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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 2A567C433E0 for ; Thu, 18 Mar 2021 09:25:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CDB4D64ED2 for ; Thu, 18 Mar 2021 09:25:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229905AbhCRJZE (ORCPT ); Thu, 18 Mar 2021 05:25:04 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:56608 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229664AbhCRJYi (ORCPT ); Thu, 18 Mar 2021 05:24:38 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616059478; 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=nykiyaeCBaGeYOGatXJD1GHSD/9h0gHc7oJWiCYB0Xs=; b=FktoBDO5YE2lZwVi+NOwIFS9ppnq8xWXZbL9gZzFbASwp9XEAfuiaRT3d558enuEokVhlY WOF314Jg1sXJjfgPxJ3dTPwnjetrXaJ9vBdYqjAXvY2UMHKxffVuTsWviwhDznc3ots7MB E6JR9/84O+ZcgnKButm1NMICeB/Ix+Y= 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-20-LJKfGCoxN-KNvB0lGcxgKQ-1; Thu, 18 Mar 2021 05:24:34 -0400 X-MC-Unique: LJKfGCoxN-KNvB0lGcxgKQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 836A41084C83; Thu, 18 Mar 2021 09:24:32 +0000 (UTC) Received: from starship (unknown [10.35.206.84]) by smtp.corp.redhat.com (Postfix) with ESMTP id 305C010013C1; Thu, 18 Mar 2021 09:24:26 +0000 (UTC) Message-ID: <8ba6676471dc8c8219e35d6a1695febaea20bb0b.camel@redhat.com> Subject: Re: [PATCH 3/3] KVM: SVM: allow to intercept all exceptions for debug From: Maxim Levitsky To: Joerg Roedel Cc: kvm@vger.kernel.org, Vitaly Kuznetsov , linux-kernel@vger.kernel.org, Thomas Gleixner , Wanpeng Li , Kieran Bingham , Jessica Yu , Jan Kiszka , Andrew Morton , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , Sean Christopherson , Jim Mattson , Borislav Petkov , Stefano Garzarella , "H. Peter Anvin" , Paolo Bonzini , Ingo Molnar , Borislav Petkov Date: Thu, 18 Mar 2021 11:24:25 +0200 In-Reply-To: References: <20210315221020.661693-1-mlevitsk@redhat.com> <20210315221020.661693-4-mlevitsk@redhat.com> <4116d6ce75a85faccfe7a2b3967528f0561974ae.camel@redhat.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5 (3.36.5-2.fc32) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2021-03-18 at 10:19 +0100, Joerg Roedel wrote: > On Tue, Mar 16, 2021 at 12:51:20PM +0200, Maxim Levitsky wrote: > > I agree but what is wrong with that? > > This is a debug feature, and it only can be enabled by the root, > > and so someone might actually want this case to happen > > (e.g to see if a SEV guest can cope with extra #VC exceptions). > > That doesn't make sense, we know that and SEV-ES guest can't cope with > extra #VC exceptions, so there is no point in testing this. It is more a > way to shot oneself into the foot for the user and a potential source of > bug reports for SEV-ES guests. But again this is a debug feature, and it is intended to allow the user to shoot himself in the foot. Bug reports for a debug feature are autoclosed. It is no different from say poking kernel memory with its built-in gdbstub, for example. Best regards, Maxim Levitsky > > > > I have nothing against not allowing this for SEV-ES guests though. > > What do you think? > > I think SEV-ES guests should only have the intercept bits set which > guests acutally support > > Regards, > > Joerg >