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=-14.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,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 F0261C433DB for ; Tue, 29 Dec 2020 17:17:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C1182221F8 for ; Tue, 29 Dec 2020 17:17:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726420AbgL2RRZ (ORCPT ); Tue, 29 Dec 2020 12:17:25 -0500 Received: from mail.kernel.org ([198.145.29.99]:45404 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726258AbgL2RRY (ORCPT ); Tue, 29 Dec 2020 12:17:24 -0500 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CC47A21D94; Tue, 29 Dec 2020 17:16:43 +0000 (UTC) Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94) (envelope-from ) id 1kuIbx-004Ri2-Kb; Tue, 29 Dec 2020 17:16:41 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Tue, 29 Dec 2020 17:16:41 +0000 From: Marc Zyngier To: David Brazdil Cc: kvmarm@lists.cs.columbia.edu, James Morse , Julien Thierry , Suzuki K Poulose , Catalin Marinas , Will Deacon , Mark Rutland , Lorenzo Pieralisi , Sudeep Holla , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH] KVM: arm64: Allow PSCI SYSTEM_OFF/RESET to return In-Reply-To: <20201229160059.64135-1-dbrazdil@google.com> References: <20201229160059.64135-1-dbrazdil@google.com> User-Agent: Roundcube Webmail/1.4.9 Message-ID: <229d84b8d7818a170adf489535ea2d43@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: dbrazdil@google.com, kvmarm@lists.cs.columbia.edu, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, lorenzo.pieralisi@arm.com, sudeep.holla@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi David, On 2020-12-29 16:00, David Brazdil wrote: > The KVM/arm64 PSCI relay assumes that SYSTEM_OFF and SYSTEM_RESET > should > not return, as dictated by the PSCI spec. However, there is firmware > out > there which breaks this assumption, leading to a hyp panic. Make KVM > more robust to broken firmware by allowing these to return. > > Signed-off-by: David Brazdil > --- > arch/arm64/kvm/hyp/nvhe/psci-relay.c | 13 +++++-------- > 1 file changed, 5 insertions(+), 8 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/nvhe/psci-relay.c > b/arch/arm64/kvm/hyp/nvhe/psci-relay.c > index e3947846ffcb..8e7128cb7667 100644 > --- a/arch/arm64/kvm/hyp/nvhe/psci-relay.c > +++ b/arch/arm64/kvm/hyp/nvhe/psci-relay.c > @@ -77,12 +77,6 @@ static unsigned long psci_forward(struct > kvm_cpu_context *host_ctxt) > cpu_reg(host_ctxt, 2), cpu_reg(host_ctxt, 3)); > } > > -static __noreturn unsigned long psci_forward_noreturn(struct > kvm_cpu_context *host_ctxt) > -{ > - psci_forward(host_ctxt); > - hyp_panic(); /* unreachable */ > -} > - > static unsigned int find_cpu_id(u64 mpidr) > { > unsigned int i; > @@ -251,10 +245,13 @@ static unsigned long psci_0_2_handler(u64 > func_id, struct kvm_cpu_context *host_ > case PSCI_0_2_FN_MIGRATE_INFO_TYPE: > case PSCI_0_2_FN64_MIGRATE_INFO_UP_CPU: > return psci_forward(host_ctxt); > + /* > + * SYSTEM_OFF/RESET should not return according to the spec. > + * Allow it so as to stay robust to broken firmware. > + */ > case PSCI_0_2_FN_SYSTEM_OFF: > case PSCI_0_2_FN_SYSTEM_RESET: > - psci_forward_noreturn(host_ctxt); > - unreachable(); > + return psci_forward(host_ctxt); > case PSCI_0_2_FN64_CPU_SUSPEND: > return psci_cpu_suspend(func_id, host_ctxt); > case PSCI_0_2_FN64_CPU_ON: Thanks for having tracked this. I wonder whether we should also taint the kernel in this case, because this is completely unexpected, and a major spec violation. Ideally, we'd be able to detect this case and prevent pKVM from getting initialised at all, but I guess there is no way to detect the sucker without ... calling SYSTEM_RESET? M. -- Jazz is not dead. It just smells funny... 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=-14.