From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 789E1C433F5 for ; Mon, 21 Mar 2022 17:07:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351643AbiCURJM (ORCPT ); Mon, 21 Mar 2022 13:09:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51258 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346553AbiCURJL (ORCPT ); Mon, 21 Mar 2022 13:09:11 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 1B4E4AF1F1 for ; Mon, 21 Mar 2022 10:07:42 -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 B05001042; Mon, 21 Mar 2022 10:07:41 -0700 (PDT) Received: from monolith.localdoman (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id ACBA23F66F; Mon, 21 Mar 2022 10:07:39 -0700 (PDT) Date: Mon, 21 Mar 2022 17:08:14 +0000 From: Alexandru Elisei To: Vladimir Murzin Cc: will@kernel.org, kvm@vger.kernel.org, julien.thierry.kdev@gmail.com, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, steven.price@arm.com Subject: Re: [kvmtool PATCH 2/2] aarch64: Add support for MTE Message-ID: References: <20220321152820.246700-1-alexandru.elisei@arm.com> <20220321152820.246700-3-alexandru.elisei@arm.com> <3cf3b621-5a07-5c06-cb9f-f9c776b6717d@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3cf3b621-5a07-5c06-cb9f-f9c776b6717d@arm.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hi, On Mon, Mar 21, 2022 at 03:40:18PM +0000, Vladimir Murzin wrote: > Hi Alexandru, > > On 3/21/22 3:28 PM, Alexandru Elisei wrote: > > MTE has been supported in Linux since commit 673638f434ee ("KVM: arm64: > > Expose KVM_ARM_CAP_MTE"), add support for it in kvmtool. > > > > Signed-off-by: Alexandru Elisei > > --- > > arm/aarch32/include/kvm/kvm-arch.h | 3 +++ > > arm/aarch64/include/kvm/kvm-arch.h | 1 + > > arm/aarch64/include/kvm/kvm-config-arch.h | 2 ++ > > arm/aarch64/kvm.c | 13 +++++++++++++ > > arm/include/arm-common/kvm-config-arch.h | 1 + > > arm/kvm.c | 3 +++ > > 6 files changed, 23 insertions(+) > > > > diff --git a/arm/aarch32/include/kvm/kvm-arch.h b/arm/aarch32/include/kvm/kvm-arch.h > > index bee2fc255a82..5616b27e257e 100644 > > --- a/arm/aarch32/include/kvm/kvm-arch.h > > +++ b/arm/aarch32/include/kvm/kvm-arch.h > > @@ -5,6 +5,9 @@ > > > > #define kvm__arch_get_kern_offset(...) 0x8000 > > > > +struct kvm; > > +static inline void kvm__arch_enable_mte(struct kvm *kvm) {} > > + > > #define ARM_MAX_MEMORY(...) ARM_LOMAP_MAX_MEMORY > > > > #define MAX_PAGE_SIZE SZ_4K > > diff --git a/arm/aarch64/include/kvm/kvm-arch.h b/arm/aarch64/include/kvm/kvm-arch.h > > index 5e5ee41211ed..9124f6919d0f 100644 > > --- a/arm/aarch64/include/kvm/kvm-arch.h > > +++ b/arm/aarch64/include/kvm/kvm-arch.h > > @@ -6,6 +6,7 @@ > > struct kvm; > > unsigned long long kvm__arch_get_kern_offset(struct kvm *kvm, int fd); > > int kvm__arch_get_ipa_limit(struct kvm *kvm); > > +void kvm__arch_enable_mte(struct kvm *kvm); > > > > #define ARM_MAX_MEMORY(kvm) ({ \ > > u64 max_ram; \ > > diff --git a/arm/aarch64/include/kvm/kvm-config-arch.h b/arm/aarch64/include/kvm/kvm-config-arch.h > > index 04be43dfa9b2..11250365d8d5 100644 > > --- a/arm/aarch64/include/kvm/kvm-config-arch.h > > +++ b/arm/aarch64/include/kvm/kvm-config-arch.h > > @@ -6,6 +6,8 @@ > > "Run AArch32 guest"), \ > > OPT_BOOLEAN('\0', "pmu", &(cfg)->has_pmuv3, \ > > "Create PMUv3 device"), \ > > + OPT_BOOLEAN('\0', "mte", &(cfg)->has_mte, \ > > + "Enable memory tagging extension"), \ > > OPT_U64('\0', "kaslr-seed", &(cfg)->kaslr_seed, \ > > "Specify random seed for Kernel Address Space " \ > > "Layout Randomization (KASLR)"), > > diff --git a/arm/aarch64/kvm.c b/arm/aarch64/kvm.c > > index 56a0aedc263d..46548f8ee96e 100644 > > --- a/arm/aarch64/kvm.c > > +++ b/arm/aarch64/kvm.c > > @@ -81,3 +81,16 @@ int kvm__get_vm_type(struct kvm *kvm) > > > > return KVM_VM_TYPE_ARM_IPA_SIZE(ipa_bits); > > } > > + > > +void kvm__arch_enable_mte(struct kvm *kvm) > > +{ > > + struct kvm_enable_cap cap = { > > + .cap = KVM_CAP_ARM_MTE, > > + }; > > + > > + if (!kvm__supports_extension(kvm, KVM_CAP_ARM_MTE)) > > + die("MTE capability is not supported"); > > + > > + if (ioctl(kvm->vm_fd, KVM_ENABLE_CAP, &cap)) > > + die_perror("KVM_ENABLE_CAP(KVM_CAP_ARM_MTE)"); > > +} > > diff --git a/arm/include/arm-common/kvm-config-arch.h b/arm/include/arm-common/kvm-config-arch.h > > index 5734c46ab9e6..16e8d500a71b 100644 > > --- a/arm/include/arm-common/kvm-config-arch.h > > +++ b/arm/include/arm-common/kvm-config-arch.h > > @@ -9,6 +9,7 @@ struct kvm_config_arch { > > bool virtio_trans_pci; > > bool aarch32_guest; > > bool has_pmuv3; > > + bool has_mte; > > u64 kaslr_seed; > > enum irqchip_type irqchip; > > u64 fw_addr; > > diff --git a/arm/kvm.c b/arm/kvm.c > > index 80d233f13d0b..f2db93953778 100644 > > --- a/arm/kvm.c > > +++ b/arm/kvm.c > > @@ -86,6 +86,9 @@ void kvm__arch_init(struct kvm *kvm, const char *hugetlbfs_path, u64 ram_size) > > /* Create the virtual GIC. */ > > if (gic__create(kvm, kvm->cfg.arch.irqchip)) > > die("Failed to create virtual GIC"); > > + > > + if (kvm->cfg.arch.has_mte) > > + kvm__arch_enable_mte(kvm); > > } > > Can we enable it unconditionally if KVM_CAP_ARM_MTE is supported like we do for > PAC and SVE? I thought about that, the reason I chose to enable it based a kvmtool command line option, instead of always being enabled if available, is because of the overhead of sanitising the MTE tags on each stage 2 data abort. Steven, am I overreacting and that overhead is negligible? Also, as far as I know, PAC and SVE incur basically no overhead in KVM until the guest starts to use those features. Do you have a specific reason for wanting MTE to always be enabled if available? I'm happy to be convinced to make MTE enabled by default, I don't have preference either way. Thanks, Alex