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=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 BAE72C31E40 for ; Mon, 12 Aug 2019 13:58:51 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8EB57206C2 for ; Mon, 12 Aug 2019 13:58:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8EB57206C2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:45832 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hxAqY-0007IX-RG for qemu-devel@archiver.kernel.org; Mon, 12 Aug 2019 09:58:50 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:58631) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hxAq9-0006hz-Uy for qemu-devel@nongnu.org; Mon, 12 Aug 2019 09:58:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hxAq8-000236-QT for qemu-devel@nongnu.org; Mon, 12 Aug 2019 09:58:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57466) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hxAq8-00021w-Gv; Mon, 12 Aug 2019 09:58:24 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 95DBEC075BD2; Mon, 12 Aug 2019 13:58:23 +0000 (UTC) Received: from gondolin (dhcp-192-181.str.redhat.com [10.33.192.181]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1D2057D489; Mon, 12 Aug 2019 13:58:19 +0000 (UTC) Date: Mon, 12 Aug 2019 15:58:17 +0200 From: Cornelia Huck To: David Hildenbrand Message-ID: <20190812155817.2edb133c.cohuck@redhat.com> In-Reply-To: <94fc262e-b8d7-df09-1461-f10a9874d954@redhat.com> References: <20190805152947.28536-1-david@redhat.com> <20190805152947.28536-2-david@redhat.com> <20190812154045.10393873.cohuck@redhat.com> <94fc262e-b8d7-df09-1461-f10a9874d954@redhat.com> Organization: Red Hat GmbH MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Mon, 12 Aug 2019 13:58:23 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH-for-4.2 v1 1/9] s390x/mmu: Better ASC selection in s390_cpu_get_phys_page_debug() X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Thomas Huth , Janosch Frank , qemu-devel@nongnu.org, Ilya Leoshkevich , Halil Pasic , Christian Borntraeger , qemu-s390x@nongnu.org, Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, 12 Aug 2019 15:45:25 +0200 David Hildenbrand wrote: > On 12.08.19 15:40, Cornelia Huck wrote: > > On Mon, 12 Aug 2019 09:52:56 +0200 > > David Hildenbrand wrote: > > > >> On 12.08.19 09:12, Thomas Huth wrote: > >>> On 8/5/19 5:29 PM, David Hildenbrand wrote: > >>>> Let's select the ASC before calling the function and use MMU_DATA_LOAD. > >>>> This is a preparation to: > >>>> - Remove the ASC magic depending on the access mode from mmu_translate > >>>> - Implement IEP support, where we could run into access exceptions > >>>> trying to fetch instructions > >>>> > >>>> Signed-off-by: David Hildenbrand > >>>> --- > >>>> target/s390x/helper.c | 10 +++++++++- > >>>> 1 file changed, 9 insertions(+), 1 deletion(-) > >>>> > >>>> diff --git a/target/s390x/helper.c b/target/s390x/helper.c > >>>> index 13ae9909ad..08166558a0 100644 > >>>> --- a/target/s390x/helper.c > >>>> +++ b/target/s390x/helper.c > >>>> @@ -58,7 +58,15 @@ hwaddr s390_cpu_get_phys_page_debug(CPUState *cs, vaddr vaddr) > >>>> vaddr &= 0x7fffffff; > >>>> } > >>>> > >>>> - if (mmu_translate(env, vaddr, MMU_INST_FETCH, asc, &raddr, &prot, false)) { > >>>> + /* > >>>> + * We want to read the code, however, not run into access exceptions > >>> > >>> Is this really a safe assumption here that we always use this to > >>> translate code addresses and not data addresses? ... I don't think so. > >>> For example with the "gva2gpa" HMP command, I'd rather expect that it > >>> also works with the secondary space mode...? > >> > >> Well, it's what current code does. I am not changing that behavior. > > > > Agreed, that is not actively breaking something. > > > >> > >> While it is in general broken to have a single interface to debug > >> code+data (which is only a problem on s390x), it makes a lot of sense if > >> you think about single-stepping through disassembled code using the > >> gdbstub. Or dumping code where you crashed. > > > > What about the memsave interface? > > I guess the same problem: > > "save to disk virtual memory dump starting at @var{addr} of size > @var{size}" - which virtual memory (code vs. data)? These old interface > are really x86 specific (meaning: it made sense this way for x86) So, the general verdict is "gnarly interface, but at least not broken for Linux guests", I guess. > > I'd like to note that if our KVM guest is in AR mode, we would now no > longer be able to crash it :) (well, a nice side-effect of instruction > fetches not going via AR mode). Heh :) Q: What do we need to consider beyond Linux guests? Probably not much, given that they would be broken already...