Received: by 2002:a05:6a10:2785:0:0:0:0 with SMTP id ia5csp646720pxb; Thu, 14 Jan 2021 15:11:19 -0800 (PST) X-Google-Smtp-Source: ABdhPJz5fW0mGs09Diu0eINfo0h8DtiGZJJxjiyja6yMrWCMyyRHPW+n425Iyuo3U6pQpdM6imq1 X-Received: by 2002:a17:906:c349:: with SMTP id ci9mr5650341ejb.198.1610665879439; Thu, 14 Jan 2021 15:11:19 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1610665879; cv=none; d=google.com; s=arc-20160816; b=E+kp2f5gkRw3ZeQJnqTi7y40pH7guVe6Qn9q0QqYDOhhBl776Zz0aPDDqyNltOrfAH UWAs3iUl54jdt6FTEhkPPpsbDMcgEXrFFNnn7XN1gLPgzJq42gGgJyr5EgxVr3upsd4k po9vVj/dvIUT1CBUk94j7vkgeVVGfDeeHy9xiPTvPd6QxcwWzSC6bX0bg/SOfTbbWPoz 2teCO6/hF4dNe/7at3wXufEqMB+EiH0u+a43+MEg9TnS2EIWURuomc8ymUFOLV0Z9wk/ vc7blIDCg2zZN/L99xUfYG0qS17uFnwlQw3RREmUiQSyeiCo/+sMP2u13xtzPF3xIbF2 Ibjg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:cc:to:subject:message-id:date:from:in-reply-to :references:mime-version:dkim-signature; bh=VLCIXId9Ur9EEU+g0ZhcxPqlBXoFwGkEQByEAfvt7pM=; b=Vjw7DlyeZba/O+fgbDKX9rbW8fM0OFSYS1GVCohdAV9+o1I4vz4fdf05Mz94US/YfH sv/FYqmCQlHE3btyxMM9zwHcKMYObiXH2jOHY37u5jloPp9jQ026TW0cgEe1MOCcWEHE MnK5Lm0WxUzOR3R0pwx7j/JyKaoTKkbIa1Lf2mZLTff3eBTYF3t7CqDeksWt8269m1QP 0NUyEBwuRMKUFdJq17uRPo5ulN1IGc4cRLKgTjU//64QqS3dSD+LOsqVYEnj00gYBBnJ VjWw4sbWWaDP4crCfqusnQM4PptEk76IPpYiFPAcBilGp90qUpG/1ZyDuxFUzNJl3bcS Xbkw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=vcqi2AFN; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id ce12si3487396edb.604.2021.01.14.15.10.55; Thu, 14 Jan 2021 15:11:19 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=vcqi2AFN; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730885AbhANXKS (ORCPT + 99 others); Thu, 14 Jan 2021 18:10:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36250 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730840AbhANXKS (ORCPT ); Thu, 14 Jan 2021 18:10:18 -0500 Received: from mail-ej1-x62c.google.com (mail-ej1-x62c.google.com [IPv6:2a00:1450:4864:20::62c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 71F20C061757; Thu, 14 Jan 2021 15:09:37 -0800 (PST) Received: by mail-ej1-x62c.google.com with SMTP id ga15so10708240ejb.4; Thu, 14 Jan 2021 15:09:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=VLCIXId9Ur9EEU+g0ZhcxPqlBXoFwGkEQByEAfvt7pM=; b=vcqi2AFNMuHivlPqf62balXOKuMVUeY1LDDZ4fmw8Hnj3tSgqsyBXm7JbDJF9WlPPY 8bJIm6Ttru3yi691agA+flqNijZxjZb73DiVbR3W1rDlicn5SY0T/u1wnGLhVdhlhusq iUDZ9zEiHaVMoNHxfKYLw2zfMNEvElIMBgtsFc0UubmiNgcefy6G100CRGjkC/Onmh7E CjaXGFSpX5neYOuFEg9uZCFcuk5tlNK3ZFh7zBff8qbLnavJLnhaCot0fn+g7eT1+kDi OBkCWhRl94dCP59/v7lWm1x+W8Jhv/AloiQ2A0eS0Kn6dxP02VJmvd7nNTv1Jp6G4AgO AkuQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=VLCIXId9Ur9EEU+g0ZhcxPqlBXoFwGkEQByEAfvt7pM=; b=QdZcfff9KM2PSbbHQjbzwU43s33sINhOIBmWsG57aRdfCz2V9Fhdpthr/jIGFHv5it cxTOXbB19Tjgo4O+KmPxlIzuiKlnKp/gVj6HVt4q2eN0gIYTMAPSMf4GoEHbkuBVgmfe KulGRqKZ/NwURryRdOWECyQmlrSHs/6CUW7d6/cCMTErwYtuUWkfIwUIPDhpkgpfXQuA Ka8l0uAIX2NhhMKsqKHdTa3cgrAyQb5eL4DK4FROXQf0T4dVu9fSxJO6eyTBZPX9Nb9Z hIH57yxQlt+mzg7t+DX8JH7cXGoLVnoy5igBdncW469DV5ZUZojlRwe2/EPJKg8PwHdb 1tPA== X-Gm-Message-State: AOAM53293loUf7/G4wPFzZtz3F9M6nQ5S70Es/p8i9jEBndIFPzV5zdy RZqfEvCiW5W4VpkvM98Em9W+NE/lCwM0Osgked9k5l8IEFU= X-Received: by 2002:a17:906:22c7:: with SMTP id q7mr6812484eja.486.1610665776265; Thu, 14 Jan 2021 15:09:36 -0800 (PST) MIME-Version: 1.0 References: <1be37673-db0e-f09d-68c8-f929be4019ab@physik.fu-berlin.de> In-Reply-To: From: Max Filippov Date: Thu, 14 Jan 2021 15:09:24 -0800 Message-ID: Subject: Re: Old platforms: bring out your dead To: Arnd Bergmann Cc: John Paul Adrian Glaubitz , Linus Walleij , Gerhard Pircher , Arnd Bergmann , Linux Kernel Mailing List , linux-m68k , Sparc kernel list , Linux-sh list Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Arnd, On Thu, Jan 14, 2021 at 1:25 PM Arnd Bergmann wrote: > | arch/mips/Kconfig:config HIGHMEM > | arch/xtensa/Kconfig:config HIGHMEM > > AFAICT On MIPS (prior to MIPS32r3) and xtensa, you have at > most 512MB in the linear map, so the VMSPLIT_2G or VMSPLIT_4G_4G > tricks won't work. Regarding xtensa this was done to minimize difference between MMUv2 and MMUv3 virtual memory layouts. MMUv2 has been obsoleted more than 10 years ago, and MMUv3 is much more flexible and can do e.g. 4GB linear map. The only piece of xtensa MMUv2 hardware that I have has 96MB of DRAM which fits into its linear mapping. So maybe it's time to do a cleanup and rearrange virtual memory layout to eliminate the need of highmem. > I have no idea who uses xtensa systems with lots of memory on > modern kernels. We definitely use it for development internally at Cadence/Tensilica, mainly on simulators, but also on FPGA boards (e.g. on KC705 we can use all of the 1GB onboard DRAM). In the last few years we've had a few support requests for linux on xtensa cores with MMU, but AFAICT none of them had to deal with more than 512MB of onboard memory. -- Thanks. -- Max