From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x225JADCEXY8F4XXiQlcQ6E5SQqyCvNXZGv2nO3us9z9tIl+neeskO541BiQ0gNcOug7qseaJ ARC-Seal: i=1; a=rsa-sha256; t=1518005849; cv=none; d=google.com; s=arc-20160816; b=SNVvvM8i7q4sOnTwXG4HKSjEOL8IV5x9YR19lAX0xBPzig9mB/t6jF0HlKiZbmJCq7 6hDxmUeOQZrSOnH1uXvmQ8G1yAMM022OYL4Wf1mP59zKQ3uAqobG6Jx78qLuXmEqzpXL 0Ss6ZTolCaqgbutPx8pj380A/cyodIRzHDkIvPJXTHz5cysTB01GqCMvvbonnDki+zT2 0GpOQb2Gb1c21B4RLkz+68WYVtpodH6fOjkYUnTeRQwwuKWYMpe4DiEgN77Gt+YIKAGy P+WjztTGunVsiQblDc9lcFEnmGpKS6OOQ3mKkCyxikVY67oJDuHUuIyaMyPLgECqjDmv 142A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=message-id:content-transfer-encoding:mime-version:references :in-reply-to:subject:cc:to:from:date:arc-authentication-results; bh=rfzE0+NIbwOdLJcF18W1eVgNGACILKKRP8WSxcGkXc0=; b=h1QBlwZdCZIYO9krO3J7zFhNC20aEMVnaZ1WdF0ksIuoK9eHPBrwmHFEZRZJbQkfza pzOUWBIVu2MmpdyMtITUmhPX0fGR9Yg3xILbyH4TXnlkUOx03mM92w6IMqe+YySR7lMx 4WM406802WK06drBwqiX/v8GL+2EiamWTOHDGpiLOc7lcK91G6z9d8kqQz4PFJsOyRqK y2VNxHXH4Ur6duFEjrueJ7K+LJJpRX2NUg/EuQUCt9acnooxZdUkP3/503/1pr3CfHYA wo998Vhk62uj6NhK06QWEi9HF60bsUgynnJKpitm1mQbuumOjlEp2txEo+q0/VVLSiw2 vaxQ== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of schwidefsky@de.ibm.com designates 148.163.156.1 as permitted sender) smtp.mailfrom=schwidefsky@de.ibm.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=ibm.com Authentication-Results: mx.google.com; spf=pass (google.com: domain of schwidefsky@de.ibm.com designates 148.163.156.1 as permitted sender) smtp.mailfrom=schwidefsky@de.ibm.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=ibm.com Date: Wed, 7 Feb 2018 13:17:19 +0100 From: Martin Schwidefsky To: David Woodhouse , Linus Torvalds Cc: Pavel Machek , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, Heiko Carstens , Christian Borntraeger , Cornelia Huck , David Hildenbrand , Greg Kroah-Hartman , Jon Masters , Marcus Meissner , Jiri Kosina , Dominik Brodowski , Alan Cox Subject: Re: [PATCH 6/6] s390: introduce execute-trampolines for branches In-Reply-To: <1518005275.3677.112.camel@infradead.org> References: <1517986811-27819-1-git-send-email-schwidefsky@de.ibm.com> <1517986811-27819-7-git-send-email-schwidefsky@de.ibm.com> <20180207100726.GB31392@amd> <1518005275.3677.112.camel@infradead.org> X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 x-cbid: 18020712-0012-0000-0000-000005AC4A7C X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18020712-0013-0000-0000-00001928018C Message-Id: <20180207131719.4aeb316e@mschwideX1> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-02-07_04:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1802070154 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1591724559737732044?= X-GMAIL-MSGID: =?utf-8?q?1591744501884839321?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Wed, 07 Feb 2018 12:07:55 +0000 David Woodhouse wrote: > On Wed, 2018-02-07 at 11:07 +0100, Pavel Machek wrote: > > This is really unfortunate naming of kernel option. > >=20 > > spectre_v2=3Doff sounds like we are turning the "bug" off, but i somehow > > suspect you are turning the bug _workaround_ off. =20 >=20 > That's consistent with what we have on x86. >=20 > > > +ifdef CONFIG_EXPOLINE > > > +=C2=A0=C2=A0ifeq ($(call cc-option-yn,$(CC_FLAGS_MARCH) -mindirect-b= ranch=3Dthunk),y) > > > +=C2=A0=C2=A0=C2=A0=C2=A0CC_FLAGS_EXPOLINE :=3D -mindirect-branch=3Dt= hunk > > > +=C2=A0=C2=A0=C2=A0=C2=A0CC_FLAGS_EXPOLINE +=3D -mfunction-return=3Dt= hunk > > > +=C2=A0=C2=A0=C2=A0=C2=A0CC_FLAGS_EXPOLINE +=3D -mindirect-branch-tab= le > > > +=C2=A0=C2=A0=C2=A0=C2=A0export CC_FLAGS_EXPOLINE > > > +=C2=A0=C2=A0=C2=A0=C2=A0cflags-y +=3D $(CC_FLAGS_EXPOLINE) > > > +=C2=A0=C2=A0else > > > +=C2=A0=C2=A0=C2=A0=C2=A0$(warning "Your gcc lacks the -mindirect-bra= nch=3D option") > > > +=C2=A0=C2=A0endif > > > +endif =20 >=20 > That isn't, though. Linus asked us to drop the $(warning) part. >=20 > ... and then spent a week building with a non-retpoline compiler and > not noticing, so he might have changed his mind ;) I found the warning to have some value, it helps for the case where my fingers are faster than my brain and I type "make" instead of "smake" which uses the alternative compiler with the required support. @Linus: do you want a warning or prefer not to have one ? --=20 blue skies, Martin. "Reality continues to ruin my life." - Calvin.