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,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 E39D1C433E0 for ; Tue, 29 Dec 2020 17:16:48 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 5BA9922209 for ; Tue, 29 Dec 2020 17:16:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5BA9922209 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id B6B004B2A2; Tue, 29 Dec 2020 12:16:47 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu 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 47mofchRaDbk; Tue, 29 Dec 2020 12:16:46 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 843164B26D; Tue, 29 Dec 2020 12:16:46 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 017224B25A for ; Tue, 29 Dec 2020 12:16:46 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu 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 jTt07kiLQPKF for ; Tue, 29 Dec 2020 12:16:45 -0500 (EST) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id E6D1C4B24E for ; Tue, 29 Dec 2020 12:16:44 -0500 (EST) Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CC47A21D94; Tue, 29 Dec 2020 17:16:43 +0000 (UTC) Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94) (envelope-from ) id 1kuIbx-004Ri2-Kb; Tue, 29 Dec 2020 17:16:41 +0000 MIME-Version: 1.0 Date: Tue, 29 Dec 2020 17:16:41 +0000 From: Marc Zyngier To: David Brazdil Subject: Re: [PATCH] KVM: arm64: Allow PSCI SYSTEM_OFF/RESET to return In-Reply-To: <20201229160059.64135-1-dbrazdil@google.com> References: <20201229160059.64135-1-dbrazdil@google.com> User-Agent: Roundcube Webmail/1.4.9 Message-ID: <229d84b8d7818a170adf489535ea2d43@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: dbrazdil@google.com, kvmarm@lists.cs.columbia.edu, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, lorenzo.pieralisi@arm.com, sudeep.holla@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Cc: Lorenzo Pieralisi , Catalin Marinas , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Sudeep Holla , kernel-team@android.com, Will Deacon , kvmarm@lists.cs.columbia.edu X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu Hi David, On 2020-12-29 16:00, David Brazdil wrote: > The KVM/arm64 PSCI relay assumes that SYSTEM_OFF and SYSTEM_RESET > should > not return, as dictated by the PSCI spec. However, there is firmware > out > there which breaks this assumption, leading to a hyp panic. Make KVM > more robust to broken firmware by allowing these to return. > > Signed-off-by: David Brazdil > --- > arch/arm64/kvm/hyp/nvhe/psci-relay.c | 13 +++++-------- > 1 file changed, 5 insertions(+), 8 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/nvhe/psci-relay.c > b/arch/arm64/kvm/hyp/nvhe/psci-relay.c > index e3947846ffcb..8e7128cb7667 100644 > --- a/arch/arm64/kvm/hyp/nvhe/psci-relay.c > +++ b/arch/arm64/kvm/hyp/nvhe/psci-relay.c > @@ -77,12 +77,6 @@ static unsigned long psci_forward(struct > kvm_cpu_context *host_ctxt) > cpu_reg(host_ctxt, 2), cpu_reg(host_ctxt, 3)); > } > > -static __noreturn unsigned long psci_forward_noreturn(struct > kvm_cpu_context *host_ctxt) > -{ > - psci_forward(host_ctxt); > - hyp_panic(); /* unreachable */ > -} > - > static unsigned int find_cpu_id(u64 mpidr) > { > unsigned int i; > @@ -251,10 +245,13 @@ static unsigned long psci_0_2_handler(u64 > func_id, struct kvm_cpu_context *host_ > case PSCI_0_2_FN_MIGRATE_INFO_TYPE: > case PSCI_0_2_FN64_MIGRATE_INFO_UP_CPU: > return psci_forward(host_ctxt); > + /* > + * SYSTEM_OFF/RESET should not return according to the spec. > + * Allow it so as to stay robust to broken firmware. > + */ > case PSCI_0_2_FN_SYSTEM_OFF: > case PSCI_0_2_FN_SYSTEM_RESET: > - psci_forward_noreturn(host_ctxt); > - unreachable(); > + return psci_forward(host_ctxt); > case PSCI_0_2_FN64_CPU_SUSPEND: > return psci_cpu_suspend(func_id, host_ctxt); > case PSCI_0_2_FN64_CPU_ON: Thanks for having tracked this. I wonder whether we should also taint the kernel in this case, because this is completely unexpected, and a major spec violation. Ideally, we'd be able to detect this case and prevent pKVM from getting initialised at all, but I guess there is no way to detect the sucker without ... calling SYSTEM_RESET? M. -- Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm 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=-14.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 5DC93C433E0 for ; Tue, 29 Dec 2020 17:18:03 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 11E6820867 for ; Tue, 29 Dec 2020 17:18:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 11E6820867 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+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=merlin.