From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B3E7AC43466 for ; Sun, 20 Sep 2020 08:56:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3A2B1214F1 for ; Sun, 20 Sep 2020 08:56:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b="BD5pR74U" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726273AbgITI4M (ORCPT ); Sun, 20 Sep 2020 04:56:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52292 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726250AbgITI4M (ORCPT ); Sun, 20 Sep 2020 04:56:12 -0400 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [IPv6:2001:4d48:ad52:32c8:5054:ff:fe00:142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 93651C061755 for ; Sun, 20 Sep 2020 01:56:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=rlQ8rLBagPRAbeKX8ARZvw0EpRyUF+JYIjrToj2vLsc=; b=BD5pR74Uvt//oVFqGedXec1Wu UALVxT4WRpBTYVH6TjW7jlUgVenrBFP4WS5+4hA1CyUczD9EJQyxc/LvTYuuP9dgDIwvJPvblG3wT kigBsy+e6YgjiQkYah1CC2OnGUl+yyXyeePlFqFBID1l/behwpcg+4Nfny+5o4NQD4pxpIjqEwQgB Q7/UAIuKViFuXHgrzm7zll3tie7TZRuJMykZ/u5PbT1eKbkb9va4bft+6SipFBbsuAaqWD89NJGiN VSClKWAw3PpLRtxIx230mYlo6Trjwn/YVotAzwYMzGfVvg9J33C2Hk5xbiLNhspS46EVlIdmfVCI4 r9m6AED1A==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:35966) by pandora.armlinux.org.uk with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1kJv8Y-0000TM-MW; Sun, 20 Sep 2020 09:55:59 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1kJv8U-0000BR-1r; Sun, 20 Sep 2020 09:55:54 +0100 Date: Sun, 20 Sep 2020 09:55:54 +0100 From: Russell King - ARM Linux admin To: Nicolas Pitre Cc: Ard Biesheuvel , linux-arm-kernel@lists.infradead.org, linux-efi@vger.kernel.org, Zhen Lei , Santosh Shilimkar , Linus Walleij Subject: Re: [RFC/RFT PATCH 0/6] ARM: p2v: reduce min alignment to 2 MiB Message-ID: <20200920085553.GW1551@shell.armlinux.org.uk> References: <20200918103102.18107-1-ardb@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: Russell King - ARM Linux admin Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org On Sat, Sep 19, 2020 at 07:49:26PM -0400, Nicolas Pitre wrote: > On Fri, 18 Sep 2020, Ard Biesheuvel wrote: > > This series is inspired by Zhei Len's series [0], which updates the > > ARM p2v patching code to optionally support p2v relative alignments > > of as little as 64 KiB. > > > > Reducing this alignment is necessary for some specific Huawei boards, > > but given that reducing this minimum alignment will make the boot > > sequence more robust for all platforms, especially EFI boot, which > > no longer relies on the 128 MB masking of the decompressor load address, > > but uses firmware memory allocation routines to find a suitable spot > > for the decompressed kernel. > > > > This series is not based on Zhei Len's code, but addresses the same > > problem, and takes some feedback given in the review into account: > > - use of a MOVW instruction to avoid two adds/adcs sequences when dealing > > with the carry on LPAE > > - add support for Thumb2 kernels as well > > - make the change unconditional - it will bit rot otherwise, and has value > > for other platforms as well. > > > > The first four patches are general cleanup and preparatory changes. > > Patch #5 implements the switch to a MOVW instruction without changing > > the minimum alignment. > > Patch #6 reduces the minimum alignment to 2 MiB. > > > > Tested on QEMU in ARM/!LPAE, ARM/LPAE, Thumb2/!LPAE and Thumb2/LPAE modes. > > At this point I think this really ought to be split into a file of its > own... and maybe even rewritten in C. Even though I wrote the original > code, I no longer understand it without re-investing time into it. But > in either cases the whole of head.S would need to have its registers > shuffled first to move long lived values away from r0-r3,ip,lr to allow > for standard function calls. However, that code has to run _before_ the virtual mappings are setup, which makes C code out of the question, unless we build a separate executable binary and then insert it into the kernel image. So, sorry, it's not going to be practical to rewrite it in C. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!