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=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 52E87C433E0 for ; Mon, 13 Jul 2020 13:07:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2447D20738 for ; Mon, 13 Jul 2020 13:07:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="M5uPLARN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729736AbgGMNH6 (ORCPT ); Mon, 13 Jul 2020 09:07:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45208 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729523AbgGMNH4 (ORCPT ); Mon, 13 Jul 2020 09:07:56 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5913FC061755 for ; Mon, 13 Jul 2020 06:07:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=OqcpgdOdGZwi6J+uiLg6n6Rw5mDd47NeVWUGd6LWGdM=; b=M5uPLARN24iL+ApD0GZi56Vlc5 Dty5/OdSlJsVN1jTIxk4HQKJcGhGAwSgX07MSHpP47Nv7DlaTsbWyKf3gzYEeCAwF1vbcZkuJfGdc f52z2EO3vdO+OwPRfr2ozmWZc5NJ/ZrbF+jnXj10Jz90RfTaECMWPg8XFOuX/sfllFaQgRiRIDjZS 6V4JbqvNpNzaH7aPXz2UgJ5LeqHuZ+ZvchIw72KSHDzStVqlaaxgK3jACmrFmrwmwjPl4siGjHH9x YCACeU6TrwZh5N6FncIFiQbO6BM62nmCh8pkBhSRaEu64gnTWoMolXtgUIb/7t9isChq1DT29vM1c aLYz6yZw==; Received: from hch by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1juyAC-0000PB-3U; Mon, 13 Jul 2020 13:06:32 +0000 Date: Mon, 13 Jul 2020 14:06:32 +0100 From: Christoph Hellwig To: Palmer Dabbelt Cc: mick@ics.forth.gr, mark.rutland@arm.com, gregory.0xf0@gmail.com, peterz@infradead.org, catalin.marinas@arm.com, linus.walleij@linaro.org, Palmer Dabbelt , brendanhiggins@google.com, elver@google.com, glider@google.com, krzk@kernel.org, mchehab+samsung@kernel.org, will@kernel.org, mingo@kernel.org, uwe@kleine-koenig.org, takahiro.akashi@linaro.org, paulmck@kernel.org, masahiroy@kernel.org, linux@armlinux.org.uk, willy@infradead.org, rppt@linux.ibm.com, bgolaszewski@baylibre.com, kernel-team@android.com, pmladek@suse.com, zaslonko@linux.ibm.com, keescook@chromium.org, Arnd Bergmann , broonie@kernel.org, matti.vaittinen@fi.rohmeurope.com, ben-linux@fluff.org, dan.j.williams@intel.com, linux-arm-kernel@lists.infradead.org, davidgow@google.com, rdunlap@infradead.org, Nick Desaulniers , linux-kernel@vger.kernel.org, mhiramat@kernel.org, ardb@kernel.org, akpm@linux-foundation.org, davem@davemloft.net Subject: Re: [PATCH 1/3] lib: Add a generic copy_oldmem_page() Message-ID: <20200713130632.GA29945@infradead.org> References: <20200711035544.2832154-1-palmer@dabbelt.com> <20200711035544.2832154-2-palmer@dabbelt.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200711035544.2832154-2-palmer@dabbelt.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 10, 2020 at 08:55:42PM -0700, Palmer Dabbelt wrote: > +ssize_t copy_oldmem_page(unsigned long pfn, char *buf, > + size_t csize, unsigned long offset, > + int userbuf) > +{ > + void *vaddr; > + > + if (!csize) > + return 0; > + > + vaddr = memremap(__pfn_to_phys(pfn), PAGE_SIZE, MEMREMAP_WB); > + if (!vaddr) > + return -ENOMEM; Doing a memremap for every page is very inefficient. Also I don't see why you'd want to even do that. All memory is in the direct mapping for RISC-V. For other architecture that support highmem kmap_atomic_pfn would do the job, which is what I'd use in a generic version.