From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752359AbdK2SLr (ORCPT ); Wed, 29 Nov 2017 13:11:47 -0500 Received: from mga04.intel.com ([192.55.52.120]:64203 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750816AbdK2SLo (ORCPT ); Wed, 29 Nov 2017 13:11:44 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.45,338,1508828400"; d="scan'208";a="11089993" Date: Wed, 29 Nov 2017 20:02:32 +0200 From: Jarkko Sakkinen To: platform-driver-x86@vger.kernel.org, x86@kernel.org Cc: linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Darren Hart , Andy Shevchenko Subject: Re: [PATCH v6 06/11] intel_sgx: driver for Intel Software Guard Extensions Message-ID: <20171129180232.h3f2fbqocfj32tg7@linux.intel.com> References: <20171125193132.24321-1-jarkko.sakkinen@linux.intel.com> <20171125193132.24321-7-jarkko.sakkinen@linux.intel.com> <20171126173356.ik7dhvvcojgermof@linux.intel.com> <20171126184627.hegr3qzgous5ivpe@linux.intel.com> <20171126190109.qfvjoq2sbz5x3ve7@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171126190109.qfvjoq2sbz5x3ve7@linux.intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Nov 26, 2017 at 09:01:09PM +0200, Jarkko Sakkinen wrote: > On Sun, Nov 26, 2017 at 08:46:27PM +0200, Jarkko Sakkinen wrote: > > On Sun, Nov 26, 2017 at 07:33:56PM +0200, Jarkko Sakkinen wrote: > > > > +struct sgx_encl_page { > > > > + unsigned long addr; > > > > + unsigned int flags; > > > > + void *epc_page; > > > > + struct sgx_va_page *va_page; > > > > + unsigned int va_offset; > > > > + struct list_head list; > > > > +}; > > > > > > This can be without major streches hoops packed way more. There are 12 > > > bits free for use in the addr field. I can use low three bits for flags > > > and upper nine bits for va_offset. > > > > > > I think I can also quite easily union epc_page and va_page fields. > > > > > > With these changes the struct would shrink to: > > > > > > struct sgx_encl_page { > > > unsigned long addr; > > > union { > > > void *epc_page; > > > struct sgx_va_page *va_page; > > > }; > > > struct list_head list; > > > }; > > > > Once I started to thinking more about this I realized that this can be > > shrunk even further. I can drop the list field and use a tag for loaded > > pages in the radix tree where these are stored. The end result would be > > > > struct sgx_encl_page { > > unsigned long addr; > > union { > > void *epc_page; > > struct sgx_va_page *va_page; > > }; > > }; > > With this last size optimization there is an issue that it would be nice > to select the pages to be swapped out in FIFO order. That kind of means > that tag would not work quite well. > > I could try an approach where I have a pointer array to present a queue > inside struct sgx_encl for loaded pages and in that way get rid of the > 'list' field. I did other optimizations except taking the list field away so it's now a 32 byte structure. I guess sufficient for the first mainline version. /Jarkko