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 BA1F3C31E40 for ; Mon, 12 Aug 2019 13:41:23 +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 8C1C4206C2 for ; Mon, 12 Aug 2019 13:41:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8C1C4206C2 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]:45654 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hxAZe-0002jd-QW for qemu-devel@archiver.kernel.org; Mon, 12 Aug 2019 09:41:22 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:56025) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hxAZC-0002Gm-E0 for qemu-devel@nongnu.org; Mon, 12 Aug 2019 09:40:55 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hxAZB-0000mM-7w for qemu-devel@nongnu.org; Mon, 12 Aug 2019 09:40:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37618) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hxAZB-0000lx-1p; Mon, 12 Aug 2019 09:40:53 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3A31E30084AD; Mon, 12 Aug 2019 13:40:52 +0000 (UTC) Received: from gondolin (dhcp-192-181.str.redhat.com [10.33.192.181]) by smtp.corp.redhat.com (Postfix) with ESMTP id A54E62FC68; Mon, 12 Aug 2019 13:40:47 +0000 (UTC) Date: Mon, 12 Aug 2019 15:40:45 +0200 From: Cornelia Huck To: David Hildenbrand Message-ID: <20190812154045.10393873.cohuck@redhat.com> In-Reply-To: References: <20190805152947.28536-1-david@redhat.com> <20190805152947.28536-2-david@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 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.40]); Mon, 12 Aug 2019 13:40:52 +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 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? > > In Linux, code+data will luckily usually have the same virtual->physical > tables, so it's not a real issue. > > > > > So maybe we need a proper MemTxAttrs bit or something similar for > > distinguishing instruction accesses from data accesses here? > > There would first have to be a way to ask "get_phys_page_debug" to get > code or data for this to make sense. Right now we used it to get code. I'm wondering if we're able to do better; but if the code/data distinction is not considered in architecture independent code, probably not easily.