From nobody Mon Feb 9 08:57:30 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=fail; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1628049062695785.7121308769035; Tue, 3 Aug 2021 20:51:02 -0700 (PDT) Received: from localhost ([::1]:59938 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mB7vp-0003i6-Oq for importer@patchew.org; Tue, 03 Aug 2021 23:51:01 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:44828) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mB7tW-0007Nq-Vs for qemu-devel@nongnu.org; Tue, 03 Aug 2021 23:48:39 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:47772) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mB7tV-0000Xl-Fz for qemu-devel@nongnu.org; Tue, 03 Aug 2021 23:48:38 -0400 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-586-0qIvhXUPO3yqsA-lJhBBDQ-1; Tue, 03 Aug 2021 23:48:33 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 4A1D31006C80; Wed, 4 Aug 2021 03:48:32 +0000 (UTC) Received: from localhost.localdomain (ovpn-12-234.pek2.redhat.com [10.72.12.234]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7CAA560854; Wed, 4 Aug 2021 03:48:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1628048916; 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=B53R/rsTTsnu/S11HHR43iScLS7sGCsbwUGyB2wxgHI=; b=CI8B+SgavcAB6g/zJDvHsFrzTde2MgTtlPGXcLZhfCW0PW8xMHkCme7SZeTSbkmHPHp46b No9mXppU20Vgxxdt2WrXmiimJ/Re4Z+NRJ06c+LG1/QfwplJo2IfzVuG3DUlZP2eUbacie 90Y5jlCoI6k1Pj9xAzslZSZdgKryNAQ= X-MC-Unique: 0qIvhXUPO3yqsA-lJhBBDQ-1 From: Jason Wang To: qemu-devel@nongnu.org Subject: [PATCH 3/3] vhost: correctly detect the enabling IOMMU Date: Wed, 4 Aug 2021 11:48:03 +0800 Message-Id: <20210804034803.1644-4-jasowang@redhat.com> In-Reply-To: <20210804034803.1644-1-jasowang@redhat.com> References: <20210804034803.1644-1-jasowang@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jasowang@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=jasowang@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.699, 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: mst@redhat.com, Jason Wang , Wei.Huang2@amd.com, dgilbert@redhat.com, peterx@redhat.com, Sriyash.Caculo@amd.com, pbonzini@redhat.com, chao.gao@intel.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZM-MESSAGEID: 1628049064598100001 Content-Type: text/plain; charset="utf-8" Vhost used to compare the dma_as against the address_space_memory to detect whether the IOMMU is enabled or not. This might not work well since the virito-bus may call get_dma_as if VIRTIO_F_IOMMU_PLATFORM is set without an actual IOMMU enabled when device is plugged. In the case of PCI where pci_get_address_space() is used, the bus master as is returned. So vhost actually tries to enable device IOTLB even if the IOMMU is not enabled. This will lead a lots of unnecessary transactions between vhost and Qemu and will introduce a huge drop of the performance. For PCI, an ideal approach is to use pci_device_iommu_address_space() just for get_dma_as. But Qemu may choose to initialize the IOMMU after the virtio-pci which lead a wrong address space is returned during device plugged. So this patch switch to use transport specific way via iommu_enabled() to detect the IOMMU during vhost start. In this case, we are fine since we know the IOMMU is initialized correctly. Signed-off-by: Jason Wang --- hw/virtio/vhost.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c index 7b7bde7657..d2097b7423 100644 --- a/hw/virtio/vhost.c +++ b/hw/virtio/vhost.c @@ -286,7 +286,7 @@ static int vhost_dev_has_iommu(struct vhost_dev *dev) * 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 && + return virtio_bus_device_iommu_enabled(vdev) && virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM); } =20 --=20 2.25.1