From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-2484469-1519378677-2-8738243361488244099 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no ("Email failed DMARC policy for domain") X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.001, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, 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='utf-8' X-IgnoreVacation: yes ("Email failed DMARC policy for domain") 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=1519378676; b=WKaBC6uu3FcNftH+NrOxUZXFUx2l0l83q3JSb/Lz2Zdl/qv 6MCEf/wLC3nmrVSGrRbZy5us7s+fKIR8j04Yh2LdwkX8yyipLhuuch73ThcDYcQg xaZsPkmsc6jw8dkSrn61dzy2qimgpF8sR5cduqHO8mECQlGADkT06yspwJ0SYGyJ pQDCfBLE+kFz8di0bzbklSybNZ3sJY1cLX7G2i1eX3eTreguw/b9saJU8Sxp67An kw4UlPs9rSCoXw/N+W+V5Atnm2aw+C/iKKTIxqvJHlS6NqDN0evcIhvGz8xvacxm QpEArK+5EvTcON/f3ahvAnJD0z921GOnBvKI6Fg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=subject:to:cc:references:from:message-id :date:mime-version:in-reply-to:content-type :content-transfer-encoding:sender:list-id; s=arctest; t= 1519378676; bh=2oDSnVUIbQ/Q20VhDW7n9VbS+oaZRUBeNBy4/WbEcmM=; b=o RpOTJDEN050gdtHhN4tlRHfsI21yJQOwqUtjf7zpkjjxmR8GFD5yt4PTFPaU5rYM PN7S60KBpS0kVwKSTQV3/zAsmfCMZMs2gQmXLI4AcXnf9jp2liNzY9Xg/zsZQWhG CxNk9YvN79k5Z8lmasrWuv8vKNOlIy+2D2U+aYM3+zkdmnNBaRXIWn+22TyluKoZ LiLztZwrvli343LaFJmcF+kTGsbDn3m1YjnLqhZtgI49pXr52+xv0ToXSU/hv9km YDyOp6WFWA2jYNE6r1NMBwfe2mrnIeUMK2PchdbySsfDma/ez2ES8vMgtWhirf4h 9MLtpw4CfWNHGpPtCEfPw== ARC-Authentication-Results: i=1; mx2.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=fail (p=none,has-list-id=yes,d=none) header.from=redhat.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=redhat.com header.result=pass header_is_org_domain=yes Authentication-Results: mx2.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=fail (p=none,has-list-id=yes,d=none) header.from=redhat.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=redhat.com header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751372AbeBWJhz (ORCPT ); Fri, 23 Feb 2018 04:37:55 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:56960 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751360AbeBWJhy (ORCPT ); Fri, 23 Feb 2018 04:37:54 -0500 Subject: Re: [PATCH 1/3] KVM: x86: use native MSR ops for SPEC_CTRL To: Konrad Rzeszutek Wilk Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org, =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , KarimAllah Ahmed , David Woodhouse , Jim Mattson , Thomas Gleixner , Ingo Molnar , stable@vger.kernel.org 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> From: Paolo Bonzini Message-ID: Date: Fri, 23 Feb 2018 10:37:49 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180222170717.GP31483@char.us.oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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 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 should be passed down to the guest without interception so it's safe to do this. On the other hand, especially with nested virtualization, I don't think you can absolutely guarantee that the paravirt call will be patched to rdmsr/wrmsr. Paolo