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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS 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 A50F7C433DF for ; Wed, 8 Jul 2020 08:18:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7B3342078C for ; Wed, 8 Jul 2020 08:18:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="SymsVca5" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727817AbgGHISD (ORCPT ); Wed, 8 Jul 2020 04:18:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48602 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725747AbgGHISD (ORCPT ); Wed, 8 Jul 2020 04:18:03 -0400 Received: from mail-oi1-x243.google.com (mail-oi1-x243.google.com [IPv6:2607:f8b0:4864:20::243]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C6A97C08C5DC; Wed, 8 Jul 2020 01:18:02 -0700 (PDT) Received: by mail-oi1-x243.google.com with SMTP id r8so37125056oij.5; Wed, 08 Jul 2020 01:18:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=/qD1naS8wsd2EhVt/M+vsUBKc2VxlIMTUtCT5APBmb8=; b=SymsVca5pFQCCFaUMvCW+p8zXKoPW57/AifVo6loHj3G3ZMuNEdPndUSr67k3LQD6O IONuzo1dRqgSK2pmyDmlbqpVHGMAdsbsKkDSUXaLMcAca1HvYtgK1fVgF0u1ao4srH3L 9eMZf/UYwCL2bEpTdphwhk/g7eflRo8nH9TacBib2eMBARWQRkBcB/H/tVX0S2a1kvqN 81Ha4VnR7EuXeeVcoc4F7NmucsKwaWxkZy6uI5v9JRt92cwO091o9CfBZr2P15NlMBdS 0iZYVPYAs2CBP90xbu5S+1y4Egp1hO53wrfSwx/q5SA47/I1aA4JOMtJVIgnRMnvft0U IvkQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=/qD1naS8wsd2EhVt/M+vsUBKc2VxlIMTUtCT5APBmb8=; b=b2PjG90NFVSSpgHcIynHEXKglrJETPB1ClBQOK1Y4I0pEw3w5sTTSeH614LR0mv0Xx phjgVOUUwIAtbPQUoV0ccdmBb+c/2FQ/nyjm8+n6quZAHISb8etek8xFvVAqasaEfG/j n3ve90SKImO6tOEA1wt/Z/p3x3reljEGX9FEFUsHro+xAgxmT/0MmJwvqHfKhi8KjmbY 0JuNdxoFwc3U/DJxGl6ZFy6Aezr32iiHiMJ6gcvVFc5fSanT2aASiM88WRzUKSt/Mg8o l+XJgQL6b4k7svxf4D9Rt+/VvQ5j5tpg1dhlVjG78K0B84Eg+EJ3xAS4lQep2pHhTLmg Z3Xg== X-Gm-Message-State: AOAM533QroOWtehpFOBU+MWM/26PiYlry/Ehyduveba11MlOlZvvBJ8W jZZkRSzm8Z6ePbJq2OMpE2z2wjd1eiAQYFcRKqk= X-Google-Smtp-Source: ABdhPJw/tiA3BCQR7zpDMd7jSoB9EFjDAwhK4Vb03FQ74u/mEXX7r77cGZ+tStwn8KI+qeHVppi8LmNYOypyLJ7MQAY= X-Received: by 2002:aca:d643:: with SMTP id n64mr6264105oig.33.1594196282195; Wed, 08 Jul 2020 01:18:02 -0700 (PDT) MIME-Version: 1.0 References: <20200417163843.71624-1-pbonzini@redhat.com> <20200417163843.71624-2-pbonzini@redhat.com> In-Reply-To: <20200417163843.71624-2-pbonzini@redhat.com> From: Wanpeng Li Date: Wed, 8 Jul 2020 16:17:51 +0800 Message-ID: Subject: Re: [PATCH 1/2] KVM: SVM: avoid infinite loop on NPF from bad address To: Paolo Bonzini Cc: LKML , kvm , Sean Christopherson , "# v3 . 10+" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 18 Apr 2020 at 00:39, Paolo Bonzini wrote: > > When a nested page fault is taken from an address that does not have > a memslot associated to it, kvm_mmu_do_page_fault returns RET_PF_EMULATE > (via mmu_set_spte) and kvm_mmu_page_fault then invokes svm_need_emulation_on_page_fault. > > The default answer there is to return false, but in this case this just > causes the page fault to be retried ad