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=-14.8 required=3.0 tests=BAYES_00, DATE_IN_FUTURE_06_12,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 5EA93C433E0 for ; Tue, 2 Mar 2021 12:37:35 +0000 (UTC) Received: from smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (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 F08AA64F3D for ; Tue, 2 Mar 2021 12:37:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F08AA64F3D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.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 smtp2.osuosl.org (Postfix) with ESMTP id 9FAE243166; Tue, 2 Mar 2021 12:37:34 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id GGIO6Ch4OYWh; Tue, 2 Mar 2021 12:37:33 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp2.osuosl.org (Postfix) with ESMTP id 64BC94315D; Tue, 2 Mar 2021 12:37:33 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 431B8C000A; Tue, 2 Mar 2021 12:37:33 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 54655C0001 for ; Tue, 2 Mar 2021 12:37:32 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 35BAA83F3F for ; Tue, 2 Mar 2021 12:37:32 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id g1AWvdD7rFWC for ; Tue, 2 Mar 2021 12:37:31 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by smtp1.osuosl.org (Postfix) with ESMTPS id 2BAAF83F38 for ; Tue, 2 Mar 2021 12:37:31 +0000 (UTC) IronPort-SDR: WBa13MwWMXAFOtcd0mRNh/mziBi+ivwr3L9kHcOIbeBmaCowr3jbXdmAgxFWmm3IGilP1OtsSL uxBDHPtd+PLA== X-IronPort-AV: E=McAfee;i="6000,8403,9910"; a="166675210" X-IronPort-AV: E=Sophos;i="5.81,216,1610438400"; d="scan'208";a="166675210" Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Mar 2021 04:37:30 -0800 IronPort-SDR: +bnqDXtZjncSG44eBre9yQ1J3gqP/VB8tzZfP4kWU5t71DypcRw0wyIkYZ2r573PuPSL9leJxx Q96lIiyp2U2g== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.81,216,1610438400"; d="scan'208";a="427472182" Received: from yiliu-dev.bj.intel.com (HELO dual-ub.bj.intel.com) ([10.238.156.135]) by fmsmga004.fm.intel.com with ESMTP; 02 Mar 2021 04:37:26 -0800 From: Liu Yi L To: alex.williamson@redhat.com, eric.auger@redhat.com, baolu.lu@linux.intel.com, joro@8bytes.org Subject: [Patch v8 09/10] vfio: Document dual stage control Date: Wed, 3 Mar 2021 04:35:44 +0800 Message-Id: <20210302203545.436623-10-yi.l.liu@intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210302203545.436623-1-yi.l.liu@intel.com> References: <20210302203545.436623-1-yi.l.liu@intel.com> MIME-Version: 1.0 Cc: jean-philippe@linaro.org, kevin.tian@intel.com, ashok.raj@intel.com, kvm@vger.kernel.org, stefanha@gmail.com, jun.j.tian@intel.com, Stefan Hajnoczi , iommu@lists.linux-foundation.org, vivek.gautam@arm.com, yi.y.sun@intel.com, jgg@nvidia.com, Lingshan.Zhu@intel.com, jasowang@redhat.com, hao.wu@intel.com 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" From: Eric Auger The VFIO API was enhanced to support nested stage control: a bunch of new ioctls and usage guideline. Let's document the process to follow to set up nested mode. Cc: Kevin Tian CC: Jacob Pan Cc: Alex Williamson Cc: Eric Auger Cc: Jean-Philippe Brucker Cc: Joerg Roedel Cc: Lu Baolu Signed-off-by: Eric Auger Signed-off-by: Liu Yi L Reviewed-by: Stefan Hajnoczi --- v7 -> v8: *) remove SYSWIDE_PASID description, point to /dev/ioasid when mentioning PASID allocation from host. v6 -> v7: *) tweak per Eric's comments. v5 -> v6: *) tweak per Eric's comments. v3 -> v4: *) add review-by from Stefan Hajnoczi v2 -> v3: *) address comments from Stefan Hajnoczi v1 -> v2: *) new in v2, compared with Eric's original version, pasid table bind and fault reporting is removed as this series doesn't cover them. Original version from Eric. https://lore.kernel.org/kvm/20200320161911.27494-12-eric.auger@redhat.com/ --- Documentation/driver-api/vfio.rst | 77 +++++++++++++++++++++++++++++++ 1 file changed, 77 insertions(+) diff --git a/Documentation/driver-api/vfio.rst b/Documentation/driver-api/vfio.rst index f1a4d3c3ba0b..9ccf9d63b72f 100644 --- a/Documentation/driver-api/vfio.rst +++ b/Documentation/driver-api/vfio.rst @@ -239,6 +239,83 @@ group and can access them as follows:: /* Gratuitous device reset and go... */ ioctl(device, VFIO_DEVICE_RESET); +IOMMU Dual Stage Control +------------------------ + +Some IOMMUs support 2 stages/levels of translation. Stage corresponds +to the ARM terminology while level corresponds to Intel's terminology. +In the following text, we use either without distinction. + +This is useful when the guest is exposed with a virtual IOMMU and some +devices are assigned to the guest through VFIO. Then the guest OS can +use stage-1 (GIOVA -> GPA or GVA->GPA), while the hypervisor uses stage +2 for VM isolation (GPA -> HPA). + +Under dual-stage translation, the guest gets ownership of the stage-1 +page tables or both the stage-1 configuration structures and page tables. +This depends on vendor. e.g. on Intel platform, the guest owns stage-1 +page tables under nesting. While on ARM, the guest owns both the stage-1 +configuration structures and page tables under nesting. The hypervisor +owns the root configuration structure (for security reasons), including +stage-2 configuration. This works as long as configuration structures +and page table formats are compatible between the virtual IOMMU and the +physical IOMMU. + +Assuming the HW supports it, this nested mode is selected by choosing the +VFIO_TYPE1_NESTING_IOMMU type through: + + ioctl(container, VFIO_SET_IOMMU, VFIO_TYPE1_NESTING_IOMMU); + +This forces the hypervisor to use the stage-2, leaving stage-1 available +for guest usage. +The stage-1 format and binding method are reported in nesting capability. +(VFIO_IOMMU_TYPE1_INFO_CAP_NESTING) through VFIO_IOMMU_GET_INFO: + + ioctl(container->fd, VFIO_IOMMU_GET_INFO, &nesting_info); + +The nesting cap info is available only after NESTING_IOMMU is selected. +If the underlying IOMMU doesn't support nesting, VFIO_SET_IOMMU fails and +userspace should try other IOMMU types. Details of the nesting cap info +can be found in Documentation/userspace-api/iommu.rst. + +Bind stage-1 page table to the IOMMU differs per platform. On Intel, +the stage1 page table info are mediated by the userspace for each PASID. +On ARM, the userspace directly passes the GPA of the whole PASID table. +Currently only Intel's binding is supported (IOMMU_NESTING_FEAT_BIND_PGTBL) +is supported: + + nesting_op->flags = VFIO_IOMMU_NESTING_OP_BIND_PGTBL; + memcpy(&nesting_op->data, &bind_data, sizeof(bind_data)); + ioctl(container->fd, VFIO_IOMMU_NESTING_OP, nesting_op); + +When multiple stage-1 page tables are supported on a device, each page +table is associated with a PASID (Process Address Space ID) to differentiate +with each other. In such case, userspace should include PASID in the +bind_data when issuing direct binding requests. + +PASID could be managed per-device or system-wide which, again, depends on +IOMMU vendor. e.g. as by Intel platforms, userspace *must* allocate PASID +from host before attempting binding of stage-1 page table, the allocation +is done by the /dev/ioasid interface. For systems without /dev/ioasid, +userspace should not go further binding page table and shall be failed +by the kernel. For the usage of /dev/ioasid, please refer to below doc: + + Documentation/userspace-api/ioasid.rst + +Once the stage-1 page table is bound to the IOMMU, the guest is allowed to +fully manage its mapping at its disposal. The IOMMU walks nested stage-1 +and stage-2 page tables when serving DMA requests from assigned device, and +may cache the stage-1 mapping in the IOTLB. When required (IOMMU_NESTING_ +FEAT_CACHE_INVLD), userspace *must* forward guest stage-1 invalidation to +the host, so the IOTLB is invalidated: + + nesting_op->flags = VFIO_IOMMU_NESTING_OP_CACHE_INVLD; + memcpy(&nesting_op->data, &cache_inv_data, sizeof(cache_inv_data)); + ioctl(container->fd, VFIO_IOMMU_NESTING_OP, nesting_op); + +Forwarded invalidations can happen at various granularity levels (page +level, context level, etc.) + VFIO User API ------------------------------------------------------------------------------- -- 2.25.1 _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu