From patchwork Sun Jun 25 22:19:56 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Aurelien Jarno X-Patchwork-Id: 780553 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3wwmpt5YYfz9s3w for ; Mon, 26 Jun 2017 08:20:37 +1000 (AEST) Received: from localhost ([::1]:44022 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dPFtS-0005oX-8X for incoming@patchwork.ozlabs.org; Sun, 25 Jun 2017 18:20:34 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48791) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dPFt6-0005oA-24 for qemu-devel@nongnu.org; Sun, 25 Jun 2017 18:20:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dPFt4-0007bo-QK for qemu-devel@nongnu.org; Sun, 25 Jun 2017 18:20:12 -0400 Received: from hall.aurel32.net ([2001:bc8:30d7:100::1]:56492) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dPFt4-0007VL-K6 for qemu-devel@nongnu.org; Sun, 25 Jun 2017 18:20:10 -0400 Received: from [2001:bc8:30d7:120:9bb5:8936:7e6a:9e36] (helo=ohm.rr44.fr) by hall.aurel32.net with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1dPFsr-0001sU-LN; Mon, 26 Jun 2017 00:19:57 +0200 Received: from aurel32 by ohm.rr44.fr with local (Exim 4.89) (envelope-from ) id 1dPFsq-0007Qq-UU; Mon, 26 Jun 2017 00:19:56 +0200 Date: Mon, 26 Jun 2017 00:19:56 +0200 From: Aurelien Jarno To: David Hildenbrand Message-ID: <20170625221956.rda2cls2ex7icapa@aurel32.net> References: <20170622231228.1050-1-david@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20170622231228.1050-1-david@redhat.com> User-Agent: NeoMutt/20170113 (1.7.2) X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2001:bc8:30d7:100::1 Subject: Re: [Qemu-devel] [PATCH v1] target-s390x: fix risbg handling X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: agraf@suse.de, thuth@redhat.com, qemu-devel@nongnu.org, rth@twiddle.net Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" On 2017-06-23 01:12, David Hildenbrand wrote: > If we have for example: r3 contains 0x00000000ffffffff > ec 33 3f bf 61 55 risbg %r3,%r3,63,191,97 > > We want to rotate 33 to the left and only keep MSB bit 63 of that. So the > result is then exactly 1 (we're reading the sign of the 32 bit value). > > Current code assumes that we can do that via an extract, which is not > true (at least not that easy) and produces a 0. I think the mistake there is that the rotation is done to the left, while in extract the "shift" is done to the right. The following patch should be enough: > Let's just get rid of this special handling. > > Signed-off-by: David Hildenbrand > --- > > This effectively allows to start a linux kernel, compiled for z10 using > the qemu model under tcg (with other patches currently on the list): > > qemu-system-s390x ... -cpu qemu,mvcos=on,stfle=on,ldisp=on,ldisphp=on, \ > eimm=on,stckf=on,csst=on,csst2=on,ginste=on, \ > exrl=on ... > > I found this by compiling the kvm-unit-tests for z10 and noticing > elementary selftests failing. The kernel would trigger weird > BUG_ONs very early while starting up, which basically gave not really > many hints of what was actually going wrong. > > target/s390x/translate.c | 6 ------ > 1 file changed, 6 deletions(-) But the patch is also correct. Reviewed-by: Aurelien Jarno --- a/target/s390x/translate.c +++ b/target/s390x/translate.c @@ -3441,8 +3441,8 @@ static ExitStatus op_risbg(DisasContext *s, DisasOps *o) } /* In some cases we can implement this with extract. */ - if (imask == 0 && pos == 0 && len > 0 && rot + len <= 64) { - tcg_gen_extract_i64(o->out, o->in2, rot, len); + if (imask == 0 && pos == 0 && len > 0 && rot - len >= 0) { + tcg_gen_extract_i64(o->out, o->in2, 64 - rot, len); return NO_EXIT;