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=-18.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 D60CEC433E0 for ; Sat, 6 Mar 2021 01:41:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AA8FD64FF0 for ; Sat, 6 Mar 2021 01:41:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229672AbhCFBki (ORCPT ); Fri, 5 Mar 2021 20:40:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37172 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229758AbhCFBkG (ORCPT ); Fri, 5 Mar 2021 20:40:06 -0500 Received: from mail-pj1-x102f.google.com (mail-pj1-x102f.google.com [IPv6:2607:f8b0:4864:20::102f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 505C7C061760 for ; Fri, 5 Mar 2021 17:40:06 -0800 (PST) Received: by mail-pj1-x102f.google.com with SMTP id ga23-20020a17090b0397b02900c0b81bbcd4so75328pjb.0 for ; Fri, 05 Mar 2021 17:40:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:mime-version:content-disposition :in-reply-to; bh=xX/55P6fzvPP+kG+riEc/RE6T+vgX3JT/FeKbV8wZec=; b=cqkjENhf6SfmvG3cJTO5IOLbDHJOY2IKbtMCIWiigCb/iJinZ+7WIlNn5WPNnlJjJk OlR0qk+8k/5RHOBFyZY1pL9CfTMZYtmADUwLHEiCBTwPz0F2OGa/PasdauGZw6/GaNnP wNVxyLoEq3mtVfd8E2/Co7Y6onzV1RcXYhY4v2Xr54AwfQ2wtcRfpdaoPWg6wdRd3n7J d9FVYBmQ/9C+XNJrCrYrbdJlIomB1TcsxvRNAyVV/cSZbaScNyhOFN6jhkLImiXKa6jq mvzAMUrm1+MyGBO0FFvxzo4kNXegZT7YU+/1CC0QYyBdnHnt0KuEVOcT5fRuCnAASykE Fwtw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:mime-version :content-disposition:in-reply-to; bh=xX/55P6fzvPP+kG+riEc/RE6T+vgX3JT/FeKbV8wZec=; b=iVtHuCc+NkjQ5S2ZH6ZzgruDLIxfNwkMJFpMU/sMKj7ChcRI1YQFzQShhQfvC5B4XF TuSAWeYmhFKMdxPmnFqYgQHdQZz4kVslFiDEic1+2Vvl1fVUl4I5LrallScjR/9842co 6nZZBVbBJHbEQuMEi+DnFY1wNWN7c+weIWQltyPuuWwiF2e3/WvoTULElspvhBz/jo/7 XdmhAQgbu6XrGA/CARO5tKyXHKUWWsf2oUA+AP/RH9wLQpnCy1gCeagaADqmrGsPgxXB qdFTSnOU0wDe3DAx7qWTaT9i6vWS1vM+y2gQPv/cHoBZHC/bC34rNz/U1tc6OScIW9yI r1kA== X-Gm-Message-State: AOAM532ia0UqyNnYdQ2a/skkr9rIT6vOzbu8xMpZRpVd2oSMXvtLChek Y5Rs4E6K/dlD3SlB0ufKfQdIyQ== X-Google-Smtp-Source: ABdhPJw4UarDJ5mYAf08tWOWBCaTWJdKCJjmp6ylq+RSgegSnMASdCGiDyV8GCT7AgWZ5jFf78sPNQ== X-Received: by 2002:a17:90a:f010:: with SMTP id bt16mr13191132pjb.116.1614994805665; Fri, 05 Mar 2021 17:40:05 -0800 (PST) Received: from google.com ([2620:15c:f:10:fc04:f9df:1efb:bf0c]) by smtp.gmail.com with ESMTPSA id g6sm3609630pfi.15.2021.03.05.17.40.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Mar 2021 17:40:04 -0800 (PST) Date: Fri, 5 Mar 2021 17:39:58 -0800 From: Sean Christopherson To: Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, vkuznets@redhat.com, mlevitsk@redhat.com, Jim Mattson Subject: Re: [PATCH 03/28] KVM: nSVM: inject exceptions via svm_check_nested_events Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200526172308.111575-4-pbonzini@redhat.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hopefully I got the In-Reply-To header right... On Thu, May 28, 2020, Paolo Bonzini wrote: > This allows exceptions injected by the emulator to be properly delivered > as vmexits. The code also becomes simpler, because we can just let all > L0-intercepted exceptions go through the usual path. In particular, our > emulation of the VMX #DB exit qualification is very much simplified, > because the vmexit injection path can use kvm_deliver_exception_payload > to update DR6. Sadly, it's also completely and utterly broken for #UD and #GP, and a bit sketchy for #AC. Unless KVM (L0) knowingly wants to override L1, e.g. KVM_GUESTDBG_* cases, KVM shouldn't do a damn thing except forward the exception to L1 if L1 wants the exception. ud_interception() and gp_interception() do quite a bit before forwarding the exception, and in the case of #UD, it's entirely possible the #UD will never get forwarded to L1. #GP is even more problematic because it's a contributory exception, and kvm_multiple_exception() is not equipped to check and handle nested intercepts before vectoring the exception, which means KVM will incorrectly escalate a #GP->#DF and #GP->#DF->Triple Fault instead of exiting to L1. That's a wee bit problematic since KVM also has a soon-to-be-fixed bug where it kills L1 on a Triple Fault in L2... I think this will fix the bugs, I'll properly test and post next week. diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 90a1704b5752..928e11646dca 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -926,11 +926,11 @@ static int nested_svm_intercept(struct vcpu_svm *svm) } case SVM_EXIT_EXCP_BASE ... SVM_EXIT_EXCP_BASE + 0x1f: { /* - * Host-intercepted exceptions have been checked already in - * nested_svm_exit_special. There is nothing to do here, - * the vmexit is injected by svm_check_nested_events. + * Note, KVM may already have snagged exceptions it wants to + * handle even if L1 also wants the exception, e.g. #MC. */ - vmexit = NESTED_EXIT_DONE; + if (vmcb_is_intercept(&svm->nested.ctl, exit_code)) + vmexit = NESTED_EXIT_DONE; break; } case SVM_EXIT_ERR: { @@ -1122,19 +1122,23 @@ int nested_svm_exit_special(struct vcpu_svm *svm) case SVM_EXIT_INTR: case SVM_EXIT_NMI: case SVM_EXIT_NPF: + case SVM_EXIT_EXCP_BASE + MC_VECTOR: return NESTED_EXIT_HOST; - case SVM_EXIT_EXCP_BASE ... SVM_EXIT_EXCP_BASE + 0x1f: { + case SVM_EXIT_EXCP_BASE + DB_VECTOR: + case SVM_EXIT_EXCP_BASE + BP_VECTOR: { + /* KVM gets first crack at #DBs and #BPs, if it wants them. */ u32 excp_bits = 1 << (exit_code - SVM_EXIT_EXCP_BASE); if (svm->vmcb01.ptr->control.intercepts[INTERCEPT_EXCEPTION] & excp_bits) return NESTED_EXIT_HOST; - else if (exit_code == SVM_EXIT_EXCP_BASE + PF_VECTOR && - svm->vcpu.arch.apf.host_apf_flags) - /* Trap async PF even if not shadowing */ - return NESTED_EXIT_HOST; break; } + case SVM_EXIT_EXCP_BASE + PF_VECTOR: + /* Trap async PF even if not shadowing */ + if (svm->vcpu.arch.apf.host_apf_flags) + return NESTED_EXIT_HOST; + break; default: break; }