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=-6.8 required=3.0 tests=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 564E5C31E45 for ; Thu, 13 Jun 2019 15:30:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2BB4120B7C for ; Thu, 13 Jun 2019 15:30:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728145AbfFMPaw (ORCPT ); Thu, 13 Jun 2019 11:30:52 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42346 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728666AbfFMLIV (ORCPT ); Thu, 13 Jun 2019 07:08:21 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 2FEA22F8BC8; Thu, 13 Jun 2019 11:08:21 +0000 (UTC) Received: from localhost (dhcp-192-222.str.redhat.com [10.33.192.222]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A203660BE2; Thu, 13 Jun 2019 11:08:18 +0000 (UTC) From: Cornelia Huck To: Sebastian Ott , Peter Oberparleiter Cc: Halil Pasic , Alex Williamson , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Cornelia Huck Subject: [PATCH] s390/cio: introduce driver_override on the css bus Date: Thu, 13 Jun 2019 13:08:15 +0200 Message-Id: <20190613110815.17251-1-cohuck@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Thu, 13 Jun 2019 11:08:21 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Sometimes, we want to control which of the matching drivers binds to a subchannel device (e.g. for subchannels we want to handle via vfio-ccw). For pci devices, a mechanism to do so has been introduced in 782a985d7af2 ("PCI: Introduce new device binding path using pci_dev.driver_override"). It makes sense to introduce the driver_override attribute for subchannel devices as well, so that we can easily extend the 'driverctl' tool (which makes use of the driver_override attribute for pci). Note that unlike pci we still require a driver override to match the subchannel type; matching more than one subchannel type is probably not useful anyway. Signed-off-by: Cornelia Huck --- Lightly tested; did not yet attempt to adapt driverctl to actually make use of it. For some background, refer to the thread around https://lore.kernel.org/kvm/20190612091439.3a33f17b.cohuck@redhat.com/ --- Documentation/ABI/testing/sysfs-bus-css | 23 +++++++++++ drivers/s390/cio/cio.h | 1 + drivers/s390/cio/css.c | 53 +++++++++++++++++++++++++ 3 files changed, 77 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-bus-css b/Documentation/ABI/testing/sysfs-bus-css index 2979c40c10e9..966f8504bd7b 100644 --- a/Documentation/ABI/testing/sysfs-bus-css +++ b/Documentation/ABI/testing/sysfs-bus-css @@ -33,3 +33,26 @@ Description: Contains the PIM/PAM/POM values, as reported by the in sync with the values current in the channel subsystem). Note: This is an I/O-subchannel specific attribute. Users: s390-tools, HAL + +What: /sys/bus/css/devices/.../driver_override +Date: June 2019 +Contact: Cornelia Huck + linux-s390@vger.kernel.org +Description: This file allows the driver for a device to be specified. When + specified, only a driver with a name matching the value written + to driver_override will have an opportunity to bind to the + device. The override is specified by writing a string to the + driver_override file (echo vfio-ccw > driver_override) and + may be cleared with an empty string (echo > driver_override). + This returns the device to standard matching rules binding. + Writing to driver_override does not automatically unbind the + device from its current driver or make any attempt to + automatically load the specified driver. If no driver with a + matching name is currently loaded in the kernel, the device + will not bind to any driver. This also allows devices to + opt-out of driver binding using a driver_override name such as + "none". Only a single driver may be specified in the override, + there is no support for parsing delimiters. + Note that unlike the mechanism of the same name for pci, this + file does not allow to override basic matching rules. I.e., + the driver must still match the subchannel type of the device. diff --git a/drivers/s390/cio/cio.h b/drivers/s390/cio/cio.h index 06a91743335a..8c4af88f1ac3 100644 --- a/drivers/s390/cio/cio.h +++ b/drivers/s390/cio/cio.h @@ -113,6 +113,7 @@ struct subchannel { enum sch_todo todo; struct work_struct todo_work; struct schib_config config; + char *driver_override; /* Driver name to force a match */ } __attribute__ ((aligned(8))); DECLARE_PER_CPU_ALIGNED(struct irb, cio_irb); diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c index aea502922646..f3436a17e3b5 100644 --- a/drivers/s390/cio/css.c +++ b/drivers/s390/cio/css.c @@ -165,6 +165,7 @@ static void css_subchannel_release(struct device *dev) sch->config.intparm = 0; cio_commit_config(sch); + kfree(sch->driver_override); kfree(sch->lock); kfree(sch); } @@ -315,9 +316,57 @@ static ssize_t modalias_show(struct device *dev, struct device_attribute *attr, static DEVICE_ATTR_RO(modalias); +static ssize_t driver_override_store(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t count) +{ + struct subchannel *sch = to_subchannel(dev); + char *driver_override, *old, *cp; + + /* We need to keep extra room for a newline */ + if (count >= (PAGE_SIZE - 1)) + return -EINVAL; + + driver_override = kstrndup(buf, count, GFP_KERNEL); + if (!driver_override) + return -ENOMEM; + + cp = strchr(driver_override, '\n'); + if (cp) + *cp = '\0'; + + device_lock(dev); + old = sch->driver_override; + if (strlen(driver_override)) { + sch->driver_override = driver_override; + } else { + kfree(driver_override); + sch->driver_override = NULL; + } + device_unlock(dev); + + kfree(old); + + return count; +} + +static ssize_t driver_override_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct subchannel *sch = to_subchannel(dev); + ssize_t len; + + device_lock(dev); + len = snprintf(buf, PAGE_SIZE, "%s\n", sch->driver_override); + device_unlock(dev); + return len; +} +static DEVICE_ATTR_RW(driver_override); + static struct attribute *subch_attrs[] = { &dev_attr_type.attr, &dev_attr_modalias.attr, + &dev_attr_driver_override.attr, NULL, }; @@ -1222,6 +1271,10 @@ static int css_bus_match(struct device *dev, struct device_driver *drv) struct css_driver *driver = to_cssdriver(drv); struct css_device_id *id; + /* When driver_override is set, only bind to the matching driver */ + if (sch->driver_override && strcmp(sch->driver_override, drv->name)) + return 0; + for (id = driver->subchannel_type; id->match_flags; id++) { if (sch->st == id->type) return 1; -- 2.20.1