From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755150AbdJISsK (ORCPT ); Mon, 9 Oct 2017 14:48:10 -0400 Received: from mga06.intel.com ([134.134.136.31]:16711 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754231AbdJISsJ (ORCPT ); Mon, 9 Oct 2017 14:48:09 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.42,501,1500966000"; d="scan'208";a="1180270647" Date: Mon, 9 Oct 2017 11:50:45 -0700 From: Jacob Pan To: Jean-Philippe Brucker Cc: "iommu@lists.linux-foundation.org" , LKML , Joerg Roedel , David Woodhouse , Greg Kroah-Hartman , Rafael Wysocki , "Liu, Yi L" , Lan Tianyu , "Tian, Kevin" , Raj Ashok , Alex Williamson , jacob.jun.pan@linux.intel.com Subject: Re: [PATCH v2 10/16] iommu: introduce device fault report API Message-ID: <20171009115045.17c9f031@jacob-builder> In-Reply-To: <5103e49c-d74c-c697-b5f7-e5c54edce595@arm.com> References: <1507244624-39189-1-git-send-email-jacob.jun.pan@linux.intel.com> <1507244624-39189-11-git-send-email-jacob.jun.pan@linux.intel.com> <5103e49c-d74c-c697-b5f7-e5c54edce595@arm.com> Organization: OTC X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 6 Oct 2017 10:36:02 +0100 Jean-Philippe Brucker wrote: > Hi Jacob, > > On 06/10/17 00:03, Jacob Pan wrote: > > Traditionally, device specific faults are detected and handled > > within their own device drivers. When IOMMU is enabled, faults such > > as DMA related transactions are detected by IOMMU. There is no > > generic reporting mechanism to report faults back to the in-kernel > > device driver or the guest OS in case of assigned devices. > > > > Faults detected by IOMMU is based on the transaction's source ID > > which can be reported at per device basis, regardless of the device > > type is a PCI device or not. > > > > The fault types include recoverable (e.g. page request) and > > unrecoverable faults(e.g. access error). In most cases, faults can > > be handled by IOMMU drivers internally. The primary use cases are as > > follows: > > 1. page request fault originated from an SVM capable device that is > > assigned to guest via vIOMMU. In this case, the first level page > > tables are owned by the guest. Page request must be propagated to > > the guest to let guest OS fault in the pages then send page > > response. In this mechanism, the direct receiver of IOMMU fault > > notification is VFIO, which can relay notification events to QEMU > > or other user space software. > > > > 2. faults need more subtle handling by device drivers. Other than > > simply invoke reset function, there are needs to let device driver > > handle the fault with a smaller impact. > > > > This patchset is intended to create a generic fault report API such > > that it can scale as follows: > > - all IOMMU types > > - PCI and non-PCI devices > > - recoverable and unrecoverable faults > > - VFIO and other other in kernel users > > - DMA & IRQ remapping (TBD) > > The original idea was brought up by David Woodhouse and discussions > > summarized at https://lwn.net/Articles/608914/. > > > > Signed-off-by: Jacob Pan > > Signed-off-by: Ashok Raj > > --- > [...] > > +int iommu_register_device_fault_handler(struct device *dev, > > + iommu_dev_fault_handler_t > > handler) +{ > > + if (dev->iommu_fault_param) > > + return -EBUSY; > > + get_device(dev); > > + dev->iommu_fault_param = > > + kzalloc(sizeof(struct iommu_fault_param), > > GFP_KERNEL); > > + if (!dev->iommu_fault_param) > > + return -ENOMEM; > > + dev->iommu_fault_param->dev_fault_handler = handler; > > Since the handler is owned by a device driver, you also need to clean > it up when switching the driver (native->VFIO and VFIO->native), in > iommu_attach_device I suppose. > I was thinking the driver who registered fault handler shall be held accountable to unregister. e.g. User must unbind driver (unregister fault handler included) before assigning device to vfio-pci. Otherwise, VFIO call to register handler would fail. I am assuming VFIO needs to have a separate device fault handler of its own. Jacob