From patchwork Tue Nov 16 15:34:33 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: =?utf-8?q?=C5=81ukasz_Gieryk?= X-Patchwork-Id: 12622775 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 97521C433FE for ; Tue, 16 Nov 2021 15:54:38 +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 2F8AF61BF5 for ; Tue, 16 Nov 2021 15:54:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 2F8AF61BF5 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:39822 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mn0n7-0007yJ-3V for qemu-devel@archiver.kernel.org; Tue, 16 Nov 2021 10:54:37 -0500 Received: from eggs.gnu.org ([209.51.188.92]:42746) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mn0lc-0005Vl-6N; Tue, 16 Nov 2021 10:53:04 -0500 Received: from mga04.intel.com ([192.55.52.120]:64383) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mn0la-0007ek-GM; Tue, 16 Nov 2021 10:53:03 -0500 X-IronPort-AV: E=McAfee;i="6200,9189,10169"; a="232438843" X-IronPort-AV: E=Sophos;i="5.87,239,1631602800"; d="scan'208";a="232438843" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Nov 2021 07:52:59 -0800 X-IronPort-AV: E=Sophos;i="5.87,239,1631602800"; d="scan'208";a="454494332" Received: from lgieryk-lnx.igk.intel.com ([172.22.230.153]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Nov 2021 07:52:57 -0800 From: =?utf-8?q?=C5=81ukasz_Gieryk?= To: qemu-devel@nongnu.org Subject: [PATCH v2 02/15] pcie: Add some SR/IOV API documentation in docs/pcie_sriov.txt Date: Tue, 16 Nov 2021 16:34:33 +0100 Message-Id: <20211116153446.317143-3-lukasz.gieryk@linux.intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20211116153446.317143-1-lukasz.gieryk@linux.intel.com> References: <20211116153446.317143-1-lukasz.gieryk@linux.intel.com> MIME-Version: 1.0 Organization: Intel Technology Poland sp. z o.o. - ul. Slowackiego 173, 80-298 Gdansk - KRS 101882 - NIP 957-07-52-316 Received-SPF: none client-ip=192.55.52.120; envelope-from=lukasz.gieryk@linux.intel.com; helo=mga04.intel.com X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_NONE=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-block@nongnu.org, "Michael S. Tsirkin" , =?utf-8?q?=C5=81ukasz_Gieryk?= , Lukasz Maniak , Knut Omang Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Knut Omang Add a small intro + minimal documentation for how to implement SR/IOV support for an emulated device. Signed-off-by: Knut Omang --- docs/pcie_sriov.txt | 115 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 115 insertions(+) create mode 100644 docs/pcie_sriov.txt diff --git a/docs/pcie_sriov.txt b/docs/pcie_sriov.txt new file mode 100644 index 0000000000..f5e891e1d4 --- /dev/null +++ b/docs/pcie_sriov.txt @@ -0,0 +1,115 @@ +PCI SR/IOV EMULATION SUPPORT +============================ + +Description +=========== +SR/IOV (Single Root I/O Virtualization) is an optional extended capability +of a PCI Express device. It allows a single physical function (PF) to appear as multiple +virtual functions (VFs) for the main purpose of eliminating software +overhead in I/O from virtual machines. + +Qemu now implements the basic common functionality to enable an emulated device +to support SR/IOV. Yet no fully implemented devices exists in Qemu, but a +proof-of-concept hack of the Intel igb can be found here: + +git://github.com/knuto/qemu.git sriov_patches_v5 + +Implementation +============== +Implementing emulation of an SR/IOV capable device typically consists of +implementing support for two types of device classes; the "normal" physical device +(PF) and the virtual device (VF). From Qemu's perspective, the VFs are just +like other devices, except that some of their properties are derived from +the PF. + +A virtual function is different from a physical function in that the BAR +space for all VFs are defined by the BAR registers in the PFs SR/IOV +capability. All VFs have the same BARs and BAR sizes. + +Accesses to these virtual BARs then is computed as + + + * + + +From our emulation perspective this means that there is a separate call for +setting up a BAR for a VF. + +1) To enable SR/IOV support in the PF, it must be a PCI Express device so + you would need to add a PCI Express capability in the normal PCI + capability list. You might also want to add an ARI (Alternative + Routing-ID Interpretation) capability to indicate that your device + supports functions beyond it's "own" function space (0-7), + which is necessary to support more than 7 functions, or + if functions extends beyond offset 7 because they are placed at an + offset > 1 or have stride > 1. + + ... + #include "hw/pci/pcie.h" + #include "hw/pci/pcie_sriov.h" + + pci_your_pf_dev_realize( ... ) + { + ... + int ret = pcie_endpoint_cap_init(d, 0x70); + ... + pcie_ari_init(d, 0x100, 1); + ... + + /* Add and initialize the SR/IOV capability */ + pcie_sriov_pf_init(d, 0x200, "your_virtual_dev", + vf_devid, initial_vfs, total_vfs, + fun_offset, stride); + + /* Set up individual VF BARs (parameters as for normal BARs) */ + pcie_sriov_pf_init_vf_bar( ... ) + ... + } + + For cleanup, you simply call: + + pcie_sriov_pf_exit(device); + + which will delete all the virtual functions and associated resources. + +2) Similarly in the implementation of the virtual function, you need to + make it a PCI Express device and add a similar set of capabilities + except for the SR/IOV capability. Then you need to set up the VF BARs as + subregions of the PFs SR/IOV VF BARs by calling + pcie_sriov_vf_register_bar() instead of the normal pci_register_bar() call: + + pci_your_vf_dev_realize( ... ) + { + ... + int ret = pcie_endpoint_cap_init(d, 0x60); + ... + pcie_ari_init(d, 0x100, 1); + ... + memory_region_init(mr, ... ) + pcie_sriov_vf_register_bar(d, bar_nr, mr); + ... + } + +Testing on Linux guest +====================== +The easiest is if your device driver supports sysfs based SR/IOV +enabling. Support for this was added in kernel v.3.8, so not all drivers +support it yet. + +To enable 4 VFs for a device at 01:00.0: + + modprobe yourdriver + echo 4 > /sys/bus/pci/devices/0000:01:00.0/sriov_numvfs + +You should now see 4 VFs with lspci. +To turn SR/IOV off again - the standard requires you to turn it off before you can enable +another VF count, and the emulation enforces this: + + echo 0 > /sys/bus/pci/devices/0000:01:00.0/sriov_numvfs + +Older drivers typically provide a max_vfs module parameter +to enable it at load time: + + modprobe yourdriver max_vfs=4 + +To disable the VFs again then, you simply have to unload the driver: + + rmmod yourdriver