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 X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0BED5C43381 for ; Tue, 26 Mar 2019 04:04:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D9FFE20828 for ; Tue, 26 Mar 2019 04:04:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726413AbfCZEEF (ORCPT ); Tue, 26 Mar 2019 00:04:05 -0400 Received: from foss.arm.com ([217.140.101.70]:58914 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726302AbfCZEEF (ORCPT ); Tue, 26 Mar 2019 00:04:05 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9DC8880D; Mon, 25 Mar 2019 21:04:04 -0700 (PDT) Received: from [10.162.0.144] (a075553-lin.blr.arm.com [10.162.0.144]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DA45A3F59C; Mon, 25 Mar 2019 21:04:00 -0700 (PDT) Subject: Re: [PATCH v7 7/10] KVM: arm/arm64: context-switch ptrauth registers To: Kristina Martsenko , linux-arm-kernel@lists.infradead.org Cc: Christoffer Dall , Marc Zyngier , Catalin Marinas , Will Deacon , Andrew Jones , Dave Martin , Ramana Radhakrishnan , kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, Mark Rutland , James Morse , Julien Thierry References: <1552984243-7689-1-git-send-email-amit.kachhap@arm.com> <1552984243-7689-8-git-send-email-amit.kachhap@arm.com> <64505666-8a1f-cf64-7067-4b2dd53b0b40@arm.com> From: Amit Daniel Kachhap Message-ID: Date: Tue, 26 Mar 2019 09:33:58 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <64505666-8a1f-cf64-7067-4b2dd53b0b40@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 3/26/19 1:34 AM, Kristina Martsenko wrote: > On 19/03/2019 08:30, Amit Daniel Kachhap wrote: >> From: Mark Rutland >> >> When pointer authentication is supported, a guest may wish to use it. >> This patch adds the necessary KVM infrastructure for this to work, with >> a semi-lazy context switch of the pointer auth state. >> >> Pointer authentication feature is only enabled when VHE is built >> in the kernel and present in the CPU implementation so only VHE code >> paths are modified. >> >> When we schedule a vcpu, we disable guest usage of pointer >> authentication instructions and accesses to the keys. While these are >> disabled, we avoid context-switching the keys. When we trap the guest >> trying to use pointer authentication functionality, we change to eagerly >> context-switching the keys, and enable the feature. The next time the >> vcpu is scheduled out/in, we start again. However the host key save is >> optimized and implemented inside ptrauth instruction/register access >> trap. >> >> Pointer authentication consists of address authentication and generic >> authentication, and CPUs in a system might have varied support for >> either. Where support for either feature is not uniform, it is hidden >> from guests via ID register emulation, as a result of the cpufeature >> framework in the host. >> >> Unfortunately, address authentication and generic authentication cannot >> be trapped separately, as the architecture provides a single EL2 trap >> covering both. If we wish to expose one without the other, we cannot >> prevent a (badly-written) guest from intermittently using a feature >> which is not uniformly supported (when scheduled on a physical CPU which >> supports the relevant feature). Hence, this patch expects both type of >> authentication to be present in a cpu. >> >> This switch of key is done from guest enter/exit assembly as preperation >> for the upcoming in-kernel pointer authentication support. Hence, these >> key switching routines are not implemented in C code as they may cause >> pointer authentication key signing error in some situations. >> >> Signed-off-by: Mark Rutland >> [Only VHE, key switch in full assembly, vcpu_has_ptrauth checks >> , save host key in ptrauth exception trap] >> Signed-off-by: Amit Daniel Kachhap >> Reviewed-by: Julien Thierry >> Cc: Marc Zyngier >> Cc: Christoffer Dall >> Cc: kvmarm@lists.cs.columbia.edu > > [...] > >> +/* SPDX-License-Identifier: GPL-2.0 >> + * arch/arm64/include/asm/kvm_ptrauth_asm.h: Guest/host ptrauth save/restore >> + * Copyright 2019 Arm Limited >> + * Author: Mark Rutland >> + * Amit Daniel Kachhap >> + */ > > I think the license needs to be in its own comment, like > > /* SPDX-License-Identifier: GPL-2.0 */ yes this is indeed the format followed. > /* arch/arm64/include/asm/kvm_ptrauth_asm.h: ... > * ... > */ > >> + >> +#ifndef __ASM_KVM_ASM_PTRAUTH_H >> +#define __ASM_KVM_ASM_PTRAUTH_H > > __ASM_KVM_PTRAUTH_ASM_H ? (to match the file name) > >> + if (test_bit(KVM_ARM_VCPU_PTRAUTH_ADDRESS, vcpu->arch.features) || >> + test_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, vcpu->arch.features)) { >> + /* Verify that KVM startup matches the conditions for ptrauth */ >> + if (WARN_ON(!vcpu_has_ptrauth(vcpu))) >> + return -EINVAL; >> + } > > I think this now needs to have "goto out;" instead of "return -EINVAL;", > since 5.1-rcX contains commit e761a927bc9a ("KVM: arm/arm64: Reset the > VCPU without preemption and vcpu state loaded") which changed some of > this code. ok missed the changes for this commit. > >> @@ -385,6 +385,8 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) >> vcpu_clear_wfe_traps(vcpu); >> else >> vcpu_set_wfe_traps(vcpu); >> + >> + kvm_arm_vcpu_ptrauth_setup_lazy(vcpu); > > This version of the series seems to have lost the arch/arm/ definition > of kvm_arm_vcpu_ptrauth_setup_lazy (previously > kvm_arm_vcpu_ptrauth_reset), so KVM no longer compiles for arch/arm/ :( ok my bad. Thanks, Amit D > > Thanks, > Kristina >