From patchwork Mon Apr 13 05:55:04 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Yan Zhao X-Patchwork-Id: 11485057 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 29D31913 for ; Mon, 13 Apr 2020 06:04:53 +0000 (UTC) Received: from vger.kernel.org (unknown [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0124020774 for ; Mon, 13 Apr 2020 06:04:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0124020774 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=kvm-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728113AbgDMGEu (ORCPT ); Mon, 13 Apr 2020 02:04:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.18]:46692 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726967AbgDMGEu (ORCPT ); Mon, 13 Apr 2020 02:04:50 -0400 Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D0ED6C0A3BE0; Sun, 12 Apr 2020 23:04:49 -0700 (PDT) IronPort-SDR: xew7+1M5hZo4DQXrcmLbPJyzWzW6RmhPfJUzG9bZ9CGYP8B2fK9ivnNAvkIQyTNQdoNKm89u2p 2iDJYQ+yhvHQ== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Apr 2020 23:04:49 -0700 IronPort-SDR: MbFwKnGaaMwEyGnfsS5ROLnyX35cXTl0aIVx4vYCD8SaZ6Q+Nm5+ioJ8P7BmoI3lVcpfUdSGfE s40BgPxp5wWw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,377,1580803200"; d="scan'208";a="245065840" Received: from joy-optiplex-7040.sh.intel.com ([10.239.13.16]) by fmsmga008.fm.intel.com with ESMTP; 12 Apr 2020 23:04:43 -0700 From: Yan Zhao To: intel-gvt-dev@lists.freedesktop.org Cc: libvir-list@redhat.com, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, aik@ozlabs.ru, Zhengxiao.zx@alibaba-inc.com, shuangtai.tst@alibaba-inc.com, qemu-devel@nongnu.org, eauger@redhat.com, yi.l.liu@intel.com, xin.zeng@intel.com, ziye.yang@intel.com, mlevitsk@redhat.com, pasic@linux.ibm.com, felipe@nutanix.com, changpeng.liu@intel.com, Ken.Xue@amd.com, jonathan.davies@nutanix.com, shaopeng.he@intel.com, alex.williamson@redhat.com, eskultet@redhat.com, dgilbert@redhat.com, cohuck@redhat.com, kevin.tian@intel.com, zhenyuw@linux.intel.com, zhi.a.wang@intel.com, cjia@nvidia.com, kwankhede@nvidia.com, berrange@redhat.com, dinechin@redhat.com, corbet@lwn.net, Yan Zhao Subject: [PATCH v5 3/4] vfio/mdev: add migration_version attribute for mdev (under mdev device node) Date: Mon, 13 Apr 2020 01:55:04 -0400 Message-Id: <20200413055504.27311-1-yan.y.zhao@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200413055201.27053-1-yan.y.zhao@intel.com> References: <20200413055201.27053-1-yan.y.zhao@intel.com> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org migration_version attribute is used to check migration compatibility between two mdev devices of the same mdev type. The key is that it's rw and its data is opaque to userspace. Userspace reads migration_version of mdev device at source side and writes the value to migration_version attribute of mdev device at target side. It judges migration compatibility according to whether the read and write operations succeed or fail. Currently, it is able to read/write migration_version attribute under two places: (1) under mdev_type node userspace is able to know whether two mdev devices are compatible before a mdev device is created. userspace also needs to check whether the two mdev devices are of the same mdev type before checking the migration_version attribute. It also needs to check device creation parameters if aggregation is supported in future. (2) under mdev device node userspace is able to know whether two mdev devices are compatible after they are all created. But it does not need to check mdev type and device creation parameter for aggregation as device vendor driver would have incorporated those information into the migration_version attribute. __ userspace /\ \ / \write / read \ ________/__________ ___\|/_____________ | migration_version | | migration_version |-->check migration --------------------- --------------------- compatibility mdev device A mdev device B This patch is for mdev documentation about the second place (under mdev device node) Cc: Alex Williamson Cc: Erik Skultety Cc: "Dr. David Alan Gilbert" Cc: Cornelia Huck Cc: "Tian, Kevin" Cc: Zhenyu Wang Cc: "Wang, Zhi A" Cc: Neo Jia Cc: Kirti Wankhede Cc: Daniel P. Berrangé Cc: Christophe de Dinechin Signed-off-by: Yan Zhao --- .../driver-api/vfio-mediated-device.rst | 70 +++++++++++++++++++ 1 file changed, 70 insertions(+) diff --git a/Documentation/driver-api/vfio-mediated-device.rst b/Documentation/driver-api/vfio-mediated-device.rst index 2d1f3c0f3c8f..efbadfd51b7e 100644 --- a/Documentation/driver-api/vfio-mediated-device.rst +++ b/Documentation/driver-api/vfio-mediated-device.rst @@ -383,6 +383,7 @@ Directories and Files Under the sysfs for Each mdev Device |--- remove |--- mdev_type {link to its type} |--- vendor-specific-attributes [optional] + |--- migration_verion [optional] * remove (write only) @@ -394,6 +395,75 @@ Example:: # echo 1 > /sys/bus/mdev/devices/$mdev_UUID/remove +* migration_version (rw, optional) + It is used to check migration compatibility between two mdev devices. + Absence of this attribute means the mdev device does not support migration. + + This attribute provides a way to check migration compatibility between two + mdev devices from userspace after device created. The intended usage is + for userspace to read the migration_version attribute from one mdev device and + then writing that value to the migration_version attribute of the other mdev + device. The second mdev device indicates compatibility via the return code of + the write operation. This makes compatibility between mdev devices completely + vendor-defined and opaque to userspace. Userspace should do nothing more + than use the migration_version attribute to confirm source to target + compatibility. + + Reading/Writing Attribute Data: + read(2) will fail if a mdev device does not support migration and otherwise + succeed and return migration_version string of the mdev device. + + This migration_version string is vendor defined and opaque to the + userspace. Vendor is free to include whatever they feel is relevant. + e.g. -. + + Restrictions on this migration_version string: + 1. It should only contain ascii characters + 2. MAX Length is PATH_MAX (4096) + + write(2) expects migration_version string of source mdev device, and will + succeed if it is determined to be compatible and otherwise fail with + vendor specific errno. + + Errno: + -An errno on read(2) indicates the mdev devicedoes not support migration; + -An errno on write(2) indicates the mdev devices are incompatible or the + target doesn't support migration. + Vendor driver is free to define specific errno and is suggested to + print detailed error in syslog for diagnose purpose. + + Userspace should treat ANY of below conditions as two mdev devices not + compatible: + (1) any one of the two mdev devices does not have a migration_version + attribute + (2) error when reading from migration_version attribute of one mdev device + (3) error when writing migration_version string of one mdev device to + migration_version attribute of the other mdev device + + Userspace should regard two mdev devices compatible when ALL of below + conditions are met: + (1) success when reading from migration_version attribute of one mdev device. + (2) success when writing migration_version string of one mdev device to + migration_version attribute of the other mdev device. + + Example Usage: + (1) Retrieve the mdev source migration_version: + + # cat /sys/bus/mdev/devices/$mdev_UUID1/migration_version + + If reading the source migration_version generates an error, migration is not + possible. + + (2) Test source migration_version at target: + + Given a migration_version as outlined above, its compatibility to an + instantiated device of the same mdev type can be tested as: + # echo $VERSION > /sys/bus/mdev/devices/$mdev_UUID2/migration_version + + If this write fails, the source and target migration versions are not + compatible or the target does not support migration. + + Mediated device Hot plug ------------------------