libitum. Since this is not a > fast path, and the only other case where it is taken is an erratum, > just stick a kvm_vcpu_gfn_to_memslot check in there to detect the > common case where the erratum is not happening. > > This fixes an infinite loop in the new set_memory_region_test. > > Fixes: 05d5a4863525 ("KVM: SVM: Workaround errata#1096 (insn_len maybe zero on SMAP violation)") > Cc: stable@vger.kernel.org > Signed-off-by: Paolo Bonzini > --- > arch/x86/kvm/svm/svm.c | 7 +++++++ > virt/kvm/kvm_main.c | 1 + > 2 files changed, 8 insertions(+) > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index a91e397d6750..c86f7278509b 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -3837,6 +3837,13 @@ static bool svm_need_emulation_on_page_fault(struct kvm_vcpu *vcpu) > bool smap = cr4 & X86_CR4_SMAP; > bool is_user = svm_get_cpl(vcpu) == 3; > > + /* > + * If RIP is invalid, go ahead with emulation which will cause an > + * internal error exit. > + */ > + if (!kvm_vcpu_gfn_to_memslot(vcpu, kvm_rip_read(vcpu) >> PAGE_SHIFT)) > + return true; > + > /* > * Detect and workaround Errata 1096 Fam_17h_00_0Fh. > * > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index e2f60e313c87..e7436d054305 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -1602,6 +1602,7 @@ struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn > { > return __gfn_to_memslot(kvm_vcpu_memslots(vcpu), gfn); > } > +EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_memslot); This commit incurs the linux guest fails to boot once add --overcommit cpu-pm=on or not intercept hlt instruction, any thoughts? <...>-35787 [038] .... 2825.959082: kvm_exit: vcpu 1 reason npf rip 0xfd11d info 100000014 fd000 <...>-35788 [037] .... 2825.959082: kvm_exit: vcpu 2 reason npf rip 0xfd11d info 100000014 fd000 <...>-35789 [036] .... 2825.959082: kvm_exit: vcpu 3 reason npf rip 0xfd11d info 100000014 fd000 <...>-35788 [037] .... 2825.959082: kvm_page_fault: address fd000 error_code 14 <...>-35789 [036] .... 2825.959082: kvm_page_fault: address fd000 error_code 14 <...>-35787 [038] .... 2825.959083: kvm_page_fault: address fd000 error_code 14 <...>-35788 [037] .... 2825.959086: kvm_emulate_insn: 0:fd11d: (prot32) <...>-35788 [037] .... 2825.959086: kvm_emulate_insn: 0:fd11d: (prot32) failed <...>-35789 [036] .... 2825.959087: kvm_emulate_insn: 0:fd11d: (prot32) <...>-35789 [036] .... 2825.959087: kvm_emulate_insn: 0:fd11d: (prot32) failed <...>-35788 [037] .... 2825.959087: kvm_fpu: unload <...>-35787 [038] .... 2825.959087: kvm_emulate_insn: 0:fd11d: (prot32) <...>-35787 [038] .... 2825.959087: kvm_emulate_insn: 0:fd11d: (prot32) failed <...>-35789 [036] .... 2825.959087: kvm_fpu: unload <...>-35787 [038] .... 2825.959088: kvm_fpu: unload <...>-35788 [037] .... 2825.959088: kvm_userspace_exit: reason KVM_EXIT_INTERNAL_ERROR (17) <...>-35789 [036] .... 2825.959089: kvm_userspace_exit: reason KVM_EXIT_INTERNAL_ERROR (17) <...>-35787 [038] .... 2825.959089: kvm_userspace_exit: reason KVM_EXIT_INTERNAL_ERROR (17)