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=-10.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,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 94478C5DF9D for ; Wed, 28 Oct 2020 22:19:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 487C2206F4 for ; Wed, 28 Oct 2020 22:19:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603923543; bh=NQhHQntLZbnUoS/6yc85poCYnBYFJB0tEBEoFqmqy00=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=DVJvx5LfFPzI2yF3AK6LjGBL+L0p+rx2sWuTQQXEJhQdpezC31R+IQN8F1Ri463hB 4zauCATj10csn+nommQz1ADo+0DfgCWrWhd9HgPWbtXB6L9CDxDYtxjeLVfS2ZFFYM 5+AlQ4KFmwpoXQr1C0dkfp+SSsucK4+LlPG8Jszo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731530AbgJ1WST (ORCPT ); Wed, 28 Oct 2020 18:18:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:60548 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731778AbgJ1WRp (ORCPT ); Wed, 28 Oct 2020 18:17:45 -0400 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 E4C1A246A5; Wed, 28 Oct 2020 10:03:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603879432; bh=NQhHQntLZbnUoS/6yc85poCYnBYFJB0tEBEoFqmqy00=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Quj9xe/wOc2qoLkwpTkRu8kIGxN+5+Zi3TDhn8yy78/ocub3k4+QHI3CIO/oKpqZc 32xw0NGlkrwLeWAN26hnncv/68VVX9pJZia/iMoSzI2FFq3yt0ckWHtrOg3exEjslz XRJ9TXyJAsjshRSW4E2cTqU9vM/gnKoz1cYTMsiQ= 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 1kXiJ3-0053dT-NI; Wed, 28 Oct 2020 10:03:49 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Wed, 28 Oct 2020 10:03:49 +0000 From: Marc Zyngier To: Will Deacon Cc: Stephen Boyd , Catalin Marinas , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Andre Przywara , Steven Price , stable@vger.kernel.org Subject: Re: [PATCH v3] KVM: arm64: ARM_SMCCC_ARCH_WORKAROUND_1 doesn't return SMCCC_RET_NOT_REQUIRED In-Reply-To: <20201026132533.GC24349@willie-the-truck> References: <20201023154751.1973872-1-swboyd@chromium.org> <20201026132533.GC24349@willie-the-truck> User-Agent: Roundcube Webmail/1.4.9 Message-ID: <5e9bded886e31f7c7aaee195e6c373e1@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: will@kernel.org, swboyd@chromium.org, catalin.marinas@arm.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, andre.przywara@arm.com, steven.price@arm.com, stable@vger.kernel.org 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 On 2020-10-26 13:25, Will Deacon wrote: > On Fri, Oct 23, 2020 at 08:47:50AM -0700, Stephen Boyd wrote: >> According to the SMCCC spec[1](7.5.2 Discovery) the >> ARM_SMCCC_ARCH_WORKAROUND_1 function id only returns 0, 1, and >> SMCCC_RET_NOT_SUPPORTED. >> >> 0 is "workaround required and safe to call this function" >> 1 is "workaround not required but safe to call this function" >> SMCCC_RET_NOT_SUPPORTED is "might be vulnerable or might not be, who >> knows, I give up!" >> >> SMCCC_RET_NOT_SUPPORTED might as well mean "workaround required, >> except >> calling this function may not work because it isn't implemented in >> some >> cases". Wonderful. We map this SMC call to >> >> 0 is SPECTRE_MITIGATED >> 1 is SPECTRE_UNAFFECTED >> SMCCC_RET_NOT_SUPPORTED is SPECTRE_VULNERABLE >> >> For KVM hypercalls (hvc), we've implemented this function id to return >> SMCCC_RET_NOT_SUPPORTED, 0, and SMCCC_RET_NOT_REQUIRED. One of those >> isn't supposed to be there. Per the code we call >> arm64_get_spectre_v2_state() to figure out what to return for this >> feature discovery call. >> >> 0 is SPECTRE_MITIGATED >> SMCCC_RET_NOT_REQUIRED is SPECTRE_UNAFFECTED >> SMCCC_RET_NOT_SUPPORTED is SPECTRE_VULNERABLE >> >> Let's clean this up so that KVM tells the guest this mapping: >> >> 0 is SPECTRE_MITIGATED >> 1 is SPECTRE_UNAFFECTED >> SMCCC_RET_NOT_SUPPORTED is SPECTRE_VULNERABLE >> >> Note: SMCCC_RET_NOT_AFFECTED is 1 but isn't part of the SMCCC spec >> >> Cc: Andre Przywara >> Cc: Steven Price >> Cc: Marc Zyngier >> Cc: stable@vger.kernel.org >> Link: https://developer.arm.com/documentation/den0028/latest [1] >> Fixes: c118bbb52743 ("arm64: KVM: Propagate full Spectre v2 workaround >> state to KVM guests") >> Signed-off-by: Stephen Boyd >> --- >> >> I see that before commit c118bbb52743 ("arm64: KVM: Propagate full >> Spectre v2 workaround state to KVM guests") we had this mapping: >> >> 0 is SPECTRE_MITIGATED >> SMCCC_RET_NOT_SUPPORTED is SPECTRE_VULNERABLE >> >> so the return value '1' wasn't there then. Once the commit was merged >> we >> introduced the notion of NOT_REQUIRED here when it shouldn't have been >> introduced. >> >> Changes from v2: >> * Moved define to header file and used it >> >> Changes from v1: >> * Way longer commit text, more background (sorry) >> * Dropped proton-pack part because it was wrong >> * Rebased onto other patch accepted upstream >> >> arch/arm64/kernel/proton-pack.c | 2 -- >> arch/arm64/kvm/hypercalls.c | 2 +- >> include/linux/arm-smccc.h | 2 ++ >> 3 files changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/arch/arm64/kernel/proton-pack.c >> b/arch/arm64/kernel/proton-pack.c >> index 25f3c80b5ffe..c18eb7d41274 100644 >> --- a/arch/arm64/kernel/proton-pack.c >> +++ b/arch/arm64/kernel/proton-pack.c >> @@ -135,8 +135,6 @@ static enum mitigation_state >> spectre_v2_get_cpu_hw_mitigation_state(void) >> return SPECTRE_VULNERABLE; >> } >> >> -#define SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED (1) >> - >> static enum mitigation_state >> spectre_v2_get_cpu_fw_mitigation_state(void) >> { >> int ret; >> diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c >> index 9824025ccc5c..25ea4ecb6449 100644 >> --- a/arch/arm64/kvm/hypercalls.c >> +++ b/arch/arm64/kvm/hypercalls.c >> @@ -31,7 +31,7 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu) >> val = SMCCC_RET_SUCCESS; >> break; >> case SPECTRE_UNAFFECTED: >> - val = SMCCC_RET_NOT_REQUIRED; >> + val = SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED; >> break; >> } >> break; >> diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h >> index 15c706fb0a37..0e50ba3e88d7 100644 >> --- a/include/linux/arm-smccc.h >> +++ b/include/linux/arm-smccc.h >> @@ -86,6 +86,8 @@ >> ARM_SMCCC_SMC_32, \ >> 0, 0x7fff) >> >> +#define SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED 1 > > I thought we'd stick this in asm/spectre.h, but here is also good: > > Acked-by: Will Deacon Acked-by: Marc Zyngier Will, if you're about to send fixes to Linus, can you please pick this one up? M. -- Jazz is not dead. It just smells funny...