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=-11.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, 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 D352AC43381 for ; Tue, 12 Jan 2021 15:48:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A6CD123132 for ; Tue, 12 Jan 2021 15:48:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404987AbhALPsB (ORCPT ); Tue, 12 Jan 2021 10:48:01 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:46045 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405525AbhALPsB (ORCPT ); Tue, 12 Jan 2021 10:48:01 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1610466395; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4jiwV7AuQsPxZcRY14JFnrQvYVeLgEnELmlaS2CrL8E=; b=dfjezba+UybJ3R6oxVTWw4MebYES/iVLJ/8eLhCtcEbc8Wm9NjWUnoOjDamEDM/+9JumP9 UlUVS3gxcxF6oNVtKVOjIpWXyRkxmdIJtFDuuDDL+HSqfJlNU1bkCfD9q7hOvOEAB8K86J 1gBB9qh1uNLYPb8AL1cqGvRPuIptiV0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-584-vobvzLUAPUyzqf0r_KCbag-1; Tue, 12 Jan 2021 10:46:31 -0500 X-MC-Unique: vobvzLUAPUyzqf0r_KCbag-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 95388100C66E; Tue, 12 Jan 2021 15:46:27 +0000 (UTC) Received: from gigantic.usersys.redhat.com (helium.bos.redhat.com [10.18.17.132]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DBC8077BF5; Tue, 12 Jan 2021 15:46:25 +0000 (UTC) From: Bandan Das To: Andy Lutomirski Cc: Maxim Levitsky , Vitaly Kuznetsov , Wei Huang , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, pbonzini@redhat.com, seanjc@google.com, joro@8bytes.org, bp@alien8.de, tglx@linutronix.de, mingo@redhat.com, x86@kernel.org, jmattson@google.com, wanpengli@tencent.com, dgilbert@redhat.com Subject: Re: [PATCH 1/2] KVM: x86: Add emulation support for #GP triggered by VM instructions References: <9f3b8e3dca453c13867c5c6b61645b9b58d68f61.camel@redhat.com> Date: Tue, 12 Jan 2021 10:46:25 -0500 In-Reply-To: (Andy Lutomirski's message of "Tue, 12 Jan 2021 07:22:41 -0800") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Andy Lutomirski writes: ... >>>>> #endif diff --git a/arch/x86/kvm/mmu/mmu.c >>>>> b/arch/x86/kvm/mmu/mmu.c index 6d16481aa29d..c5c4aaf01a1a 100644 >>>>> --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ >>>>> -50,6 +50,7 @@ #include #include #include >>>>> +#include #include >>>>> "trace.h" >>>>>=20 >>>>> extern bool itlb_multihit_kvm_mitigation; @@ -5675,6 +5676,12 @@ >>>>> void kvm_mmu_slot_set_dirty(struct kvm *kvm, } >>>>> EXPORT_SYMBOL_GPL(kvm_mmu_slot_set_dirty); >>>>>=20 >>>>> +bool kvm_is_host_reserved_region(u64 gpa) +{ + return >>>>> e820__mbapped_raw_any(gpa-1, gpa+1, E820_TYPE_RESERVED); +} >>>> While _e820__mapped_any()'s doc says '.. checks if any part of >>>> the range is mapped ..' it seems to me that the real >>>> check is [start, end) so we should use 'gpa' instead of 'gpa-1', >>>> no? >>> Why do you need to check GPA at all? >>>=20 >> To reduce the scope of the workaround. >>=20 >> The errata only happens when you use one of SVM instructions in the >> guest with EAX that happens to be inside one of the host reserved >> memory regions (for example SMM). > > This code reduces the scope of the workaround at the cost of > increasing the complexity of the workaround and adding a nonsensical > coupling between KVM and host details and adding an export that really > doesn=E2=80=99t deserve to be exported. > > Is there an actual concrete benefit to this check? Besides reducing the scope, my intention for the check was that we should know if such exceptions occur for any other undiscovered reasons with other memory types rather than hiding them under this workaround. Bandan