From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.91] helo=mail.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Exim 4.30) id 1EZVM0-0002I7-Sv for user-mode-linux-devel@lists.sourceforge.net; Tue, 08 Nov 2005 07:25:44 -0800 Received: from dgate1.fujitsu-siemens.com ([217.115.66.35]) by mail.sourceforge.net with esmtp (Exim 4.44) id 1EZVLx-0003CM-UL for user-mode-linux-devel@lists.sourceforge.net; Tue, 08 Nov 2005 07:25:44 -0800 Message-ID: <4370C36E.2040205@fujitsu-siemens.com> From: Bodo Stroesser MIME-Version: 1.0 Subject: Re: [uml-devel] [PATCH 8/10] UML - Maintain own LDT entries References: <200510310439.j9V4dfbw000872@ccure.user-mode-linux.org> <200511022051.24335.blaisorblade@yahoo.it> <436F469B.3080607@fujitsu-siemens.com> <200511072028.23111.blaisorblade@yahoo.it> In-Reply-To: <200511072028.23111.blaisorblade@yahoo.it> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: user-mode-linux-devel-admin@lists.sourceforge.net Errors-To: user-mode-linux-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: The user-mode Linux development list List-Post: List-Help: List-Subscribe: , List-Archive: Date: Tue, 08 Nov 2005 16:25:34 +0100 To: Blaisorblade Cc: user-mode-linux-devel@lists.sourceforge.net, Jeff Dike , linux-kernel@vger.kernel.org, Allan Graves Blaisorblade wrote: > On Monday 07 November 2005 13:20, Bodo Stroesser wrote: > >>Blaisorblade wrote: >> >>>On Monday 31 October 2005 05:39, Jeff Dike wrote: >>> >>>>From: Bodo Stroesser > > >>>Or at least so I think (I must still give a proper look afterwards, and >>>I'll post patches). Actually it seems that this is done on purpose, but I >>>don't agree too much on this. I will see. > > >> From the beginning my new code for SKAS included the checks/buffering you >>later inserted for TT and SKAS. So this patch is a second version adapted >>to your changes. It shifts your improvements into TT path only (where I >>didn't do any changes in my old patch), while it uses my own stuff for >>SKAS. Thus the patch doesn't really revert your improvements, but restricts >>it to TT. As in SKAS0 UML now holds its own LDT data, there is no need for >>buffering in this case. So I think it makes sense to have separate code for >>SKAS. > > Yep, ok - I'm undecided about the new code for SKAS3, but it may make sense > (i.e. no opinion). > > Instead, I have another question: is there a proper reason for using the > processor format for storing the info and translating it back to (struct > user_desc)? I am planning to avoid this double translation because I don't > like it. Any opinion? In my opinion there is no reason to change the current implementation for SAKS3/0. Note: if someone reads LDT via [sys_]modify_ldt(), he will receive the requested data in "processor format", that is LDT-descriptors. He will receive a list of descriptors starting at the first descriptor of the LDT, thus no entry number is needed in the enties. The only case that uses user_desc is when writing one desriptor via modify_ldt(). modify_ldt(WRITE) exactly writes one LDT-descriptor, so user_desc must contain the number of the entry to write. Thus user_desc is bigger than LDT descriptor. It also uses an other data layout resulting in double the size of LDT-descriptor. So I think it doesn't make sense to store user_desc. We save memory storing the resulting LDT-descriptors, which then are copied transparently on modify_ldt(READ). Conversion between user_desc and LDT-entry is done on modify_ldt(WRITE) in SKAS0 only. No other conversions are done in UML. Bodo ------------------------------------------------------- SF.Net email is sponsored by: Tame your development challenges with Apache's Geronimo App Server. Download it for free - -and be entered to win a 42" plasma tv or your very own Sony(tm)PSP. Click here to play: http://sourceforge.net/geronimo.php _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel