From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-3493875-1519408564-2-15118037628881708784 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.001, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, UNPARSEABLE_RELAY 0.001, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='CN', FromHeader='com', MailFrom='org' X-Spam-charsets: cc='utf-8', plain='us-ascii' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1519408563; b=StNyje7CvO8bZsZ3kErOr1jEdonZCb/oES9NBNJzA0U2EQI reoJmeIJE1LjegU9CURjGn9dItLhw7RydZkOC5OVe/n0iyc8TH2m6nf4BCdhFPtR 8h3OGwf70+UhAhMBNIFhPa/VybkZPLHPECiPWqAoy4lGS18mezoAPw7m+2CpXtGb a7M0HzBNkiLJi8PRqqxeDHDPHakxVfaIk1S1WIlDc3V4EXUM6ugRVcq6/2+brNHP 3nhpaU5TPvO1J5BMzWyIyzh1iOZ3Bdf+UXIiX9gLPtTPc2IPX8XKwJ1xvIO+ZSAI YCtZuOzYuXVFXmeQgOkZZt3KJuFQJmIX0MyKN2w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=date:from:to:cc:subject:message-id :references:mime-version:content-type:in-reply-to:sender :list-id; s=arctest; t=1519408563; bh=wbz7c00OjrHCPWRaf2gkkn6g8v quIXDxl0dOcCFiOxs=; b=RtKBmDVzrtj1pALKQkHyesQ5tA+ACV37lsvTSc5JYJ EFPImZdPzgd7g7+IwHwFUcE1luGhXJlaBEbBq1AmKi96DCtsa2t9Mg8s+Ji20zSn AKtLnKZHj/Kea8I+nivr9ttMek4ehdO4RpI6UGG374efwgSMqwEcvdr8B3i+Dzo5 e6xuIofTP1TRIIH63B8SXDcuPziqxynkdi7jJ6QhEaorfOSle4kSBUNWdE3+JIBZ p2xfsQbUWMf3X42LpUSBvoRRCaKgM4uzTgZQIHJOw26NVrqXejZLkZOPL1nCb3xn rsbJMJX4p6NGMTEzXZMzr0T/sbj34XpwvBhH24nCPs+w== ARC-Authentication-Results: i=1; mx1.messagingengine.com; arc=none (no signatures found); dkim=pass (2048-bit rsa key sha256) header.d=oracle.com header.i=@oracle.com header.b=TBSgKwZh x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=corp-2017-10-26; dmarc=pass (p=none,has-list-id=yes,d=none) header.from=oracle.com; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=oracle.com header.result=pass header_is_org_domain=yes Authentication-Results: mx1.messagingengine.com; arc=none (no signatures found); dkim=pass (2048-bit rsa key sha256) header.d=oracle.com header.i=@oracle.com header.b=TBSgKwZh x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=corp-2017-10-26; dmarc=pass (p=none,has-list-id=yes,d=none) header.from=oracle.com; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=oracle.com header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751420AbeBWR4A (ORCPT ); Fri, 23 Feb 2018 12:56:00 -0500 Received: from aserp2120.oracle.com ([141.146.126.78]:55956 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751351AbeBWRz7 (ORCPT ); Fri, 23 Feb 2018 12:55:59 -0500 Date: Fri, 23 Feb 2018 12:55:43 -0500 From: Konrad Rzeszutek Wilk To: Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org, Radim =?utf-8?B?S3LEjW3DocWZ?= , KarimAllah Ahmed , David Woodhouse , Jim Mattson , Thomas Gleixner , Ingo Molnar , stable@vger.kernel.org Subject: Re: [PATCH 1/3] KVM: x86: use native MSR ops for SPEC_CTRL Message-ID: <20180223175543.GN8252@char.us.oracle.com> References: <1519249297-73718-1-git-send-email-pbonzini@redhat.com> <1519249297-73718-2-git-send-email-pbonzini@redhat.com> <20180222170717.GP31483@char.us.oracle.com> <20180223172220.GK8252@char.us.oracle.com> <7534bcd3-e21b-240c-9ed2-62026ba10301@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7534bcd3-e21b-240c-9ed2-62026ba10301@redhat.com> User-Agent: Mutt/1.8.3 (2017-05-23) X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8813 signatures=668678 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=940 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1802230219 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Fri, Feb 23, 2018 at 06:35:30PM +0100, Paolo Bonzini wrote: > On 23/02/2018 18:22, Konrad Rzeszutek Wilk wrote: > > On Fri, Feb 23, 2018 at 10:37:49AM +0100, Paolo Bonzini wrote: > >> On 22/02/2018 18:07, Konrad Rzeszutek Wilk wrote: > >>>> Having a paravirt indirect call in the IBRS restore path is not a > >>>> good idea, since we are trying to protect from speculative execution > >>>> of bogus indirect branch targets. It is also slower, so use > >>>> native_wrmsrl on the vmentry path too. > >>> But it gets replaced during patching. As in once the machine boots > >>> the assembler changes from: > >>> > >>> callq *0xfffflbah > >>> > >>> to > >>> wrmsr > >>> > >>> ? I don't think you need this patch. > >> > >> Why not be explicit? According to the spec, PRED_CMD and SPEC_CTRL > > > > Explicit is fine. > > > > But I would recommend you change the commit message to say so, and > > perhaps remove 'It is also slower' - as that is incorrect. > > Actually it is faster---that's why I made the change in the first place, > though later I noticed > > > If it is detected to be Xen PV, then yes > > it will be a call to a function. But that won't help as Xen PV runs in > > ring 3, so it has a whole bunch of other issues. > > Ok, I wasn't sure about PVH (which runs in ring 0 afair). Right. PVH is HVM without any emulated devices or BIOSes or such. In the context of the paravirt ops, Xen PVH == Xen HVM. Xen PV (and lguests) are the only ones that patch the the callq *0xffffblah to callq 0xffff800 While everyone else does the wrmsr. > > Paolo