From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752707AbbCYAOZ (ORCPT ); Tue, 24 Mar 2015 20:14:25 -0400 Received: from mga14.intel.com ([192.55.52.115]:42370 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751899AbbCYAOW (ORCPT ); Tue, 24 Mar 2015 20:14:22 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.11,461,1422950400"; d="scan'208";a="545817537" Date: Tue, 24 Mar 2015 17:14:16 -0700 From: Jim Kukunas To: Ingo Molnar Cc: Linux Kernel , tom.zanussi@linux.intel.com, Arjan van de Ven , "H. Peter Anvin" , tglx@linutronix.de, mingo@redhat.com, x86@kernel.org Subject: Re: [RFC] x86 XIP Message-ID: <20150325001416.GA2600@jtk-ivb.jf.intel.com> Mail-Followup-To: Ingo Molnar , Linux Kernel , tom.zanussi@linux.intel.com, Arjan van de Ven , "H. Peter Anvin" , tglx@linutronix.de, mingo@redhat.com, x86@kernel.org References: <1427096800-30452-1-git-send-email-james.t.kukunas@linux.intel.com> <20150323080713.GB25620@gmail.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="ZPt4rx8FFjLCG7dd" Content-Disposition: inline In-Reply-To: <20150323080713.GB25620@gmail.com> User-Agent: Mutt/1.5.20 (2009-12-10) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --ZPt4rx8FFjLCG7dd Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Mar 23, 2015 at 09:07:14AM +0100, Ingo Molnar wrote: > * Jim Kukunas wrote: >=20 > >=20 > > Hi Folks, > >=20 > > This patchset introduces eXecute-In-Place (XIP) support for x86.=20 > > [...] >=20 > So we'd need a lot better high level description than this: In future patch revisions, I'll update my coverletter to include the information below. > - a bit of background description: what are the advantages of having > the kernel image in non-RAM (flash), etc. Currently for tiny memory-constrained embedded systems, the kernel configuration is usually stripped down in order to reduce the kernel's=20 RAM footprint, freeing up more precious memory for user space and allowing the kernel to fit into smaller systems. With XIP, the kernel's text and read-only data sections are never loaded into RAM, thereby reducing the kernel's memory usage. Also, since a significant portion of the kernel is never loaded into RAM, a larger kernel configuration can be used without bloating memory usage. I haven't done any performance analysis yet, but it's probably safe to say that executing from storage will negatively affect performance. > - on what hardware/bootloaders is or will be XIP supported? With regards to supported hardware, these patches aren't targeting any specific platform. As mentioned in the coverletter, there are current limits on the supported configurations (32-bit only, no SMP, no PAE), but these are not technical limits ... I just need to implement support for them. With regards to supported bootloaders, I've been testing with a small bootloader that I wrote specifically for XIP. Which other bootloaders I add support to will depend on the feedback/requests that I get. > Also, there should probably be some fail-safe mechanism included: such > as to check whether caching attributes (MTRRs, PAT) are properly set=20 > for the XIP area (at minimum to not be uncacheable). Good idea. I'll add that into the next revision. Thanks. --=20 Jim Kukunas Intel Open Source Technology Center --ZPt4rx8FFjLCG7dd Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.14 (GNU/Linux) iQIcBAEBAgAGBQJVEf3YAAoJEJsd5ffp0QqMQWgP/0ewPYIS422uxW3AWTrdzQha VJ3UzNSMPqaLiyicf2l1kZzvBKsBo2a0wQsH207/4enHLytZzSm6x6HwtR6CRUEJ DyEne2Kg1urZoWRSm6iC2fUmdKhb6cCiA8iOvJcNFhHs7pB4Ck/u5x8SM8b5I5ju 6Ef2ipHBfZqirGQx+QrDfihgENUOtHeR6o4I/GMBJiNZCLJpGmfSmq7WimkmlvdI dTWbx+TZZiZZTPupsLF4qO08AP+IhuEMrrKlWurG5y2nsqQQ4RH/fBqd3Z+RRFFf yLv8JGY/B2om1OdvvRBcLPNtDhUq+RXc+06OLY3RDmJLn0fdfk/N4KNuMDHm5emH ujPSrKYyZzYKEqxUZE6l1T3PHK1ZHzUqXP5CZGIY8UiBGxV/QPBJruNhdcSSO5S0 qml7p/X2SyFEMFXPrFSJn1KsEvwhL+tTDAzSYbAzHBCEoy2e2jZH+nNlwFWwEcey qq1H64QQCBVmAd4OAgQbzXCO6sitml98Hhv8aDsroBCfeLUNy+gq3c17fy90Lr5s ja6ZOw7RHJfPwTfCXVDWHWoQYfXo7oFQJymTh6xCKL72Qw5zKxOnjbVF7BbJfWWE D3k93bmNdC78igUcIR0+Ip2bUPA9JcVSqeEXldAuSd0W8niCJEBtxdSJCBUAB5za 0CHQ48DOB/9Ovtzi7RUr =JLYq -----END PGP SIGNATURE----- --ZPt4rx8FFjLCG7dd--