whether > or not we should unmap the kernel whilst running at EL0. > > Signed-off-by: Will Deacon > --- > arch/arm64/include/asm/sysreg.h | 1 + > arch/arm64/kernel/cpufeature.c | 7 ++++++- > 2 files changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h > index 08cc88574659..ae519bbd3f9e 100644 > --- a/arch/arm64/include/asm/sysreg.h > +++ b/arch/arm64/include/asm/sysreg.h > @@ -437,6 +437,7 @@ > #define ID_AA64ISAR1_DPB_SHIFT 0 > > /* id_aa64pfr0 */ > +#define ID_AA64PFR0_CSV3_SHIFT 60 > #define ID_AA64PFR0_SVE_SHIFT 32 > #define ID_AA64PFR0_GIC_SHIFT 24 > #define ID_AA64PFR0_ASIMD_SHIFT 20 > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index 9f0545dfe497..e11c11bb5b02 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -145,6 +145,7 @@ static const struct arm64_ftr_bits ftr_id_aa64isar1[] = { > }; > > static const struct arm64_ftr_bits ftr_id_aa64pfr0[] = { > + ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_CSV3_SHIFT, 4, 0), > ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_SVE_SHIFT, 4, 0), > ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_GIC_SHIFT, 4, 0), > S_ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_ASIMD_SHIFT, 4, ID_AA64PFR0_ASIMD_NI), > @@ -851,6 +852,8 @@ static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */ > static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > int __unused) > { > + u64 pfr0 = read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1); > + > /* Forced on command line? */ > if (__kpti_forced) { > pr_info_once("kernel page table isolation forced %s by command line option\n", > @@ -862,7 +865,9 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) > return true; > > - return false; > + /* Defer to CPU feature registers */ > + return !cpuid_feature_extract_unsigned_field(pfr0, > + ID_AA64PFR0_CSV3_SHIFT); > } > The cpufeature bit changes look good to me. FWIW, Reviewed-by: Suzuki K Poulose