From patchwork Thu Jan 21 11:05:35 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 1429743 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=hLKFguoW; dkim-atps=neutral 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 ozlabs.org (Postfix) with ESMTPS id 4DM09x4XV5z9sTD for ; Thu, 21 Jan 2021 22:13:09 +1100 (AEDT) Received: from localhost ([::1]:47840 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l2Xtj-0005XM-Hf for incoming@patchwork.ozlabs.org; Thu, 21 Jan 2021 06:13:07 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:47252) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l2Xo3-000714-26 for qemu-devel@nongnu.org; Thu, 21 Jan 2021 06:07:15 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:41450) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l2Xo1-0006uN-5P for qemu-devel@nongnu.org; Thu, 21 Jan 2021 06:07:14 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611227232; 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=F1eULhF2tyFRkP1zUYI/GYmvW16zwAnBRia2WSMsPkM=; b=hLKFguoWRAsdn0bLKSGLkQgJAFck2vjofYj/xgClyoRS62I/ktCQyV5IMQxmQqTBeLoGzo kwSK0SR9Sfy4wBAmUduKRIS7wi+/oGn5k8VS+9dH7Ms/PWJMi8al3hBxEMj5e/CjWSWvHw NeW8My0xF1g4+TeQ2DSE8Oi60MlDOus= 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-462-uIkcf6o5PpuFeYNTufFFkw-1; Thu, 21 Jan 2021 06:07:08 -0500 X-MC-Unique: uIkcf6o5PpuFeYNTufFFkw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 733C5100C600; Thu, 21 Jan 2021 11:07:07 +0000 (UTC) Received: from t480s.redhat.com (ovpn-115-70.ams2.redhat.com [10.36.115.70]) by smtp.corp.redhat.com (Postfix) with ESMTP id D340710013BD; Thu, 21 Jan 2021 11:06:55 +0000 (UTC) From: David Hildenbrand To: qemu-devel@nongnu.org Subject: [PATCH v5 06/11] vfio: Sanity check maximum number of DMA mappings with RamDiscardMgr Date: Thu, 21 Jan 2021 12:05:35 +0100 Message-Id: <20210121110540.33704-7-david@redhat.com> In-Reply-To: <20210121110540.33704-1-david@redhat.com> References: <20210121110540.33704-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 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 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: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.167, 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_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 , David Hildenbrand , "Michael S. Tsirkin" , "Dr . David Alan Gilbert" , Peter Xu , Marek Kedzierski , Auger Eric , Alex Williamson , teawater , Jonathan Cameron , Paolo Bonzini , Igor Mammedov Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" Although RamDiscardMgr can handle running into the maximum number of DMA mappings by propagating errors when creating a DMA mapping, we want to sanity check and warn the user early that there is a theoretical setup issue and that virtio-mem might not be able to provide as much memory towards a VM as desired. As suggested by Alex, let's use the number of KVM memory slots to guess how many other mappings we might see over time. Cc: Paolo Bonzini Cc: "Michael S. Tsirkin" Cc: Alex Williamson Cc: Dr. David Alan Gilbert Cc: Igor Mammedov Cc: Pankaj Gupta Cc: Peter Xu Cc: Auger Eric Cc: Wei Yang Cc: teawater Cc: Marek Kedzierski Signed-off-by: David Hildenbrand Acked-by: Alex Williamson --- hw/vfio/common.c | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) diff --git a/hw/vfio/common.c b/hw/vfio/common.c index 78be813a53..166ec6ec62 100644 --- a/hw/vfio/common.c +++ b/hw/vfio/common.c @@ -761,6 +761,49 @@ static void vfio_register_ram_discard_notifier(VFIOContainer *container, vfio_ram_discard_notify_discard_all); rdmc->register_listener(rdm, section->mr, &vrdl->listener); QLIST_INSERT_HEAD(&container->vrdl_list, vrdl, next); + + /* + * Sanity-check if we have a theoretically problematic setup where we could + * exceed the maximum number of possible DMA mappings over time. We assume + * that each mapped section in the same address space as a RamDiscardMgr + * section consumes exactly one DMA mapping, with the exception of + * RamDiscardMgr sections; i.e., we don't expect to have gIOMMU sections in + * the same address space as RamDiscardMgr sections. + * + * We assume that each section in the address space consumes one memslot. + * We take the number of KVM memory slots as a best guess for the maximum + * number of sections in the address space we could have over time, + * also consuming DMA mappings. + */ + if (container->dma_max_mappings) { + unsigned int vrdl_count = 0, vrdl_mappings = 0, max_memslots = 512; + +#ifdef CONFIG_KVM + if (kvm_enabled()) { + max_memslots = kvm_get_max_memslots(); + } +#endif + + QLIST_FOREACH(vrdl, &container->vrdl_list, next) { + hwaddr start, end; + + start = QEMU_ALIGN_DOWN(vrdl->offset_within_address_space, + vrdl->granularity); + end = ROUND_UP(vrdl->offset_within_address_space + vrdl->size, + vrdl->granularity); + vrdl_mappings += (end - start) / vrdl->granularity; + vrdl_count++; + } + + if (vrdl_mappings + max_memslots - vrdl_count > + container->dma_max_mappings) { + warn_report("%s: possibly running out of DMA mappings. E.g., try" + " increasing the 'block-size' of virtio-mem devies." + " Maximum possible DMA mappings: %d, Maximum possible" + " memslots: %d", __func__, container->dma_max_mappings, + max_memslots); + } + } } static void vfio_unregister_ram_discard_listener(VFIOContainer *container,