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=-8.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 076A3C433DB for ; Tue, 16 Feb 2021 19:09:17 +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 304D964E28 for ; Tue, 16 Feb 2021 19:09:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 304D964E28 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]:34376 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lC5il-0001aW-6o for qemu-devel@archiver.kernel.org; Tue, 16 Feb 2021 14:09:15 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:44042) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lC5eO-0007GB-O4 for qemu-devel@nongnu.org; Tue, 16 Feb 2021 14:04:44 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:56350) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lC5eM-0003ZS-Vj for qemu-devel@nongnu.org; Tue, 16 Feb 2021 14:04:44 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613502282; 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=DuvFAoAylhF4Tc18kr383p1qsXoAvXnqyEAghDK+Z+s=; b=iL0FvlmO9ne8IUQwM/wEKzUxM9JMXwhpYrHUZuqAU8L45GiI2Sechd7/pGWtqFqUfxHkoC RXcHRK8sXT2hbR22IHqM1ggtIezMXUdp0YPWylcI85B/9GjRhUEyR8qn8pVVRhLpFzN/1X DFBepjYvcTxqG6EVS8jXbDqBIrGqoyw= 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-529-tIicrd-2PAqQMrCVs9vmaQ-1; Tue, 16 Feb 2021 14:04:38 -0500 X-MC-Unique: tIicrd-2PAqQMrCVs9vmaQ-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2812F107ACED; Tue, 16 Feb 2021 19:04:37 +0000 (UTC) Received: from omen.home.shazbot.org (ovpn-112-255.phx2.redhat.com [10.3.112.255]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4589D60C15; Tue, 16 Feb 2021 19:04:24 +0000 (UTC) Date: Tue, 16 Feb 2021 12:04:23 -0700 From: Alex Williamson To: David Hildenbrand Subject: Re: [PATCH v5 00/11] virtio-mem: vfio support Message-ID: <20210216120423.0483b3fc@omen.home.shazbot.org> In-Reply-To: <83763c2d-c0dd-12d8-193d-a58517340015@redhat.com> References: <20210121110540.33704-1-david@redhat.com> <20210127074407-mutt-send-email-mst@kernel.org> <0c34a461-bdfe-3512-b9f6-69bdb2b34f19@redhat.com> <20210216113359.70af1ad4@omen.home.shazbot.org> <83763c2d-c0dd-12d8-193d-a58517340015@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=alex.williamson@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=alex.williamson@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, 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: Pankaj Gupta , Wei Yang , "Michael S. Tsirkin" , Pankaj Gupta , "Dr. David Alan Gilbert" , Peter Xu , qemu-devel@nongnu.org, Auger Eric , Igor Mammedov , teawater , Jonathan Cameron , Paolo Bonzini , Marek Kedzierski Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 16 Feb 2021 19:49:09 +0100 David Hildenbrand wrote: > On 16.02.21 19:33, Alex Williamson wrote: > > On Mon, 15 Feb 2021 15:03:43 +0100 > > David Hildenbrand wrote: > > > >> On 08.02.21 09:28, David Hildenbrand wrote: > >>> On 27.01.21 13:45, Michael S. Tsirkin wrote: > >>>> On Thu, Jan 21, 2021 at 12:05:29PM +0100, David Hildenbrand wrote: > >>>>> A virtio-mem device manages a memory region in guest physical address > >>>>> space, represented as a single (currently large) memory region in QEMU, > >>>>> mapped into system memory address space. Before the guest is allowed to use > >>>>> memory blocks, it must coordinate with the hypervisor (plug blocks). After > >>>>> a reboot, all memory is usually unplugged - when the guest comes up, it > >>>>> detects the virtio-mem device and selects memory blocks to plug (based on > >>>>> resize requests from the hypervisor). > >>>>> > >>>>> Memory hot(un)plug consists of (un)plugging memory blocks via a virtio-mem > >>>>> device (triggered by the guest). When unplugging blocks, we discard the > >>>>> memory - similar to memory balloon inflation. In contrast to memory > >>>>> ballooning, we always know which memory blocks a guest may actually use - > >>>>> especially during a reboot, after a crash, or after kexec (and during > >>>>> hibernation as well). Guests agreed to not access unplugged memory again, > >>>>> especially not via DMA. > >>>>> > >>>>> The issue with vfio is, that it cannot deal with random discards - for this > >>>>> reason, virtio-mem and vfio can currently only run mutually exclusive. > >>>>> Especially, vfio would currently map the whole memory region (with possible > >>>>> only little/no plugged blocks), resulting in all pages getting pinned and > >>>>> therefore resulting in a higher memory consumption than expected (turning > >>>>> virtio-mem basically useless in these environments). > >>>>> > >>>>> To make vfio work nicely with virtio-mem, we have to map only the plugged > >>>>> blocks, and map/unmap properly when plugging/unplugging blocks (including > >>>>> discarding of RAM when unplugging). We achieve that by using a new notifier > >>>>> mechanism that communicates changes. > >>>> > >>>> series > >>>> > >>>> Acked-by: Michael S. Tsirkin > >>>> > >>>> virtio bits > >>>> > >>>> Reviewed-by: Michael S. Tsirkin > >>>> > >>>> This needs to go through vfio tree I assume. > >>> > >>> Thanks Michael. > >>> > >>> @Alex, what are your suggestions? > >> > >> Gentle ping. > > > > Sorry for the delay. It looks to me like patches 1, 8, and 9 are > > Memory API that are still missing an Ack from Paolo. I'll toss in my > > A-b+R-b for patches 6 and 7. I don't see that this necessarily needs > > to go in through vfio, I'm more than happy if someone else wants to > > grab it. Thanks, > > Thanks, I assume patch #11 is fine with you as well? Yep, sent my acks for it as well. Thanks, Alex > @Paolo, it would be great if I can get your feedback on patch #1. I have > more stuff coming up that will reuse RamDiscardMgr (i.e., for better > migration handling and better guest memory dump handling). >