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=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 63FD2C35669 for ; Mon, 24 Feb 2020 04:02:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2F0672086A for ; Mon, 24 Feb 2020 04:02:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fwSMQHR5" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727247AbgBXECV (ORCPT ); Sun, 23 Feb 2020 23:02:21 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:52204 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727202AbgBXECU (ORCPT ); Sun, 23 Feb 2020 23:02:20 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1582516939; 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: in-reply-to:in-reply-to:references:references; bh=jMt7aQ9pDIFoF8MXPWrUB8nziLJeM4YhEWRgKCHSf8Q=; b=fwSMQHR5qAm6l4Q8qCx9b0y+TskObdabEDJ+T571U3OGfO6fUE6DnqlUjk5Y/hPFJXnU6i eI96yMWqwm3EA2F7KUW8QNFY0uPRhVZPrsvtimNWG+9cxLWMheeNEPXynjRBkkgsctqkuw j3TekEp7pT6er/vb/NuJO0oI26XCt2U= 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-230-8HLUA13KPguNUh1BEEJjqA-1; Sun, 23 Feb 2020 23:02:11 -0500 X-MC-Unique: 8HLUA13KPguNUh1BEEJjqA-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 2DDA213E2; Mon, 24 Feb 2020 04:02:09 +0000 (UTC) Received: from [10.72.13.147] (ovpn-13-147.pek2.redhat.com [10.72.13.147]) by smtp.corp.redhat.com (Postfix) with ESMTP id 13BB460BF4; Mon, 24 Feb 2020 04:01:58 +0000 (UTC) Subject: Re: [PATCH 0/2] virtio: decouple protected guest RAM form VIRTIO_F_IOMMU_PLATFORM To: Halil Pasic Cc: "Michael S. Tsirkin" , Marek Szyprowski , Robin Murphy , Christoph Hellwig , linux-s390@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, Christian Borntraeger , Janosch Frank , Viktor Mihajlovski , Cornelia Huck , Ram Pai , Thiago Jung Bauermann , David Gibson , "Lendacky, Thomas" , Michael Mueller References: <20200220160606.53156-1-pasic@linux.ibm.com> <426e6972-0565-c931-e171-da0f58fbf856@redhat.com> <20200221155602.4de41fa7.pasic@linux.ibm.com> From: Jason Wang Message-ID: <0181712c-e533-fcfd-2638-8a0649d713dd@redhat.com> Date: Mon, 24 Feb 2020 12:01:57 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20200221155602.4de41fa7.pasic@linux.ibm.com> Content-Type: multipart/mixed; boundary="------------323EAFF568B452B8B5C3BA24" Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is a multi-part message in MIME format. --------------323EAFF568B452B8B5C3BA24 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 2020/2/21 =E4=B8=8B=E5=8D=8810:56, Halil Pasic wrote: > On Fri, 21 Feb 2020 14:22:26 +0800 > Jason Wang wrote: > >> On 2020/2/21 =E4=B8=8A=E5=8D=8812:06, Halil Pasic wrote: >>> Currently if one intends to run a memory protection enabled VM with >>> virtio devices and linux as the guest OS, one needs to specify the >>> VIRTIO_F_IOMMU_PLATFORM flag for each virtio device to make the guest >>> linux use the DMA API, which in turn handles the memory >>> encryption/protection stuff if the guest decides to turn itself into >>> a protected one. This however makes no sense due to multiple reasons: >>> * The device is not changed by the fact that the guest RAM is >>> protected. The so called IOMMU bypass quirk is not affected. >>> * This usage is not congruent with standardised semantics of >>> VIRTIO_F_IOMMU_PLATFORM. Guest memory protected is an orthogonal reas= on >>> for using DMA API in virtio (orthogonal with respect to what is >>> expressed by VIRTIO_F_IOMMU_PLATFORM). >>> >>> This series aims to decouple 'have to use DMA API because my (guest) = RAM >>> is protected' and 'have to use DMA API because the device told me >>> VIRTIO_F_IOMMU_PLATFORM'. >>> >>> Please find more detailed explanations about the conceptual aspects i= n >>> the individual patches. There is however also a very practical proble= m >>> that is addressed by this series. >>> >>> For vhost-net the feature VIRTIO_F_IOMMU_PLATFORM has the following s= ide >>> effect The vhost code assumes it the addresses on the virtio descript= or >>> ring are not guest physical addresses but iova's, and insists on doin= g a >>> translation of these regardless of what transport is used (e.g. wheth= er >>> we emulate a PCI or a CCW device). (For details see commit 6b1e6cc785= 5b >>> "vhost: new device IOTLB API".) On s390 this results in severe >>> performance degradation (c.a. factor 10). >> >> Do you see a consistent degradation on the performance, or it only >> happen when for during the beginning of the test? >> > AFAIK the degradation is consistent. > >>> BTW with ccw I/O there is >>> (architecturally) no IOMMU, so the whole address translation makes no >>> sense in the context of virtio-ccw. >> >> I suspect we can do optimization in qemu side. >> >> E.g send memtable entry via IOTLB API when vIOMMU is not enabled. >> >> If this makes sense, I can draft patch to see if there's any differenc= e. > Frankly I would prefer to avoid IOVAs on the descriptor ring (and the > then necessary translation) for virtio-ccw altogether. But Michael > voiced his opinion that we should mandate F_IOMMU_PLATFORM for devices > that could be used with guests running in protected mode. I don't share > his opinion, but that's an ongoing discussion. > > Should we end up having to do translation from IOVA in vhost, we are > very interested in that translation being fast and efficient. > > In that sense we would be very happy to test any optimization that aim > into that direction. > > Thank you very much for your input! Using IOTLB API on platform without IOMMU support is not intended.=20 Please try the attached patch to see if it helps. Thanks > > Regards, > Halil > >> Thanks >> >> >>> Halil Pasic (2): >>> mm: move force_dma_unencrypted() to mem_encrypt.h >>> virtio: let virtio use DMA API when guest RAM is protected >>> >>> drivers/virtio/virtio_ring.c | 3 +++ >>> include/linux/dma-direct.h | 9 --------- >>> include/linux/mem_encrypt.h | 10 ++++++++++ >>> 3 files changed, 13 insertions(+), 9 deletions(-) >>> >>> >>> base-commit: ca7e1fd1026c5af6a533b4b5447e1d2f153e28f2 --------------323EAFF568B452B8B5C3BA24 Content-Type: text/x-patch; name="0001-virtio-turn-on-IOMMU_PLATFORM-properly.patch" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="0001-virtio-turn-on-IOMMU_PLATFORM-properly.patch" >From 66fa730460875ac99e81d7db2334cd16bb1d2b27 Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Mon, 24 Feb 2020 12:00:10 +0800 Subject: [PATCH] virtio: turn on IOMMU_PLATFORM properly When transport does not support IOMMU, we should clear IOMMU_PLATFORM even if the device and vhost claims to support that. This help to avoid the performance overhead caused by unnecessary IOTLB miss/update transactions on such platform. Signed-off-by: Jason Wang --- hw/virtio/virtio-bus.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c index d6332d45c3..2741b9fdd2 100644 --- a/hw/virtio/virtio-bus.c +++ b/hw/virtio/virtio-bus.c @@ -47,7 +47,6 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp) VirtioBusState *bus = VIRTIO_BUS(qbus); VirtioBusClass *klass = VIRTIO_BUS_GET_CLASS(bus); VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev); - bool has_iommu = virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM); Error *local_err = NULL; DPRINTF("%s: plug device.