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 7979CC433F5 for ; Wed, 9 Feb 2022 18:57:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238659AbiBIS5k (ORCPT ); Wed, 9 Feb 2022 13:57:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33882 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241339AbiBIS5D (ORCPT ); Wed, 9 Feb 2022 13:57:03 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D44F4C05CBB6; Wed, 9 Feb 2022 10:57:05 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 72FB7617DB; Wed, 9 Feb 2022 18:57:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id ABF53C340E7; Wed, 9 Feb 2022 18:57:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1644433024; bh=H9AOZ4VvMnz+eej4Jp2A9tk40+GzB/tTtRcrZcb3Tu4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GUEvoZZkwANj4hqYmEU9t4bXi5nvP3mjvz5yxWDI1mXbu4fg7DoPSTZwaGQYhihoi B4189XNIv9RckSyDeAXkGH8Z0KFRNWyq7BzRfoR386ZiaNU1qjtWS44CTHz0k/eqda 5hoqgJn1NomU42J91XkdApP/7aar+q+Cp3iHRokdArTOU5biXUYdgLTsBuNIz1XxOe hmHxlPlThECwe/vDSrO2ez1PCs/kSdlsmE213V7IUtYTWao6QQQOzhEaEQo5UBQ9Vc I1eKpV6zQkO+PcSLx212nGqykv2CS9hJ2y3X011yLFkSDZKnlpm57dwtmeJs5/ItAk WT/MV6T1QvdXQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Sean Christopherson , Liam Merwick , Paolo Bonzini , Sasha Levin , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, kvm@vger.kernel.org Subject: [PATCH MANUALSEL 5.15 5/8] KVM: SVM: Don't kill SEV guest if SMAP erratum triggers in usermode Date: Wed, 9 Feb 2022 13:56:50 -0500 Message-Id: <20220209185653.48833-5-sashal@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220209185653.48833-1-sashal@kernel.org> References: <20220209185653.48833-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Sean Christopherson [ Upstream commit cdf85e0c5dc766fc7fc779466280e454a6d04f87 ] Inject a #GP instead of synthesizing triple fault to try to avoid killing the guest if emulation of an SEV guest fails due to encountering the SMAP erratum. The injected #GP may still be fatal to the guest, e.g. if the userspace process is providing critical functionality, but KVM should make every attempt to keep the guest alive. Signed-off-by: Sean Christopherson Reviewed-by: Liam Merwick Message-Id: <20220120010719.711476-10-seanjc@google.com> Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- arch/x86/kvm/svm/svm.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 980abc437cdaa..f05aa7290267d 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4473,7 +4473,21 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, void *insn, int i is_user = svm_get_cpl(vcpu) == 3; if (smap && (!smep || is_user)) { pr_err_ratelimited("KVM: SEV Guest triggered AMD Erratum 1096\n"); - kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu); + + /* + * If the fault occurred in userspace, arbitrarily inject #GP + * to avoid killing the guest and to hopefully avoid confusing + * the guest kernel too much, e.g. injecting #PF would not be + * coherent with respect to the guest's page tables. Request + * triple fault if the fault occurred in the kernel as there's + * no fault that KVM can inject without confusing the guest. + * In practice, the triple fault is moot as no sane SEV kernel + * will execute from user memory while also running with SMAP=1. + */ + if (is_user) + kvm_inject_gp(vcpu, 0); + else + kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu); } return false; -- 2.34.1