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=-15.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 4C52CC433E0 for ; Wed, 10 Mar 2021 08:43:48 +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 A967764FE7 for ; Wed, 10 Mar 2021 08:43:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A967764FE7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:37888 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lJuRW-0003bV-QO for qemu-devel@archiver.kernel.org; Wed, 10 Mar 2021 03:43:46 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:40952) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lJuPt-0002XM-7b for qemu-devel@nongnu.org; Wed, 10 Mar 2021 03:42:05 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:58040) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lJuPr-0003uo-45 for qemu-devel@nongnu.org; Wed, 10 Mar 2021 03:42:04 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1615365722; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=joYhIbpcPaNp3ElSvifk+utKlJY+NCRnEW8oQTSJon8=; b=iTWonuP1jPfxISXh0MZp1y6Z/L+0WhSt5Wl93tJHOCs0/0XUCYZXtoDLVih3jQXr8Sc4i8 AodAgQIV5YX37Iq0m79MwMoPRjwN8xRqgChH8pFtnlJM0oZSMRY4J3hYWh/1QZc2ZZ0Vc3 3CMlxURSHIZcnhrgOzF40XTmoT+rKJY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-169-KqTSe9R1NrC6QqbJ_wd5Zw-1; Wed, 10 Mar 2021 03:42:00 -0500 X-MC-Unique: KqTSe9R1NrC6QqbJ_wd5Zw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5A01F8018A7; Wed, 10 Mar 2021 08:41:58 +0000 (UTC) Received: from [10.36.114.87] (ovpn-114-87.ams2.redhat.com [10.36.114.87]) by smtp.corp.redhat.com (Postfix) with ESMTP id BA0DE5C261; Wed, 10 Mar 2021 08:41:43 +0000 (UTC) To: Peter Xu References: <20210309200451.GF763132@xz-x1> <29372C8B-7F57-4AB6-99DB-5E73179D7555@redhat.com> <20210309205809.GI763132@xz-x1> From: David Hildenbrand Organization: Red Hat GmbH Subject: Re: [PATCH v3 09/12] util/mmap-alloc: Pass flags instead of separate bools to qemu_ram_mmap() Message-ID: <8f1f955d-f3b8-298b-eb43-b5d51824af44@redhat.com> Date: Wed, 10 Mar 2021 09:41:42 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: <20210309205809.GI763132@xz-x1> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.251, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, 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: Marcel Apfelbaum , Cornelia Huck , Eduardo Habkost , "Michael S. Tsirkin" , Stefan Weil , Murilo Opsfelder Araujo , Richard Henderson , "Dr. David Alan Gilbert" , Juan Quintela , qemu-devel@nongnu.org, Halil Pasic , Christian Borntraeger , Greg Kurz , Stefan Hajnoczi , Igor Mammedov , Thomas Huth , Paolo Bonzini , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , Igor Kotrasinski Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 09.03.21 21:58, Peter Xu wrote: > On Tue, Mar 09, 2021 at 09:27:10PM +0100, David Hildenbrand wrote: >> >>> Am 09.03.2021 um 21:04 schrieb Peter Xu : >>> >>> On Mon, Mar 08, 2021 at 04:05:57PM +0100, David Hildenbrand wrote: >>>> Let's introduce a new set of flags that abstract mmap logic and replace >>>> our current set of bools, to prepare for another flag. >>>> >>>> Signed-off-by: David Hildenbrand >>>> --- >>>> include/qemu/mmap-alloc.h | 17 +++++++++++------ >>>> softmmu/physmem.c | 8 +++++--- >>>> util/mmap-alloc.c | 14 +++++++------- >>>> util/oslib-posix.c | 3 ++- >>>> 4 files changed, 25 insertions(+), 17 deletions(-) >>>> >>>> diff --git a/include/qemu/mmap-alloc.h b/include/qemu/mmap-alloc.h >>>> index 456ff87df1..55664ea9f3 100644 >>>> --- a/include/qemu/mmap-alloc.h >>>> +++ b/include/qemu/mmap-alloc.h >>>> @@ -6,6 +6,15 @@ size_t qemu_fd_getpagesize(int fd); >>>> >>>> size_t qemu_mempath_getpagesize(const char *mem_path); >>>> >>>> +/* Map PROT_READ instead of PROT_READ|PROT_WRITE. */ >>>> +#define QEMU_RAM_MMAP_READONLY (1 << 0) >>>> + >>>> +/* Map MAP_SHARED instead of MAP_PRIVATE. */ >>>> +#define QEMU_RAM_MMAP_SHARED (1 << 1) >>>> + >>>> +/* Map MAP_SYNC|MAP_SHARED_VALIDATE if possible, fallback and warn otherwise. */ >>>> +#define QEMU_RAM_MMAP_PMEM (1 << 2) >>> >>> Sorry to speak late - I just noticed that is_pmem can actually be converted too >>> with "MAP_SYNC | MAP_SHARED_VALIDATE". We can even define MAP_PMEM_EXTRA for >>> use within qemu if we want. Then we can avoid one layer of QEMU_RAM_* by >>> directly using MAP_*, I think? >>> >> >> No problem :) I don‘t think passing in random MAP_ flags is a good interface (we would at least need an allow list). >> >> I like the abstraction / explicit semenatics of QEMU_RAM_MMAP_PMEM as spelled out in the comment. Doing the fallback when passing in the mmap flags is a little ugly. We could do the fallback in the caller, I think I remember there is only a single call site. >> >> PROT_READ won‘t be covered as well, not sure if passing in protections improves the interface. >> >> Long story short, I like the abstraction provided by these flags, only exporting what we actually support/abstracting it, and setting some MAP_ flags automatically (MAP_PRIVATE, MAP_ANON) instead of having to spell that put in the caller. > > Yeh the READONLY flag would be special, it will need to be separated from the > rest flags. I'd keep my own preference, but if you really like the current > way, maybe at least move it to qemu/osdep.h? So at least when someone needs a > cross-platform flag they'll show up - while mmap-alloc.h looks still only for > the posix world, then it'll be odd to introduce these flags only for posix even > if posix definied most of them. I'll give it another thought today. I certainly want to avoid moving all that MAP_ flag and PROT_ logic to the callers. E.g., MAP_SHARED implies !MAP_PRIVATE. MAP_SYNC implies that we want MAP_SHARED_VALIDATE. fd < 0 implies MAP_ANONYMOUS. Maybe something like /* * QEMU's MMAP abstraction to map guest RAM, taking care of alignment * requirements and guard pages. * * Supported flags: MAP_SHARED, MAP_SYNC * * Implicitly set flags: * - MAP PRIVATE: When !MAP_SHARED and !MAP_SYNC * - MAP_ANONYMOUS: When fd < 0 * - MAP_SHARED_VALIDATE: When MAP_SYNC * * If mapping with MAP_SYNC|MAP_SHARED_VALIDATE fails, fallback to * !MAP_SYNC|MAP_SHARED and warn. */ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool readonly, uint32_t mmap_flags, off_t map_offset); I also thought about introducing QEMU_MAP_READONLY 0x100000000ul and using "uint64_t mmap_flags" - thoughts? > > At the meantime, maybe rename QEMU_RAM_MMAP_* to QEMU_MMAP_* too? All of them > look applicable to no-RAM-backends too. Hm, I don't think this is a good idea unless we would have something like qemu_mmap() - which I don't think we'll have in the near future. -- Thanks, David / dhildenb