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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 65936C433E0 for ; Thu, 4 Jun 2020 15:04:49 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 24D3D207D8 for ; Thu, 4 Jun 2020 15:04:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="sR5jTvHM" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 24D3D207D8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=pQT/UnTvqW92OdjOeqklekAshQNtXop09wTASisC4fI=; b=sR5jTvHMPvvm8y 4YcgUet0rBuXHO3SwOCzzBLIcfP1ocL2fEDs3b6P5nk5P0VD5O30PZhMg3JZsKaQ6nA4qDJa7XUCJ 5zqE7Hb+B9a2oMbyw6kAuq41TTcBOyvgyI+Oj4usloVu6BDKyJStn6uXYEQ1XtjAftHWyQJIvScfL +b+ydtfg6fBve9+fahxflFRW5iig9+GpeLFrIi8+2jy63GKHiyrAJRkVllt2w64OaCy6SH0QybBvu nG1MtZYAPmk/1JXJyOIod5NqNw6Wd9AMhHrP1wOz9tGHsHw+tiCF0c+s56pFb+DPErNAY0uxkU/lj KhQ7ALCvcKGC0VraUIJA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jgrQF-0004yh-L5; Thu, 04 Jun 2020 15:04:47 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jgrQC-0004y6-Ae for linux-arm-kernel@lists.infradead.org; Thu, 04 Jun 2020 15:04:45 +0000 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 A52571FB; Thu, 4 Jun 2020 08:04:41 -0700 (PDT) Received: from C02TD0UTHF1T.local (unknown [10.57.9.165]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2BA053F305; Thu, 4 Jun 2020 08:04:38 -0700 (PDT) Date: Thu, 4 Jun 2020 16:04:36 +0100 From: Mark Rutland To: Marc Zyngier Subject: Re: [PATCH 1/3] KVM: arm64: Save the host's PtrAuth keys in non-preemptible context Message-ID: <20200604150436.GC75320@C02TD0UTHF1T.local> References: <20200604133354.1279412-1-maz@kernel.org> <20200604133354.1279412-2-maz@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200604133354.1279412-2-maz@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200604_080444_452791_C73B653B X-CRM114-Status: GOOD ( 21.41 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kernel-team@android.com, kvm@vger.kernel.org, Suzuki K Poulose , Catalin Marinas , stable@vger.kernel.org, James Morse , Julien Thierry , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Jun 04, 2020 at 02:33:52PM +0100, Marc Zyngier wrote: > When using the PtrAuth feature in a guest, we need to save the host's > keys before allowing the guest to program them. For that, we dump > them in a per-CPU data structure (the so called host context). > > But both call sites that do this are in preemptible context, > which may end up in disaster should the vcpu thread get preempted > before reentering the guest. Yuck! > Instead, save the keys eagerly on each vcpu_load(). This has an > increased overhead, but is at least safe. > > Cc: stable@vger.kernel.org > Signed-off-by: Marc Zyngier This looks sound to me given kvm_arch_vcpu_load() is surrounded with get_cpu() .. put_cpu() and gets called when the thread is preempted. Reviewed-by: Mark Rutland Thanks, Mark. > --- > arch/arm64/include/asm/kvm_emulate.h | 6 ------ > arch/arm64/kvm/arm.c | 18 +++++++++++++++++- > arch/arm64/kvm/handle_exit.c | 19 ++----------------- > 3 files changed, 19 insertions(+), 24 deletions(-) > > diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h > index a30b4eec7cb4..977843e4d5fb 100644 > --- a/arch/arm64/include/asm/kvm_emulate.h > +++ b/arch/arm64/include/asm/kvm_emulate.h > @@ -112,12 +112,6 @@ static inline void vcpu_ptrauth_disable(struct kvm_vcpu *vcpu) > vcpu->arch.hcr_el2 &= ~(HCR_API | HCR_APK); > } > > -static inline void vcpu_ptrauth_setup_lazy(struct kvm_vcpu *vcpu) > -{ > - if (vcpu_has_ptrauth(vcpu)) > - vcpu_ptrauth_disable(vcpu); > -} > - > static inline unsigned long vcpu_get_vsesr(struct kvm_vcpu *vcpu) > { > return vcpu->arch.vsesr_el2; > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > index d6988401c22a..152049c5055d 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -337,6 +337,12 @@ void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu) > preempt_enable(); > } > > +#define __ptrauth_save_key(regs, key) \ > +({ \ > + regs[key ## KEYLO_EL1] = read_sysreg_s(SYS_ ## key ## KEYLO_EL1); \ > + regs[key ## KEYHI_EL1] = read_sysreg_s(SYS_ ## key ## KEYHI_EL1); \ > +}) > + > void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) > { > int *last_ran; > @@ -370,7 +376,17 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) > else > vcpu_set_wfx_traps(vcpu); > > - vcpu_ptrauth_setup_lazy(vcpu); > + if (vcpu_has_ptrauth(vcpu)) { > + struct kvm_cpu_context *ctxt = vcpu->arch.host_cpu_context; > + > + __ptrauth_save_key(ctxt->sys_regs, APIA); > + __ptrauth_save_key(ctxt->sys_regs, APIB); > + __ptrauth_save_key(ctxt->sys_regs, APDA); > + __ptrauth_save_key(ctxt->sys_regs, APDB); > + __ptrauth_save_key(ctxt->sys_regs, APGA); > + > + vcpu_ptrauth_disable(vcpu); > + } > } > > void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) > diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c > index eb194696ef62..065251efa2e6 100644 > --- a/arch/arm64/kvm/handle_exit.c > +++ b/arch/arm64/kvm/handle_exit.c > @@ -162,31 +162,16 @@ static int handle_sve(struct kvm_vcpu *vcpu, struct kvm_run *run) > return 1; > } > > -#define __ptrauth_save_key(regs, key) \ > -({ \ > - regs[key ## KEYLO_EL1] = read_sysreg_s(SYS_ ## key ## KEYLO_EL1); \ > - regs[key ## KEYHI_EL1] = read_sysreg_s(SYS_ ## key ## KEYHI_EL1); \ > -}) > - > /* > * Handle the guest trying to use a ptrauth instruction, or trying to access a > * ptrauth register. > */ > void kvm_arm_vcpu_ptrauth_trap(struct kvm_vcpu *vcpu) > { > - struct kvm_cpu_context *ctxt; > - > - if (vcpu_has_ptrauth(vcpu)) { > + if (vcpu_has_ptrauth(vcpu)) > vcpu_ptrauth_enable(vcpu); > - ctxt = vcpu->arch.host_cpu_context; > - __ptrauth_save_key(ctxt->sys_regs, APIA); > - __ptrauth_save_key(ctxt->sys_regs, APIB); > - __ptrauth_save_key(ctxt->sys_regs, APDA); > - __ptrauth_save_key(ctxt->sys_regs, APDB); > - __ptrauth_save_key(ctxt->sys_regs, APGA); > - } else { > + else > kvm_inject_undefined(vcpu); > - } > } > > /* > -- > 2.26.2 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel