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=-6.6 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 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 16669C4BA0F for ; Wed, 26 Feb 2020 08:13:43 +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 DA9502084E for ; Wed, 26 Feb 2020 08:13:42 +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="Zt4aQoQN" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DA9502084E 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]:39678 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j6rp8-0007jD-2E for qemu-devel@archiver.kernel.org; Wed, 26 Feb 2020 03:13:42 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:40865) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j6roY-0007GT-6e for qemu-devel@nongnu.org; Wed, 26 Feb 2020 03:13:07 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1j6roV-0005wX-SJ for qemu-devel@nongnu.org; Wed, 26 Feb 2020 03:13:04 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:37788 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1j6roV-0005s0-Io for qemu-devel@nongnu.org; Wed, 26 Feb 2020 03:13:03 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1582704782; 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=eq/lNXDfH0npSs6YBZgMhPnYI1gm2uORmmjtAflxvBY=; b=Zt4aQoQNLqBND5wVeCTS8EugJc7LsOyZfZa31eDKogezwxMZN0fZvh4YL0IfThy9jEJw/3 EUOasmGlET3dSRcuJ6uWciMey6TIXrTZIO4AHbzMFSqiYgA47cZEJRQWhBDUhuvcVOGCC6 g0B/6P/sLiwAH4aOAvAur3lbqHg/oX8= 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-163-zaEB1lWHPrmE_DUst110KQ-1; Wed, 26 Feb 2020 03:12:58 -0500 X-MC-Unique: zaEB1lWHPrmE_DUst110KQ-1 Received: by mail-qk1-f198.google.com with SMTP id i11so3045376qki.12 for ; Wed, 26 Feb 2020 00:12:58 -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:in-reply-to; bh=MtgsRwg8tm0JrYCU5RQEw+IggaDLVkEE11eBrk9zP8A=; b=g2VfG1Yl7y5ApHTFPE/DB2zrHhtrivqgGYw0u4KQ99MtUuxRqGb+BU6veRnle0JEwC iaQALeQSTrAQrUlAP6erVpskZbuYu+iy5e9h5gWkKqBQxQZErxJEngBQOeM+2jEA7rpy r4GDhrcRwwfZHMZ8iCo4kYRFAVBfAn2PwMTGrH+Gi11MVjemMvvNWrpYGgZjUwTbFlWJ qRuBM9831sbomeUIy5Lirq/+skmj6LxFfTXdD1bSmNLvN2uClRaLRZ2RHTklS+pv+Giu y80FIvkFBd2d5xWxLJ1vKGwENisgSf/58srV3N4PRMH1qPTxxA7kdrIFt/+hixDT6Ruk HLVA== X-Gm-Message-State: APjAAAWpjJP2fXj4Y+qMAplRo4bPO0dygCfuxlK/os2WJozaqG92viXc kcReJtp/rJHfCcpkbQzgWGAZutDymN+c50ZYwC+ELGGf6GpdY4eaKJZuaPd+SrAQdpUI5//emxq hovU3W6tt/6A0v48= X-Received: by 2002:ac8:67d7:: with SMTP id r23mr3880971qtp.20.1582704778193; Wed, 26 Feb 2020 00:12:58 -0800 (PST) X-Google-Smtp-Source: APXvYqzLJaeyasLFT2boYI9DCJg1NbFMj6foUmUfdgrXf5NdRnYTog5JCW77aSXcMyOdMKv3cmtHXw== X-Received: by 2002:ac8:67d7:: with SMTP id r23mr3880953qtp.20.1582704777926; Wed, 26 Feb 2020 00:12:57 -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 z5sm741440qta.7.2020.02.26.00.12.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Feb 2020 00:12:57 -0800 (PST) Date: Wed, 26 Feb 2020 03:12:52 -0500 From: "Michael S. Tsirkin" To: Jason Wang Subject: Re: [PATCH] vhost: correctly turn on VIRTIO_F_IOMMU_PLATFORM Message-ID: <20200226030945-mutt-send-email-mst@kernel.org> References: <20200226070647.8103-1-jasowang@redhat.com> <20200226020836-mutt-send-email-mst@kernel.org> <344493874.10686339.1582701636434.JavaMail.zimbra@redhat.com> MIME-Version: 1.0 In-Reply-To: <344493874.10686339.1582701636434.JavaMail.zimbra@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 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: pasic@linux.ibm.com, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Feb 26, 2020 at 02:20:36AM -0500, Jason Wang wrote: >=20 >=20 > ----- Original Message ----- > > On Wed, Feb 26, 2020 at 03:06:47PM +0800, Jason Wang wrote: > > > We turn on device IOTLB via VIRTIO_F_IOMMU_PLATFORM unconditionally o= n > > > platform without IOMMU support. This can lead unnecessary IOTLB > > > transactions which will damage the performance. > > >=20 > > > Fixing this by check whether the device is backed by IOMMU and disabl= e > > > device IOTLB. > > >=20 > > > Reported-by: Halil Pasic > > > Fixes: c471ad0e9bd46 ("vhost_net: device IOTLB support") > > > Signed-off-by: Jason Wang > > > --- > > > hw/virtio/vhost.c | 12 +++++++++++- > > > 1 file changed, 11 insertions(+), 1 deletion(-) > > >=20 > > > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c > > > index 9edfadc81d..6e12c3d2de 100644 > > > --- a/hw/virtio/vhost.c > > > +++ b/hw/virtio/vhost.c > > > @@ -290,7 +290,14 @@ static int vhost_dev_has_iommu(struct vhost_dev = *dev) > > > { > > > VirtIODevice *vdev =3D dev->vdev; > > > =20 > > > - return virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM); > > > + /* > > > + * For vhost, VIRTIO_F_IOMMU_PLATFORM means the backend support > > > + * incremental memory mapping API via IOTLB API. For platform th= at > > > + * does not have IOMMU, there's no need to enable this feature > > > + * which may cause unnecessary IOTLB miss/update trnasactions. > > > + */ > > > + return vdev->dma_as !=3D &address_space_memory && > > > + virtio_has_feature(dev->acked_features, > > > VIRTIO_F_IOMMU_PLATFORM); > > > } > > > =20 > > > static void *vhost_memory_map(struct vhost_dev *dev, hwaddr addr, > >=20 > > Why check acked_features and not host features here? > > I'd worry that if we do it like this, userspace driver > > within guest can clear the feature and make device access > > memory directly. >=20 > Right, host_features should be more than enough. >=20 > >=20 > > > @@ -765,6 +772,9 @@ static int vhost_dev_set_features(struct vhost_de= v > > > *dev, > > > if (enable_log) { > > > features |=3D 0x1ULL << VHOST_F_LOG_ALL; > > > } > > > + if (dev->vdev->dma_as =3D=3D &address_space_memory) { > > > + features &=3D ~(0x1ULL << VIRTIO_F_IOMMU_PLATFORM); > > > + } > >=20 > >=20 > > That's a guest visible change. Which seems at best unnecessary. > > >=20 > I don't get how this can be visible from guest? It works as F_LOG_ALL. >=20 > Thanks Oh you are right. So just call vhost_dev_has_iommu here too? > > > r =3D dev->vhost_ops->vhost_set_features(dev, features); > > > if (r < 0) { > > > VHOST_OPS_DEBUG("vhost_set_features failed"); > > > -- > > > 2.19.1 > >=20 > >=20