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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, 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 E53CFC433E0 for ; Tue, 16 Feb 2021 18:36:18 +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 7945364E2B for ; Tue, 16 Feb 2021 18:36:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7945364E2B 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]:38480 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lC5Cq-0002Rh-I8 for qemu-devel@archiver.kernel.org; Tue, 16 Feb 2021 13:36:16 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:36292) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lC5BH-00010L-S3 for qemu-devel@nongnu.org; Tue, 16 Feb 2021 13:34:39 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:42771) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lC5BF-0008JM-VY for qemu-devel@nongnu.org; Tue, 16 Feb 2021 13:34:39 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613500477; 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=b9nF/1Mw1v1reYLVc00NSBWoTWPZv6cviZTpFQZ7xX4=; b=GsY4B9kAyL8QVwpdcWUzH1+roHs2cDJbNO0sIYrpsHpQjTzoR3PDx3cQum4CqzyqhmfYsb BGAM/mHMrfFK1pbZK1w0rDvw56EXVSbXThgiJinU9D1NYwL98C+vYByH2lz4rhEbbTjmZp BSih76XtJa9fUypHYDoj4LNnFl0cbTE= 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-571-d5anyg-XOHKRP5XW4fSszA-1; Tue, 16 Feb 2021 13:34:33 -0500 X-MC-Unique: d5anyg-XOHKRP5XW4fSszA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8345010082F8; Tue, 16 Feb 2021 18:34:32 +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 AEFB670481; Tue, 16 Feb 2021 18:34:31 +0000 (UTC) Date: Tue, 16 Feb 2021 11:34:14 -0700 From: Alex Williamson To: David Hildenbrand Subject: Re: [PATCH v5 07/11] vfio: Support for RamDiscardMgr in the vIOMMU case Message-ID: <20210216113414.6cfd089c@omen.home.shazbot.org> In-Reply-To: <20210121110540.33704-8-david@redhat.com> References: <20210121110540.33704-1-david@redhat.com> <20210121110540.33704-8-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 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" , Jonathan Cameron , qemu-devel@nongnu.org, Peter Xu , "Dr . David Alan Gilbert" , Auger Eric , teawater , Igor Mammedov , Paolo Bonzini , Marek Kedzierski Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, 21 Jan 2021 12:05:36 +0100 David Hildenbrand wrote: > vIOMMU support works already with RamDiscardMgr as long as guests only > map populated memory. Both, populated and discarded memory is mapped > into &address_space_memory, where vfio_get_xlat_addr() will find that > memory, to create the vfio mapping. > > Sane guests will never map discarded memory (e.g., unplugged memory > blocks in virtio-mem) into an IOMMU - or keep it mapped into an IOMMU while > memory is getting discarded. However, there are two cases where a malicious > guests could trigger pinning of more memory than intended. > > One case is easy to handle: the guest trying to map discarded memory > into an IOMMU. > > The other case is harder to handle: the guest keeping memory mapped in > the IOMMU while it is getting discarded. We would have to walk over all > mappings when discarding memory and identify if any mapping would be a > violation. Let's keep it simple for now and print a warning, indicating > that setting RLIMIT_MEMLOCK can mitigate such attacks. > > We have to take care of incoming migration: at the point the > IOMMUs get restored and start creating mappings in vfio, RamDiscardMgr > implementations might not be back up and running yet: let's add runstate > priorities to enforce the order when restoring. > > 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 > --- > hw/vfio/common.c | 35 +++++++++++++++++++++++++++++++++++ Acked-by: Alex Williamson Reviewed-by: Alex Williamson > hw/virtio/virtio-mem.c | 1 + > include/migration/vmstate.h | 1 + > 3 files changed, 37 insertions(+) > > diff --git a/hw/vfio/common.c b/hw/vfio/common.c > index 166ec6ec62..15ecd05a4b 100644 > --- a/hw/vfio/common.c > +++ b/hw/vfio/common.c > @@ -36,6 +36,7 @@ > #include "qemu/range.h" > #include "sysemu/kvm.h" > #include "sysemu/reset.h" > +#include "sysemu/runstate.h" > #include "trace.h" > #include "qapi/error.h" > #include "migration/migration.h" > @@ -574,6 +575,40 @@ static bool vfio_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr, > error_report("iommu map to non memory area %"HWADDR_PRIx"", > xlat); > return false; > + } else if (memory_region_has_ram_discard_mgr(mr)) { > + RamDiscardMgr *rdm = memory_region_get_ram_discard_mgr(mr); > + RamDiscardMgrClass *rdmc = RAM_DISCARD_MGR_GET_CLASS(rdm); > + > + /* > + * Malicious VMs can map memory into the IOMMU, which is expected > + * to remain discarded. vfio will pin all pages, populating memory. > + * Disallow that. vmstate priorities make sure any RamDiscardMgr were > + * already restored before IOMMUs are restored. > + */ > + if (!rdmc->is_populated(rdm, mr, xlat, len)) { > + error_report("iommu map to discarded memory (e.g., unplugged via" > + " virtio-mem): %"HWADDR_PRIx"", > + iotlb->translated_addr); > + return false; > + } > + > + /* > + * Malicious VMs might trigger discarding of IOMMU-mapped memory. The > + * pages will remain pinned inside vfio until unmapped, resulting in a > + * higher memory consumption than expected. If memory would get > + * populated again later, there would be an inconsistency between pages > + * pinned by vfio and pages seen by QEMU. This is the case until > + * unmapped from the IOMMU (e.g., during device reset). > + * > + * With malicious guests, we really only care about pinning more memory > + * than expected. RLIMIT_MEMLOCK set for the user/process can never be > + * exceeded and can be used to mitigate this problem. > + */ > + warn_report_once("Using vfio with vIOMMUs and coordinated discarding of" > + " RAM (e.g., virtio-mem) works, however, malicious" > + " guests can trigger pinning of more memory than" > + " intended via an IOMMU. It's possible to mitigate " > + " by setting/adjusting RLIMIT_MEMLOCK."); > } > > /* > diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c > index 6200813bb8..f419a758f3 100644 > --- a/hw/virtio/virtio-mem.c > +++ b/hw/virtio/virtio-mem.c > @@ -871,6 +871,7 @@ static const VMStateDescription vmstate_virtio_mem_device = { > .name = "virtio-mem-device", > .minimum_version_id = 1, > .version_id = 1, > + .priority = MIG_PRI_VIRTIO_MEM, > .post_load = virtio_mem_post_load, > .fields = (VMStateField[]) { > VMSTATE_WITH_TMP(VirtIOMEM, VirtIOMEMMigSanityChecks, > diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h > index 075ee80096..3bf58ff043 100644 > --- a/include/migration/vmstate.h > +++ b/include/migration/vmstate.h > @@ -153,6 +153,7 @@ typedef enum { > MIG_PRI_DEFAULT = 0, > MIG_PRI_IOMMU, /* Must happen before PCI devices */ > MIG_PRI_PCI_BUS, /* Must happen before IOMMU */ > + MIG_PRI_VIRTIO_MEM, /* Must happen before IOMMU */ > MIG_PRI_GICV3_ITS, /* Must happen before PCI devices */ > MIG_PRI_GICV3, /* Must happen before the ITS */ > MIG_PRI_MAX,