From owner-freebsd-hackers@FreeBSD.ORG Sat May 17 17:53:23 2008 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 6F926106564A for ; Sat, 17 May 2008 17:53:23 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from relay03.kiev.sovam.com (relay03.kiev.sovam.com [62.64.120.201]) by mx1.freebsd.org (Postfix) with ESMTP id 026918FC15 for ; Sat, 17 May 2008 17:53:22 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from [212.82.216.226] (helo=skuns.kiev.zoral.com.ua) by relay03.kiev.sovam.com with esmtps (TLSv1:AES256-SHA:256) (Exim 4.67) (envelope-from ) id 1JxQav-00043Z-Kf; Sat, 17 May 2008 20:53:21 +0300 Received: from deviant.kiev.zoral.com.ua (root@deviant.kiev.zoral.com.ua [10.1.1.148]) by skuns.kiev.zoral.com.ua (8.14.2/8.14.2) with ESMTP id m4HHrEId083294 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Sat, 17 May 2008 20:53:14 +0300 (EEST) (envelope-from kostikbel@gmail.com) Received: from deviant.kiev.zoral.com.ua (kostik@localhost [127.0.0.1]) by deviant.kiev.zoral.com.ua (8.14.2/8.14.2) with ESMTP id m4HHrCni089181; Sat, 17 May 2008 20:53:12 +0300 (EEST) (envelope-from kostikbel@gmail.com) Received: (from kostik@localhost) by deviant.kiev.zoral.com.ua (8.14.2/8.14.2/Submit) id m4HHrCXA089180; Sat, 17 May 2008 20:53:12 +0300 (EEST) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: deviant.kiev.zoral.com.ua: kostik set sender to kostikbel@gmail.com using -f Date: Sat, 17 May 2008 20:53:12 +0300 From: Kostik Belousov To: Rui Paulo Message-ID: <20080517175312.GM18958@deviant.kiev.zoral.com.ua> References: <482E93C0.4070802@icyb.net.ua> <482EFBA0.30107@FreeBSD.org> <482F1191.70709@icyb.net.ua> <482F1529.5080409@FreeBSD.org> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="jva9z9iU4vGix/sz" Content-Disposition: inline In-Reply-To: <482F1529.5080409@FreeBSD.org> User-Agent: Mutt/1.4.2.3i X-Virus-Scanned: ClamAV version 0.91.2, clamav-milter version 0.91.2 on skuns.kiev.zoral.com.ua X-Virus-Status: Clean X-Spam-Status: No, score=-4.4 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=ham version=3.2.4 X-Spam-Checker-Version: SpamAssassin 3.2.4 (2008-01-01) on skuns.kiev.zoral.com.ua X-Scanner-Signature: fa718887f43e9e3967a9d10f43843ba4 X-DrWeb-checked: yes X-SpamTest-Envelope-From: kostikbel@gmail.com X-SpamTest-Group-ID: 00000000 X-SpamTest-Header: Not Detected X-SpamTest-Info: Profiles 2835 [May 13 2008] X-SpamTest-Info: helo_type=3 X-SpamTest-Method: none X-SpamTest-Rate: 0 X-SpamTest-Status: Not detected X-SpamTest-Status-Extended: not_detected X-SpamTest-Version: SMTP-Filter Version 3.0.0 [0278], KAS30/Release Cc: freebsd-hackers@freebsd.org, Andriy Gapon Subject: Re: rdmsr from userspace X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 17 May 2008 17:53:23 -0000 --jva9z9iU4vGix/sz Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sat, May 17, 2008 at 06:26:01PM +0100, Rui Paulo wrote: > Andriy Gapon wrote: > >on 17/05/2008 18:37 Rui Paulo said the following: > >>Andriy Gapon wrote: > >>> > >>>It seems that rdmsr instruction can be executed only at the highest=20 > >>>privilege level and thus is not permitted from userland. Maybe we=20 > >>>should provide something like Linux /dev/cpu/msr? > >>>I don't like interface of that device, I think that ioctl approach=20 > >>>would be preferable in this case. > >>>Something like create /dev/cpuN and allow some ioctls on it:=20 > >>>ioctl(cpu_fd, CPU_RDMSR, arg). > >>>What do you think? > >>> > >> > >>While I think this (devcpu) is good for testing and development, I=20 > >>prefer having a device driver to handle that specific MSR than a=20 > >>generic /dev/cpuN where you can issue MSRs. > >>Both for security and reliability reasons. > > > >What about /dev/pci, /dev/io? Aren't they a precedent? >=20 > They are, but, IMHO, we should no longer continue to create this type of= =20 > interfaces. Why ? Are developers some kind of the second-class users ? I would have no opinion on providing /dev/cpu by the loadable module, not compiled into GENERIC. But the interface itself is useful at least for three things: - CPU identification (see x86info or whatever it is called); - CPU tweaking for bugs workaround without patching the kernel; - updating the CPU microcode. None of these is limited to the developers only. I am interested why Stanislav still did not submitted it for inclusion into the base still. Maybe, some other reasons exist. --jva9z9iU4vGix/sz Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iEYEARECAAYFAkgvG4gACgkQC3+MBN1Mb4iodgCcCKViPJjwM7qHV/sFSDZOK/zS OQkAoN6vNYhb9CltjRgoBAU3fkNyP4Rt =1Z2a -----END PGP SIGNATURE----- --jva9z9iU4vGix/sz--