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=-3.6 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 8E54AC433ED for ; Wed, 21 Apr 2021 11:06:58 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 1C2F961422 for ; Wed, 21 Apr 2021 11:06:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1C2F961422 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:35712 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lZAh7-0000By-6W for qemu-devel@archiver.kernel.org; Wed, 21 Apr 2021 07:06:57 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:34066) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lZAgL-0007j3-PG for qemu-devel@nongnu.org; Wed, 21 Apr 2021 07:06:09 -0400 Received: from mail-ej1-x629.google.com ([2a00:1450:4864:20::629]:40801) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1lZAgH-0003AW-Ev for qemu-devel@nongnu.org; Wed, 21 Apr 2021 07:06:09 -0400 Received: by mail-ej1-x629.google.com with SMTP id n2so62866485ejy.7 for ; Wed, 21 Apr 2021 04:06:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=TxWuQZKRedPJGYp27hbOmtzPUrXJyfjU9m/ETwoBG14=; b=xjONI/8BzNLz+6KlIaCJSKP8/9w4+4S3mmcD9WvPasdwS8YnAVcwetmgNCo5K5nbpr jSQhU1SAUapsVdgiDcRiohF8LdZvLV8FrP0/HHwsB0foZOCB+HOix5OyilGVxkwEvCvs b8sP+HhSEQNGnBWilmSeDwFMUGkbV5RPku22NWOu+pBvQJ/FjygjSVmpMWq1+GX2OPf6 jz2AhpR44hTQQdd+lQWgmyyq4UVqbJlU+5JByAwfSjKiiAqcI4lGyEghgRpNRKkjRQwz Q9T5MdJkWK+WwgIkU6Vim21VJC/59ei7cc4Ee3ayspqx5lW9k6AkHjYjKpaqBs4VZywW qKwQ== 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=TxWuQZKRedPJGYp27hbOmtzPUrXJyfjU9m/ETwoBG14=; b=H7UxWyHe6KJcqdMlKVcdkRv6BYEVMrHl6iKO/W2fn/tAwVZyAyjV3I5XISAQOrdZV5 UGyi3UFm+1uCcnMUeu5G/UtMVFaHCov9TctXMSkqcQYNAzYJ7iaLTe8fZldwfPv3tJsL YKgQ8Fvm/wBpfCVe3sdvut65fe5y1+DcZwPhs1lxfYFVnWyQF0SmDhqwaZupyZswNxNJ M7mIofkheUGAFV84Jw68hREy9IqdmGi9R0FgS9W0mpGx/I9N0UegQNGt5FaupQUdOZwN A7Mu74qwrFNP9OYEr0H8VJ+F1QoGzqFcU1jrHDE3rW8j7cZsiiayFVfOEkSbW9t0DvB0 2Mag== X-Gm-Message-State: AOAM5329MePbjBjvfT96JTIyPBOJaGTUDcJZ7RFF3xboFwhkr9MKeomt EZqkh2SfniowUcT8T8w3jIRgHFsE5f148B+G0FCeCw== X-Google-Smtp-Source: ABdhPJzfvQ0GybjK2hWhEgocOQbbDagd7WlGI6E6K1YpQ9niSwXtP/n58us36jQ2EOOL82FVayOSJh0fGAJrLuDX9ec= X-Received: by 2002:a17:906:6d41:: with SMTP id a1mr25217904ejt.482.1619003161430; Wed, 21 Apr 2021 04:06:01 -0700 (PDT) MIME-Version: 1.0 References: <20210417140206.673885-1-f4bug@amsat.org> <8f59bd60-3588-3be0-c44c-1ebfbefd78bd@ilande.co.uk> <67955dd0-dfc7-271f-009f-cf7247f3b6c2@amsat.org> <916b95b2-c128-69e0-6e68-78daa0b15722@amsat.org> <20210420205933.GF4440@xz-x1> In-Reply-To: <20210420205933.GF4440@xz-x1> From: Peter Maydell Date: Wed, 21 Apr 2021 12:05:08 +0100 Message-ID: Subject: Re: [PATCH v3] memory: Directly dispatch alias accesses on origin memory region To: Peter Xu Content-Type: text/plain; charset="UTF-8" Received-SPF: pass client-ip=2a00:1450:4864:20::629; envelope-from=peter.maydell@linaro.org; helo=mail-ej1-x629.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Michael S. Tsirkin" , Alexey Kardashevskiy , Richard Henderson , Mark Cave-Ayland , =?UTF-8?Q?Philippe_Mathieu=2DDaud=C3=A9?= , QEMU Developers , Jan Kiszka , Paolo Bonzini , Igor Mammedov , David Gibson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 20 Apr 2021 at 21:59, Peter Xu wrote: > I think it should always be a valid request to trigger memory access via the MR > layer, say, what if the caller has no address space context at all? From the > name of memory_region_dispatch_write|read I don't see either on why we should > not take care of alias mrs. That's also the reason I'd even prefer this patch > rather than an assert. It's a bit of an odd case to need to do direct accesses on an MR (so if you think you need to you should probably look for whether there's a better way to do it), but there are sometimes reasons it's necessary or expedient -- we have about half a dozen uses which aren't part of the core memory system using memory_region_dispatch_* as an internal function. So I think I agree that while we have this as an API exposed to the rest of the system it would be nice if it Just Worked for alias MRs. thanks -- PMM