From patchwork Thu Sep 5 04:22:13 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Shawn Anastasio X-Patchwork-Id: 11132101 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 809C013B1 for ; Thu, 5 Sep 2019 04:32:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6198F2080C for ; Thu, 5 Sep 2019 04:32:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=anastas.io header.i=@anastas.io header.b="OZFbCn8M" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725935AbfIEEcR (ORCPT ); Thu, 5 Sep 2019 00:32:17 -0400 Received: from alpha.anastas.io ([104.248.188.109]:33281 "EHLO alpha.anastas.io" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726097AbfIEEcR (ORCPT ); Thu, 5 Sep 2019 00:32:17 -0400 Received: from authenticated-user (alpha.anastas.io [104.248.188.109]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by alpha.anastas.io (Postfix) with ESMTPSA id B366F7F36F; Wed, 4 Sep 2019 23:22:36 -0500 (CDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=anastas.io; s=mail; t=1567657357; bh=K6Ul0Tf6WBGzJ3DDSMKISfwTd9Ljf7uLpT71uwUiykg=; h=From:To:Cc:Subject:Date:From; b=OZFbCn8M3hBjC8mHFPqH+pxxDD0whlm+XYT+LQWGi/JbN4iE5ONkE1ZWaUvPp9v8z xRyRe4ukehqLk2vBr3OKyu8ECMmNamJgCaHX6u9MXkIuoOo4OorTrZGyGNMr+DKxRe Zyt81X1TreZRBFNYDinjUIOzvoIBecFVwyLDQlET1cv722hifFvHKu22ZTalQG7c8/ mxrJyo/gWlvWh3lRiAtx+KJ280OdyM9ODQMv540j/pMeJBajW0YnuK9fUMOCfL5kYs NbzrH/z0/JOYam2OKUkTPA8LuxMdnS34dlanNTy/0OCWv1pdrMJV/fiVlJzdaSbIhG MSKjGjbqi2Ynw== From: Shawn Anastasio To: linux-pci@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Cc: bhelgaas@google.com, mpe@ellerman.id.au, aik@ozlabs.ru, benh@kernel.crashing.org, sbobroff@linux.ibm.com, oohall@gmail.com Subject: [PATCH 0/2] Fix IOMMU setup for hotplugged devices on pseries Date: Wed, 4 Sep 2019 23:22:13 -0500 Message-Id: <20190905042215.3974-1-shawn@anastas.io> MIME-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On pseries QEMU guests, IOMMU setup for hotplugged PCI devices is currently broken for all but the first device on a given bus. The culprit is an ordering issue in the pseries hotplug path (via pci_rescan_bus()) which results in IOMMU group assigment occuring before device registration in sysfs. This triggers the following check in arch/powerpc/kernel/iommu.c: /* * The sysfs entries should be populated before * binding IOMMU group. If sysfs entries isn't * ready, we simply bail. */ if (!device_is_registered(dev)) return -ENOENT; This fails for hotplugged devices since the pcibios_add_device() call in the pseries hotplug path (in pci_device_add()) occurs before device_add(). Since the IOMMU groups are set up in pcibios_add_device(), this means that a sysfs entry will not yet be present and it will fail. There is a special case that allows the first hotplugged device on a bus to succeed, though. The powerpc pcibios_add_device() implementation will skip initializing the device if bus setup is not yet complete. Later, the pci core will call pcibios_fixup_bus() which will perform setup for the first (and only) device on the bus and since it has already been registered in sysfs, the IOMMU setup will succeed. My current solution is to introduce another pcibios function, pcibios_fixup_dev, which is called after device_add() in pci_device_add(). Then in powerpc code, pcibios_setup_device() was moved from pcibios_add_device() to this new function which will occur after sysfs registration so IOMMU assignment will succeed. I added a new pcibios function rather than moving the pcibios_add_device() call to after the device_add() call in pci_add_device() because there are other architectures that use it and it wasn't immediately clear to me whether moving it would break them. If anybody has more insight or a better way to fix this, please let me know. Shawn Anastasio (2): PCI: Introduce pcibios_fixup_dev() powerpc/pci: Fix IOMMU setup for hotplugged devices on pseries arch/powerpc/kernel/pci-common.c | 13 ++++++------- drivers/pci/probe.c | 14 ++++++++++++++ include/linux/pci.h | 1 + 3 files changed, 21 insertions(+), 7 deletions(-)