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=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 1CE95C433DB for ; Mon, 22 Feb 2021 18:07:02 +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 A04D064E15 for ; Mon, 22 Feb 2021 18:07:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A04D064E15 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]:44658 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lEFbo-00034D-N4 for qemu-devel@archiver.kernel.org; Mon, 22 Feb 2021 13:07:00 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:53726) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lEFK4-0001Ws-QM for qemu-devel@nongnu.org; Mon, 22 Feb 2021 12:48:40 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:27790) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lEFK1-00022W-Qr for qemu-devel@nongnu.org; Mon, 22 Feb 2021 12:48:40 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1614016116; 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=nP1PZoxlNW+qMpGXzOj0SGa8MkHEpQBJTCSxH09F34g=; b=QbMihySCf5hJeO/bOS7M2I1NnJIgHFygX28JGYk4j9BaWbp0LjcytVvo/ic6xwMrEu/bLs uqwFa+4KxsclE0ovthIBCYzI5lv19mDCd8hfwLkz++ePSs7z1/WbBLVBAJeqZkb2ZPQpTr avktSYE8dXuFT9OiFsW/xhrAFzwLGWI= 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-476-lor-cN4AP-q8vwG5HZhPYw-1; Mon, 22 Feb 2021 12:48:30 -0500 X-MC-Unique: lor-cN4AP-q8vwG5HZhPYw-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 8BC6C107ACC7; Mon, 22 Feb 2021 17:48:29 +0000 (UTC) Received: from [10.36.115.16] (ovpn-115-16.ams2.redhat.com [10.36.115.16]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1AF045C255; Mon, 22 Feb 2021 17:48:06 +0000 (UTC) To: Paolo Bonzini , qemu-devel@nongnu.org References: <20210222115708.7623-1-david@redhat.com> <20210222115708.7623-2-david@redhat.com> <7137d1ad-2741-7536-5a3c-58d0c4f8306b@redhat.com> <0277759d-bb9a-6bf3-0ca4-53d3f7ec98f5@redhat.com> <24562156-457f-90b5-dcaf-c55fba1e881b@redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Subject: Re: [PATCH v6 01/12] memory: Introduce RamDiscardMgr for RAM memory regions Message-ID: Date: Mon, 22 Feb 2021 18:48:06 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: 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=63.128.21.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H4=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: Pankaj Gupta , Wei Yang , "Michael S . Tsirkin" , Alex Williamson , Peter Xu , "Dr . David Alan Gilbert" , Auger Eric , Pankaj Gupta , teawater , Igor Mammedov , Marek Kedzierski Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 22.02.21 18:37, Paolo Bonzini wrote: > On 22/02/21 15:53, David Hildenbrand wrote: >>> Yes, but does it behave more like the IOMMU notifier in other regards? >>> :)  The IOMMU notifier is concerned with an iova concept that doesn't >>> exist at the MemoryRegion level, while RamDiscardListener works at the >>> (MemoryRegion, offset) level that can easily be represented by a >>> MemoryRegionSection.  Using MemoryRegionSection might even simplify the >>> listener code. >> >> It's similarly concerned with rather small, lightweight updates I would >> say. > > Why does that matter? I think if it's concerned with the MemoryRegion > address space it should use MemoryListener and MemoryRegionSection. > >>>> The main motivation is to let listener decide how it wants to handle the >>>> memory region. For example, for vhost, vdpa, kvm, ... I only want a >>>> single region, not separate ones for each and every populated range, >>>> punching out discarded ranges. Note that there are cases (i.e., >>>> anonymous memory), where it's even valid for the guest to read discarded >>>> memory. >>> >>> Yes, I agree with that.  You would still have the same >>> region-add/region_nop/region_del callbacks for KVM and friends; on top >>> of that you would have region_populate/region_discard callbacks for VFIO. >> >> I think instead of region_populate/region_discard we would want >> individual region_add/region_del when populating/discarding for all >> MemoryListeners that opt-in somehow (e.g., VFIO, dump-guest-memory, >> ...). Similarly, we would want to call log_sync()/log_clear() then only >> for these parts. >> >> But what happens when I populate/discard some memory? I don't want to >> trigger an address space transaction (begin()...region_nop()...commit()) >> - whenever I populate/discard memory (e.g., in 2 MB granularity). >> Especially not, if nothing might have changed for most other >> MemoryListeners. > > Right, that was the reason why I was suggesting different callbacks. > For the VFIO listener, which doesn't have begin or commit callbacks, I > think you could just rename region_add to region_populate, and point > both region_del and region_discard to the existing region_del commit. > > Calling log_sync/log_clear only for populated parts also makes sense. > log_sync and log_clear do not have to be within begin/commit, so you can > change the semantics to call them more than once. I'll prototype to see how it looks/feels. As long as it's moving logic out of the VFIO code into the address space update code it could be quite alright. -- Thanks, David / dhildenb