\n", qbus->name); @@ -77,10 +76,11 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp) return; } - if (klass->get_dma_as != NULL && has_iommu) { - virtio_add_feature(&vdev->host_features, VIRTIO_F_IOMMU_PLATFORM); + if (false && klass->get_dma_as != NULL && + virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM)) { vdev->dma_as = klass->get_dma_as(qbus->parent); } else { + virtio_clear_feature(&vdev->host_features, VIRTIO_F_IOMMU_PLATFORM); vdev->dma_as = &address_space_memory; } } -- 2.19.1 --------------323EAFF568B452B8B5C3BA24-- 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=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 5C7BFC35641 for ; Mon, 24 Feb 2020 04:02:25 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (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 1607020675 for ; Mon, 24 Feb 2020 04:02:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fwSMQHR5" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1607020675 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id BDDFF863A3; Mon, 24 Feb 2020 04:02:24 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Q4O3ES92n9FK; Mon, 24 Feb 2020 04:02:23 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by whitealder.osuosl.org (Postfix) with ESMTP id E865E861CF; Mon, 24 Feb 2020 04:02:23 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id C28D1C18DA; Mon, 24 Feb 2020 04:02:23 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 0410BC0177 for ; Mon, 24 Feb 2020 04:02:23 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id E0C0B861D2 for ; Mon, 24 Feb 2020 04:02:22 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id yz3Bu6pfapd2 for ; Mon, 24 Feb 2020 04:02:21 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.120]) by whitealder.osuosl.org (Postfix) with ESMTPS id C4B50861CF for ; Mon, 24 Feb 2020 04:02:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1582516939; 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: in-reply-to:in-reply-to:references:references; bh=jMt7aQ9pDIFoF8MXPWrUB8nziLJeM4YhEWRgKCHSf8Q=; b=fwSMQHR5qAm6l4Q8qCx9b0y+TskObdabEDJ+T571U3OGfO6fUE6DnqlUjk5Y/hPFJXnU6i eI96yMWqwm3EA2F7KUW8QNFY0uPRhVZPrsvtimNWG+9cxLWMheeNEPXynjRBkkgsctqkuw j3TekEp7pT6er/vb/NuJO0oI26XCt2U= 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-230-8HLUA13KPguNUh1BEEJjqA-1; Sun, 23 Feb 2020 23:02:11 -0500 X-MC-Unique: 8HLUA13KPguNUh1BEEJjqA-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 2DDA213E2; Mon, 24 Feb 2020 04:02:09 +0000 (UTC) Received: from [10.72.13.147] (ovpn-13-147.pek2.redhat.com [10.72.13.147]) by smtp.corp.redhat.com (Postfix) with ESMTP id 13BB460BF4; Mon, 24 Feb 2020 04:01:58 +0000 (UTC) Subject: Re: [PATCH 0/2] virtio: decouple protected guest RAM form VIRTIO_F_IOMMU_PLATFORM To: Halil Pasic References: <20200220160606.53156-1-pasic@linux.ibm.com> <426e6972-0565-c931-e171-da0f58fbf856@redhat.com> <20200221155602.4de41fa7.pasic@linux.ibm.com> From: Jason Wang Message-ID: <0181712c-e533-fcfd-2638-8a0649d713dd@redhat.com> Date: Mon, 24 Feb 2020 12:01:57 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20200221155602.4de41fa7.pasic@linux.ibm.com> Content-Type: multipart/mixed; boundary="------------323EAFF568B452B8B5C3BA24" Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Cc: linux-s390@vger.kernel.org, Janosch Frank , "Michael S. Tsirkin" , Cornelia Huck , Ram Pai , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Christian Borntraeger , iommu@lists.linux-foundation.org, David Gibson , Michael Mueller , "Lendacky, Thomas" , Viktor Mihajlovski , Robin Murphy , Christoph Hellwig X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" This is a multi-part message in MIME format. --------------323EAFF568B452B8B5C3BA24 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 2020/2/21 =E4=B8=8B=E5=8D=8810:56, Halil Pasic wrote: > On Fri, 21 Feb 2020 14:22:26 +0800 > Jason Wang wrote: > >> On 2020/2/21 =E4=B8=8A=E5=8D=8812:06, Halil Pasic wrote: >>> Currently if one intends to run a memory protection enabled VM with >>> virtio devices and linux as the guest OS, one needs to specify the >>> VIRTIO_F_IOMMU_PLATFORM flag for each virtio device to make the guest >>> linux use the DMA API, which in turn handles the memory >>> encryption/protection stuff if the guest decides to turn itself into >>> a