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=-6.9 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 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 EC82CC35679 for ; Mon, 24 Feb 2020 07:49:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 91A8820675 for ; Mon, 24 Feb 2020 07:49:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="AYKvfRb+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727229AbgBXHtM (ORCPT ); Mon, 24 Feb 2020 02:49:12 -0500 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:23503 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726216AbgBXHtM (ORCPT ); Mon, 24 Feb 2020 02:49:12 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1582530549; 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=UJzRHJfOvqED/QVB11a8FY9iUPPI3dbD0rzXCYDhwc0=; b=AYKvfRb+dvh6s+nQSmNoJs8I1zakq3ANxT7qmg3OQ9x8xSYIGp37vt7XY9Q+s7pasiRO5A 6fXkjTdH8Z3IUDrDZg4G17d4/IaI8cpVoBNJCONynES7jzuoirW6jnEu7TdEnBkZshkVpU oCYA/PT3WSjBF+xgi562N/8xSkPeZIs= Received: from mail-qk1-f198.google.com (mail-qk1-f198.google.com [209.85.222.198]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-4-9Pv8hwS5PN6X02wS73yAVw-1; Mon, 24 Feb 2020 02:49:08 -0500 X-MC-Unique: 9Pv8hwS5PN6X02wS73yAVw-1 Received: by mail-qk1-f198.google.com with SMTP id w126so9668329qkb.23 for ; Sun, 23 Feb 2020 23:49:08 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=UJzRHJfOvqED/QVB11a8FY9iUPPI3dbD0rzXCYDhwc0=; b=EnkKO/ZV2nnsUsKPhbSByKLwuSlFCNYScEdd8aSdoA7ekwl5X41GXSPc4xgwR3FKD0 gYWeAf2w/Kn4B+JIUV6ljRbFz1INdysnwKuSRjA9lH5uL23nngxNRbDb2A+MNFm7dN82 DuCbHCK/+QT2BTPUAJlZH0pxx9Xjxk1HIw1P8VSl3DLsEyPkd30x2ubTxu5U6EqwhyR9 5EtC3mokpu+f233ByenN/ihHB4z48FL50tKCDHhnEdc2b/YCbfAYcTvzoCGVmuQn4fIL H+/NufSlkatWobGT/eZSImgK0EXxzODRjj0d/MA1bdWURAAGOIllLCHT2yHeKhAd45iW TjsA== X-Gm-Message-State: APjAAAWm/h4SiFpJ0JQ5OsUBO2oKVO866lE5BgnlaYqam7HWxIUPnHZ4 pP9scEN1gfSACFPJtDf+txu6Xw4KbsKm/zDBkdOD44Aj4ZJ8d0RW2Txl0dt8/iFUpzbKlLe4KTP Pg9QZoUp19TEpx8nHzLXPx6CR X-Received: by 2002:a05:620a:95c:: with SMTP id w28mr44288181qkw.428.1582530547829; Sun, 23 Feb 2020 23:49:07 -0800 (PST) X-Google-Smtp-Source: APXvYqzzBrfPKkWekVzDtkE3twmNvbfgy+awAYxrqVqXXAqxHi9BwToMW+Zbt9HgNgV5bAhK+LRpaQ== X-Received: by 2002:a05:620a:95c:: with SMTP id w28mr44288158qkw.428.1582530547478; Sun, 23 Feb 2020 23:49:07 -0800 (PST) Received: from redhat.com (bzq-79-178-2-214.red.bezeqint.net. [79.178.2.214]) by smtp.gmail.com with ESMTPSA id r37sm5593220qtj.44.2020.02.23.23.49.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 23 Feb 2020 23:49:06 -0800 (PST) Date: Mon, 24 Feb 2020 02:48:59 -0500 From: "Michael S. Tsirkin" To: Jason Wang Cc: Halil Pasic , 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 Subject: Re: [PATCH 0/2] virtio: decouple protected guest RAM form VIRTIO_F_IOMMU_PLATFORM Message-ID: <20200224024641-mutt-send-email-mst@kernel.org> References: <20200220160606.53156-1-pasic@linux.ibm.com> <426e6972-0565-c931-e171-da0f58fbf856@redhat.com> <20200221155602.4de41fa7.pasic@linux.ibm.com> <0181712c-e533-fcfd-2638-8a0649d713dd@redhat.com> <20200224010607-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 24, 2020 at 02:45:03PM +0800, Jason Wang wrote: > > On 2020/2/24 下午2:06, Michael S. Tsirkin wrote: > > On Mon, Feb 24, 2020 at 12:01:57PM +0800, Jason Wang wrote: > > > On 2020/2/21 下午10:56, Halil Pasic wrote: > > > > On Fri, 21 Feb 2020 14:22:26 +0800 > > > > Jason Wang wrote: > > > > > > > > > On 2020/2/21 上午12:06, 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 reason > > > > > > 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 in > > > > > > the individual patches. There is however also a very practical problem > > > > > > that is addressed by this series. > > > > > > > > > > > > For vhost-net the feature VIRTIO_F_IOMMU_PLATFORM has the following side > > > > > > effect The vhost code assumes it the addresses on the virtio descriptor > > > > > > ring are not guest physical addresses but iova's, and insists on doing a > > > > > > translation of these regardless of what transport is used (e.g. whether > > > > > > we emulate a PCI or a CCW device). (For details see commit 6b1e6cc7855b > > > > > > "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 difference. > > > > 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. 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 > > > >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; > > > } > > > } > > > > This seems to clear it unconditionally. I guess it's just a debugging > > patch, the real one will come later? > > > My bad, here's the correct one. > > Thanks > > > > > > > -- > > > 2.19.1 > > > > >From b8a8b582f46bb86c7a745b272db7b744779e5cc7 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..4be64e193e 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); So it looks like this line is unnecessary, but it's an unrelated cleanup, right? > + if (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); Of course any change like that will have to affect migration compat, etc. Can't we clear the bit when we are sending the features to vhost instead? > vdev->dma_as = &address_space_memory; > } > } > -- > 2.19.1 >