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:Message-ID:References:In-Reply-To:Subject:To:From: Date:MIME-Version:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=MlNEAvOrZlP/AJYJJikfXRS6GSxavhAvimGqq9oxnJw=; b=2I7MbPkptdRhnkUj3l3OSOUT/ h+QW8+l4vSB+hEo36vrpb/B25tj8yv1BK1m0d9eTwUcET/h5KLCcNItsi/+uaDsRg0XJaC24mMIEh mzN4NVLkC4dLQIOKKH90xajrd3W/OTmtAdlrrFKs6ZHzeRMa/g2ThnLCYlGp4sSYkPrILN1FzdnIs OdFo+cQs0QHRQzSAgaCYkgIaUhte24LAtHLuCd5qkaygNyTQ92cIv7BiHnslNhRhV2m0hi2Q5sHmv R6xRooTnX+DTDkYJbHZ9YkXH+IZcZkr6aOS5Fy954T6rscrDgXiLN5diNIC/9B72ZECiwWxoGz36R gPLdu9bVA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kuIc3-00086a-Jl; Tue, 29 Dec 2020 17:16:47 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kuIc1-00085z-Dg for linux-arm-kernel@lists.infradead.org; Tue, 29 Dec 2020 17:16:46 +0000 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CC47A21D94; Tue, 29 Dec 2020 17:16:43 +0000 (UTC) Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94) (envelope-from ) id 1kuIbx-004Ri2-Kb; Tue, 29 Dec 2020 17:16:41 +0000 MIME-Version: 1.0 Date: Tue, 29 Dec 2020 17:16:41 +0000 From: Marc Zyngier To: David Brazdil Subject: Re: [PATCH] KVM: arm64: Allow PSCI SYSTEM_OFF/RESET to return In-Reply-To: <20201229160059.64135-1-dbrazdil@google.com> References: <20201229160059.64135-1-dbrazdil@google.com> User-Agent: Roundcube Webmail/1.4.9 Message-ID: <229d84b8d7818a170adf489535ea2d43@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: dbrazdil@google.com, kvmarm@lists.cs.columbia.edu, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, lorenzo.pieralisi@arm.com, sudeep.holla@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201229_121645_600235_0DC64803 X-CRM114-Status: GOOD ( 23.67 ) 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: Mark Rutland , Lorenzo Pieralisi , Suzuki K Poulose , Catalin Marinas , linux-kernel@vger.kernel.org, James Morse , linux-arm-kernel@lists.infradead.org, Sudeep Holla , kernel-team@android.com, Will Deacon , kvmarm@lists.cs.columbia.edu, Julien Thierry Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi David, On 2020-12-29 16:00, David Brazdil wrote: > The KVM/arm64 PSCI relay assumes that SYSTEM_OFF and SYSTEM_RESET > should > not return, as dictated by the PSCI spec. However, there is firmware > out > there which breaks this assumption, leading to a hyp panic. Make KVM > more robust to broken firmware by allowing these to return. > > Signed-off-by: David Brazdil > --- > arch/arm64/kvm/hyp/nvhe/psci-relay.c | 13 +++++-------- > 1 file changed, 5 insertions(+), 8 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/nvhe/psci-relay.c > b/arch/arm64/kvm/hyp/nvhe/psci-relay.c > index e3947846ffcb..8e7128cb7667 100644 > --- a/arch/arm64/kvm/hyp/nvhe/psci-relay.c > +++ b/arch/arm64/kvm/hyp/nvhe/psci-relay.c > @@ -77,12 +77,6 @@ static unsigned long psci_forward(struct > kvm_cpu_context *host_ctxt) > cpu_reg(host_ctxt, 2), cpu_reg(host_ctxt, 3)); > } > > -static __noreturn unsigned long psci_forward_noreturn(struct > kvm_cpu_context *host_ctxt) > -{ > - psci_forward(host_ctxt); > - hyp_panic(); /* unreachable */ > -} > - > static unsigned int find_cpu_id(u64 mpidr) > { > unsigned int i; > @@ -251,10 +245,13 @@ static unsigned long psci_0_2_handler(u64 > func_id, struct kvm_cpu_context *host_ > case PSCI_0_2_FN_MIGRATE_INFO_TYPE: > case PSCI_0_2_FN64_MIGRATE_INFO_UP_CPU: > return psci_forward(host_ctxt); > + /* > + * SYSTEM_OFF/RESET should not return according to the spec. > + * Allow it so as to stay robust to broken firmware. > + */ > case PSCI_0_2_FN_SYSTEM_OFF: > case PSCI_0_2_FN_SYSTEM_RESET: > - psci_forward_noreturn(host_ctxt); > - unreachable(); > + return psci_forward(host_ctxt); > case PSCI_0_2_FN64_CPU_SUSPEND: > return psci_cpu_suspend(func_id, host_ctxt); > case PSCI_0_2_FN64_CPU_ON: Thanks for having tracked this. I wonder whether we should also taint the kernel in this case, because this is completely unexpected, and a major spec violation. Ideally, we'd be able to detect this case and prevent pKVM from getting initialised at all, but I guess there is no way to detect the sucker without ... calling SYSTEM_RESET? M. -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel