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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED autolearn=ham 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 88C69C43381 for ; Fri, 22 Feb 2019 10:21:51 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 57D1F20823 for ; Fri, 22 Feb 2019 10:21:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="S1nPMhme" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 57D1F20823 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:From:References:To:Subject:Reply-To:Content-ID:Content-Description :Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=jwGgcvEGJflrlG3Ag5PPMrn5ALJ1Yhzidr9CHPAoKP0=; b=S1nPMhmetBMSsJ /K50acOkozFQ8mSjSL8rluw3qwDa90k1zHO6T98yw33seD/xdcj7/pXyKdAYaFRC+A5PYJ0nySPu7 CtohBFMoLV2nBMXIFX43OqUn/UJXCiznOEvYGT1GZQwss2v0/ctByWh6JQg1rNYeFLRcZBEWf2WSZ Xyqnxg6Nk1UycbK2u77SedAzca9geyGFttqLI+CFBs+yBU8CR/RywLtRENaXzGrfYQ1KLp8nfwUC3 eZv29zX6TXBPwA1WQF7yXSH7xoDsl2/hRADa5YO7CGRvy+eHjvDCaHpOeE7E9fGUAcm0WpBfS0OBI KOMwrJwj0g1SX/ZNqBzA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gx7xk-0003jl-GF; Fri, 22 Feb 2019 10:21:48 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gx7xh-0003jL-FH for linux-arm-kernel@lists.infradead.org; Fri, 22 Feb 2019 10:21:46 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C24EB80D; Fri, 22 Feb 2019 02:21:44 -0800 (PST) Received: from [10.1.196.69] (e112269-lin.cambridge.arm.com [10.1.196.69]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A30923F703; Fri, 22 Feb 2019 02:21:41 -0800 (PST) Subject: Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros To: "Kirill A. Shutemov" References: <20190221113502.54153-1-steven.price@arm.com> <20190221113502.54153-4-steven.price@arm.com> <20190221142812.oa53lfnnfmsuh6ys@kshutemo-mobl1> <20190221145706.zqwfdoyiirn3lc7y@kshutemo-mobl1> <20190221210618.voyfs5cnafpvgedh@kshutemo-mobl1> From: Steven Price Message-ID: <9441949b-6982-eea3-a05e-e277776ff821@arm.com> Date: Fri, 22 Feb 2019 10:21:40 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.0 MIME-Version: 1.0 In-Reply-To: <20190221210618.voyfs5cnafpvgedh@kshutemo-mobl1> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190222_022145_513968_F6247ADD X-CRM114-Status: GOOD ( 17.33 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Dave Hansen , Arnd Bergmann , Ard Biesheuvel , Peter Zijlstra , Catalin Marinas , x86@kernel.org, Will Deacon , linux-kernel@vger.kernel.org, linux-mm@kvack.org, =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Ingo Molnar , Borislav Petkov , Andy Lutomirski , "H. Peter Anvin" , James Morse , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, "Liang, Kan" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 21/02/2019 21:06, Kirill A. Shutemov wrote: > On Thu, Feb 21, 2019 at 05:16:46PM +0000, Steven Price wrote: >>>> Note that in terms of the new page walking code, these new defines are >>>> only used when walking a page table without a VMA (which isn't currently >>>> done), so architectures which don't use p?d_large currently will work >>>> fine with the generic versions. They only need to provide meaningful >>>> definitions when switching to use the walk-without-a-VMA functionality. >>> >>> How other architectures would know that they need to provide the helpers >>> to get walk-without-a-VMA functionality? This looks very fragile to me. >> >> Yes, you've got a good point there. This would apply to the p?d_large >> macros as well - any arch which (inadvertently) uses the generic version >> is likely to be fragile/broken. >> >> I think probably the best option here is to scrap the generic versions >> altogether and simply introduce a ARCH_HAS_PXD_LARGE config option which >> would enable the new functionality to those arches that opt-in. Do you >> think this would be less fragile? > > These helpers are useful beyond pagewalker. > > Can we actually do some grinding and make *all* archs to provide correct > helpers? Yes, it's tedious, but not that bad. > > I think we could provide generic helpers for folded levels in > and rest has to be provided by the arch. > Architectures that support only 2 level paging would need to provide > pgd_large(), with 3 -- pmd_large() and so on. Fair enough, I'll have a go and hopefully people will be able to correct it if I make any mistakes - I'm certainly not going to be able to test all architectures myself. Steve _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel