From patchwork Fri Sep 16 20:44:48 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Alex Williamson X-Patchwork-Id: 12978839 X-Patchwork-Delegate: bhelgaas@google.com 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0B689ECAAA1 for ; Fri, 16 Sep 2022 20:44:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229515AbiIPUo4 (ORCPT ); Fri, 16 Sep 2022 16:44:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59034 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229861AbiIPUoz (ORCPT ); Fri, 16 Sep 2022 16:44:55 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B9B253C8DE for ; Fri, 16 Sep 2022 13:44:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1663361092; 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; bh=y/XvrfP+pTeDCxzR/xWcKMELylwPENiPm0YnxC8VazM=; b=Syyp7MrzhsoVxuBhuR+cYQqw3lllO1kTZt72oRAgpgglAdtykii31gC1M9EQciWZeyUNYj Qa7lqv7Jgc7aMV+K3XnYYruTilwqETUTF/ErZ8aASHU+NLRUnB58GHBFPHwp+fRZ4BztZB LV5T/5vm7C9MYqqPkgVef0TfYeavX5g= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-629-i4ZdB-brNsmBWM8zwFkeog-1; Fri, 16 Sep 2022 16:44:49 -0400 X-MC-Unique: i4ZdB-brNsmBWM8zwFkeog-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id E1BB2811E67; Fri, 16 Sep 2022 20:44:48 +0000 (UTC) Received: from [172.30.42.193] (unknown [10.22.8.99]) by smtp.corp.redhat.com (Postfix) with ESMTP id 74EB6492B04; Fri, 16 Sep 2022 20:44:48 +0000 (UTC) Subject: [PATCH v2] PCI: Expose PCIe Resizable BAR support via sysfs From: Alex Williamson To: linux-pci@vger.kernel.org Cc: =?utf-8?q?Christian_K=C3=B6nig?= , =?utf-8?q?K?= =?utf-8?q?rzysztof_Wilczy=C5=84ski?= , bhelgaas@google.com Date: Fri, 16 Sep 2022 14:44:48 -0600 Message-ID: <166336088796.3597940.14973499936692558556.stgit@omen> User-Agent: StGit/1.5.dev2+g9ce680a52bd9 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org This proposes a simple sysfs interface to Resizable BAR support, largely for the purposes of assigning such devices to a VM through VFIO. Resizable BARs present a difficult feature to expose to a VM through emulation, as resizing a BAR is done on the host. It can fail, and often does, but we have no means via emulation of a PCIe REBAR capability to handle the error cases. A vfio-pci specific ioctl interface is also cumbersome as there are often multiple devices within the same bridge aperture and handling them is a challenge. In the interface proposed here, expanding a BAR potentially requires such devices to be soft-removed during the resize operation and rescanned after, in order for all the necessary resources to be released. A pci-sysfs interface is also more universal than a vfio specific interface. Please see the ABI documentation update for usage. Cc: Christian König Cc: Krzysztof Wilczyński Signed-off-by: Alex Williamson Reviewed-by: Christian König --- v2: - Convert to static attributes with is_visible callback - Include aperture driver removal for console drivers - Remove and recreate resourceN attributes - Expand ABI description - Drop 2nd field in show attribute Documentation/ABI/testing/sysfs-bus-pci | 33 +++++++++ drivers/pci/pci-sysfs.c | 108 +++++++++++++++++++++++++++++++ 2 files changed, 141 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci index 6fc2c2efe8ab..ba9a5482436f 100644 --- a/Documentation/ABI/testing/sysfs-bus-pci +++ b/Documentation/ABI/testing/sysfs-bus-pci @@ -457,3 +457,36 @@ Description: The file is writable if the PF is bound to a driver that implements ->sriov_set_msix_vec_count(). + +What: /sys/bus/pci/devices/.../resourceN_resize +Date: September 2022 +Contact: Alex Williamson +Description: + These files provide an interface to PCIe Resizable BAR support. + A file is created for each BAR resource (N) supported by the + PCIe Resizable BAR extended capability of the device. Reading + each file exposes the bitmap of available resources sizes: + + # cat resource1_resize + 00000000000001c0 + + The bitmap represents supported resources sizes for the BAR, + where bit0 = 1MB, bit1 = 2MB, bit2 = 4MB, etc. In the above + example the devices supports 64MB, 128MB, and 256MB BAR sizes. + + When writing the file, the user provides the bit position of + the desired resource size, for example: + + # echo 7 > resource1_resize + + This indicates to set the size value corresponding to bit 7, + 128MB. The resulting size is 2 ^ (bit# + 20). This definition + matches the PCIe specification of this capability. + + In order to make use of resouce resizing, all PCI drivers must + be unbound from the device and peer devices under the same + parent bridge may need to be soft removed. In the case of + VGA devices, writing a resize value will remove low level + console drivers from the device. Raw users of pci-sysfs + resourceN attributes must be terminated prior to resizing. + Success of the resizing operation is not a guaranteed. diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index 9ac92e6a2397..f0298a8b08d9 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -28,6 +28,7 @@ #include #include #include +#include #include "pci.h" static int sysfs_initialized; /* = 0 */ @@ -1379,6 +1380,112 @@ static const struct attribute_group pci_dev_reset_attr_group = { .is_visible = pci_dev_reset_attr_is_visible, }; +#define pci_dev_resource_resize_attr(n) \ +static ssize_t resource##n##_resize_show(struct device *dev, \ + struct device_attribute *attr, \ + char * buf) \ +{ \ + struct pci_dev *pdev = to_pci_dev(dev); \ + ssize_t ret; \ + \ + pci_config_pm_runtime_get(pdev); \ + \ + ret = sysfs_emit(buf, "%016llx\n", \ + (u64)pci_rebar_get_possible_sizes(pdev, n)); \ + \ + pci_config_pm_runtime_put(pdev); \ + \ + return ret; \ +} \ + \ +static ssize_t resource##n##_resize_store(struct device *dev, \ + struct device_attribute *attr,\ + const char *buf, size_t count)\ +{ \ + struct pci_dev *pdev = to_pci_dev(dev); \ + unsigned long size, flags; \ + int ret, i; \ + u16 cmd; \ + \ + if (kstrtoul(buf, 0, &size) < 0) \ + return -EINVAL; \ + \ + device_lock(dev); \ + if (dev->driver) { \ + ret = -EBUSY; \ + goto unlock; \ + } \ + \ + pci_config_pm_runtime_get(pdev); \ + \ + if ((pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA) { \ + ret = aperture_remove_conflicting_pci_devices(pdev, \ + "resourceN_resize"); \ + if (ret) \ + goto pm_put; \ + } \ + \ + pci_read_config_word(pdev, PCI_COMMAND, &cmd); \ + pci_write_config_word(pdev, PCI_COMMAND, \ + cmd & ~PCI_COMMAND_MEMORY); \ + \ + flags = pci_resource_flags(pdev, n); \ + \ + pci_remove_resource_files(pdev); \ + \ + for (i = 0; i < PCI_STD_NUM_BARS; i++) { \ + if (pci_resource_len(pdev, i) && \ + pci_resource_flags(pdev, i) == flags) \ + pci_release_resource(pdev, i); \ + } \ + \ + ret = pci_resize_resource(pdev, n, size); \ + \ + pci_assign_unassigned_bus_resources(pdev->bus); \ + \ + if (pci_create_resource_files(pdev)) \ + pci_warn(pdev, "Failed to recreate resource files after BAR resizing\n");\ + \ + pci_write_config_word(pdev, PCI_COMMAND, cmd); \ +pm_put: \ + pci_config_pm_runtime_put(pdev); \ +unlock: \ + device_unlock(dev); \ + \ + return ret ? ret : count; \ +} \ +static DEVICE_ATTR_RW(resource##n##_resize) + +pci_dev_resource_resize_attr(0); +pci_dev_resource_resize_attr(1); +pci_dev_resource_resize_attr(2); +pci_dev_resource_resize_attr(3); +pci_dev_resource_resize_attr(4); +pci_dev_resource_resize_attr(5); + +static struct attribute *resource_resize_attrs[] = { + &dev_attr_resource0_resize.attr, + &dev_attr_resource1_resize.attr, + &dev_attr_resource2_resize.attr, + &dev_attr_resource3_resize.attr, + &dev_attr_resource4_resize.attr, + &dev_attr_resource5_resize.attr, + NULL, +}; + +static umode_t resource_resize_is_visible(struct kobject *kobj, + struct attribute *a, int n) +{ + struct pci_dev *pdev = to_pci_dev(kobj_to_dev(kobj)); + + return pci_rebar_get_current_size(pdev, n) < 0 ? 0 : a->mode; +} + +static const struct attribute_group pci_dev_resource_resize_group = { + .attrs = resource_resize_attrs, + .is_visible = resource_resize_is_visible, +}; + int __must_check pci_create_sysfs_dev_files(struct pci_dev *pdev) { if (!sysfs_initialized) @@ -1500,6 +1607,7 @@ const struct attribute_group *pci_dev_groups[] = { #ifdef CONFIG_ACPI &pci_dev_acpi_attr_group, #endif + &pci_dev_resource_resize_group, NULL, };