protected one. This however makes no sense due to multiple reasons: >>> * The device is not changed by the fact that the guest RAM is >>> protected. The so called IOMMU bypass quirk is not affected. >>> * This usage is not congruent with standardised semantics of >>> VIRTIO_F_IOMMU_PLATFORM. Guest memory protected is an orthogonal reas= on >>> for using DMA API in virtio (orthogonal with respect to what is >>> expressed by VIRTIO_F_IOMMU_PLATFORM). >>> >>> This series aims to decouple 'have to use DMA API because my (guest) = RAM >>> is protected' and 'have to use DMA API because the device told me >>> VIRTIO_F_IOMMU_PLATFORM'. >>> >>> Please find more detailed explanations about the conceptual aspects i= n >>> the individual patches. There is however also a very practical proble= m >>> that is addressed by this series. >>> >>> For vhost-net the feature VIRTIO_F_IOMMU_PLATFORM has the following s= ide >>> effect The vhost code assumes it the addresses on the virtio descript= or >>> ring are not guest physical addresses but iova's, and insists on doin= g a >>> translation of these regardless of what transport is used (e.g. wheth= er >>> we emulate a PCI or a CCW device). (For details see commit 6b1e6cc785= 5b >>> "vhost: new device IOTLB API".) On s390 this results in severe >>> performance degradation (c.a. factor 10). >> >> Do you see a consistent degradation on the performance, or it only >> happen when for during the beginning of the test? >> > AFAIK the degradation is consistent. > >>> BTW with ccw I/O there is >>> (architecturally) no IOMMU, so the whole address translation makes no >>> sense in the context of virtio-ccw. >> >> I suspect we can do optimization in qemu side. >> >> E.g send memtable entry via IOTLB API when vIOMMU is not enabled. >> >> If this makes sense, I can draft patch to see if there's any differenc= e. > Frankly I would prefer to avoid IOVAs on the descriptor ring (and the > then necessary translation) for virtio-ccw altogether. But Michael > voiced his opinion that we should mandate F_IOMMU_PLATFORM for devices > that could be used with guests running in protected mode. I don't share > his opinion, but that's an ongoing discussion. > > Should we end up having to do translation from IOVA in vhost, we are > very interested in that translation being fast and efficient. > > In that sense we would be very happy to test any optimization that aim > into that direction. > > Thank you very much for your input! Using IOTLB API on platform without IOMMU support is not intended.=20 Please try the attached patch to see if it helps. Thanks > > Regards, > Halil > >> Thanks >> >> >>> Halil Pasic (2): >>> mm: move force_dma_unencrypted() to mem_encrypt.h >>> virtio: let virtio use DMA API when guest RAM is protected >>> >>> drivers/virtio/virtio_ring.c | 3 +++ >>> include/linux/dma-direct.h | 9 --------- >>> include/linux/mem_encrypt.h | 10 ++++++++++ >>> 3 files changed, 13 insertions(+), 9 deletions(-) >>> >>> >>> base-commit: ca7e1fd1026c5af6a533b4b5447e1d2f153e28f2 --------------323EAFF568B452B8B5C3BA24 Content-Type: text/x-patch; name="0001-virtio-turn-on-IOMMU_PLATFORM-properly.patch" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="0001-virtio-turn-on-IOMMU_PLATFORM-properly.patch" >From 66fa730460875ac99e81d7db2334cd16bb1d2b27 Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Mon, 24 Feb 2020 12:00:10 +0800 Subject: [PATCH] virtio: turn on IOMMU_PLATFORM properly When transport does not support IOMMU, we should clear IOMMU_PLATFORM even if the device and vhost claims to support that. This help to avoid the performance overhead caused by unnecessary IOTLB miss/update transactions on such platform. Signed-off-by: Jason Wang --- hw/virtio/virtio-bus.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c index d6332d45c3..2741b9fdd2 100644 --- a/hw/virtio/virtio-bus.c +++ b/hw/virtio/virtio-bus.c @@ -47,7 +47,6 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp) VirtioBusState *bus = VIRTIO_BUS(qbus); VirtioBusClass *klass = VIRTIO_BUS_GET_CLASS(bus); VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev); - bool has_iommu = virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM); Error *local_err = NULL; DPRINTF("%s: plug device.\n", qbus->name); @@ -77,10 +76,11 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp) return; } - if (klass->get_dma_as != NULL && has_iommu) { - virtio_add_feature(&vdev->host_features, VIRTIO_F_IOMMU_PLATFORM); + if (false && klass->get_dma_as != NULL && + virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM)) { vdev->dma_as = klass->get_dma_as(qbus->parent); } else { + virtio_clear_feature(&vdev->host_features, VIRTIO_F_IOMMU_PLATFORM); vdev->dma_as = &address_space_memory; } } -- 2.19.1 --------------323EAFF568B452B8B5C3BA24 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu --------------323EAFF568B452B8B5C3BA24-- From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH 0/2] virtio: decouple protected guest RAM form VIRTIO_F_IOMMU_PLATFORM Date: Mon, 24 Feb 2020 12:01:57 +0800 Message-ID: <0181712c-e533-fcfd-2638-8a0649d713dd@redhat.com> References: <20200220160606.53156-1-pasic@linux.ibm.com> <426e6972-0565-c931-e171-da0f58fbf856@redhat.com> <20200221155602.4de41fa7.pasic@linux.ibm.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------323EAFF568B452B8B5C3BA24" Return-path: In-Reply-To: <20200221155602.4de41fa7.pasic-tEXmvtCZX7AybS5Ee8rs3A@public.gmane.org> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Sender: "iommu" To: Halil Pasic Cc: linux-s390-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Janosch Frank , "Michael S. Tsirkin" , Cornelia Huck , Ram Pai , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Christian Borntraeger , iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, David Gibson , Michael Mueller , "Lendacky, Thomas" , Viktor Mihajlovski , Robin Murphy , Christoph Hellwig List-Id: virtualization@lists.linuxfoundation.org This is a multi-part message in MIME format. --------------323EAFF568B452B8B5C3BA24 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 2020/2/21 =E4=B8=8B=E5=8D=8810:56, Halil Pasic wrote: > On Fri, 21 Feb 2020 14:22:26 +0800 > Jason Wang wrote: > >> On 2020/2/21 =E4=B8=8A=E5=8D=8812:06, Halil Pasic wrote: >>> Currently if one intends to run a memory protection enabled VM with >>> virtio devices and linux as the guest OS, one needs to specify the >>> VIRTIO_F_IOMMU_PLATFORM flag for each virtio device to make the guest >>> linux use the DMA API, which in turn handles the memory >>> encryption/protection stuff if the guest decides to turn itself into >>> a protected one. This however makes no sense due to multiple reasons: >>> * The device is not changed by the fact that the guest RAM is >>> protected. The so called IOMMU bypass quirk is not affected. >>> * This usage is not congruent with standardised semantics of >>> VIRTIO_F_IOMMU_PLATFORM. Guest memory protected is an orthogonal reas= on >>> for using DMA API in virtio (orthogonal with respect to what is >>> expressed by VIRTIO_F_IOMMU_PLATFORM). >>> >>> This series aims to decouple 'have to use DMA API because my (guest) = RAM >>> is protected' and 'have to use DMA API because the device told me >>> VIRTIO_F_IOMMU_PLATFORM'. >>> >>> Please find more detailed explanations about the conceptual aspects i= n >>> the individual patches. There is however also a very practical proble= m >>> that is addressed by this series. >>> >>> For vhost-net the feature VIRTIO_F_IOMMU_PLATFORM has the following s= ide >>> effect The vhost code assumes it the addresses on the virtio descript= or >>> ring are not guest physical addresses but iova's, and insists on doin= g a >>> translation of these regardless of what transport is used (e.g. wheth= er >>> we emulate a PCI or a CCW device). (For details see commit 6b1e6cc785= 5b >>> "vhost: new device IOTLB API".) On s390 this results in severe >>> performance degradation (c.a. factor 10). >> >> Do you see a consistent degradation on the performance, or it only >> happen when for during the beginning of the test? >> > AFAIK the degradation is consistent. > >>> BTW with ccw I/O there is >>> (architecturally) no IOMMU, so the whole address translation makes no >>> sense in the context of virtio-ccw. >> >> I suspect we can do optimization in qemu side. >> >> E.g send memtable entry via IOTLB API when vIOMMU is not enabled. >> >> If this makes sense, I can draft patch to see if there's any differenc= e. > Frankly I would prefer to avoid IOVAs on the descriptor ring (and the > then necessary translation) for virtio-ccw altogether. But Michael > voiced his opinion that we should mandate F_IOMMU_PLATFORM for devices > that could be used with guests running in protected mode. I don't share > his opinion, but that's an ongoing discussion. > > Should we end up having to do translation from IOVA in vhost, we are > very interested in that translation being fast and efficient. > > In that sense we would be very happy to test any optimization that aim > into that direction. > > Thank you very much for your input! Using IOTLB API on platform without IOMMU support is not intended.=20 Please try the attached patch to see if it helps. Thanks > > Regards, > Halil > >> Thanks >> >> >>> Halil Pasic (2): >>> mm: move force_dma_unencrypted() to mem_encrypt.h >>> virtio: let virtio use DMA API when guest RAM is protected >>> >>> drivers/virtio/virtio_ring.c | 3 +++ >>> include/linux/dma-direct.h | 9 --------- >>> include/linux/mem_encrypt.h | 10 ++++++++++ >>> 3 files changed, 13 insertions(+), 9 deletions(-) >>> >>> >>> base-commit: ca7e1fd1026c5af6a533b4b5447e1d2f153e28f2 --------------323EAFF568B452B8B5C3BA24 Content-Type: text/x-patch; name="0001-virtio-turn-on-IOMMU_PLATFORM-properly.patch" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="0001-virtio-turn-on-IOMMU_PLATFORM-properly.patch" >From 66fa730460875ac99e81d7db2334cd16bb1d2b27 Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Mon, 24 Feb 2020 12:00:10 +0800 Subject: [PATCH] virtio: turn on IOMMU_PLATFORM properly When transport does not support IOMMU, we should clear IOMMU_PLATFORM even if the device and vhost claims to support that. This help to avoid the performance overhead caused by unnecessary IOTLB miss/update transactions on such platform. Signed-off-by: Jason Wang --- hw/virtio/virtio-bus.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c index d6332d45c3..2741b9fdd2 100644 --- a/hw/virtio/virtio-bus.c +++ b/hw/virtio/virtio-bus.c @@ -47,7 +47,6 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp) VirtioBusState *bus = VIRTIO_BUS(qbus); VirtioBusClass *klass = VIRTIO_BUS_GET_CLASS(bus); VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev); - bool has_iommu = virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM); Error *local_err = NULL; DPRINTF("%s: plug device.\n", qbus->name); @@ -77,10 +76,11 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp) return; } - if (klass->get_dma_as != NULL && has_iommu) { - virtio_add_feature(&vdev->host_features, VIRTIO_F_IOMMU_PLATFORM); + if (false && klass->get_dma_as != NULL && + virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM)) { vdev->dma_as = klass->get_dma_as(qbus->parent); } else { + virtio_clear_feature(&vdev->host_features, VIRTIO_F_IOMMU_PLATFORM); vdev->dma_as = &address_space_memory; } } -- 2.19.1 --------------323EAFF568B452B8B5C3BA24 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline --------------323EAFF568B452B8B5C3BA24--