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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 CCE28C28CC5 for ; Wed, 5 Jun 2019 22:42:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AE1112083E for ; Wed, 5 Jun 2019 22:42:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726581AbfFEWmt (ORCPT ); Wed, 5 Jun 2019 18:42:49 -0400 Received: from mga18.intel.com ([134.134.136.126]:12498 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726510AbfFEWmt (ORCPT ); Wed, 5 Jun 2019 18:42:49 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Jun 2019 15:42:48 -0700 X-ExtLoop1: 1 Received: from jacob-builder.jf.intel.com (HELO jacob-builder) ([10.7.199.155]) by orsmga002.jf.intel.com with ESMTP; 05 Jun 2019 15:42:48 -0700 Date: Wed, 5 Jun 2019 15:45:53 -0700 From: Jacob Pan To: Auger Eric Cc: Alex Williamson , eric.auger.pro@gmail.com, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, joro@8bytes.org, yi.l.liu@intel.com, jean-philippe.brucker@arm.com, will.deacon@arm.com, robin.murphy@arm.com, kevin.tian@intel.com, ashok.raj@intel.com, marc.zyngier@arm.com, peter.maydell@linaro.org, vincent.stehle@arm.com, jacob.jun.pan@linux.intel.com Subject: Re: [PATCH v8 26/29] vfio-pci: Register an iommu fault handler Message-ID: <20190605154553.0d00ad8d@jacob-builder> In-Reply-To: <10dd60d9-4af0-c0eb-08c9-a0db7ee1925e@redhat.com> References: <20190526161004.25232-1-eric.auger@redhat.com> <20190526161004.25232-27-eric.auger@redhat.com> <20190603163139.70fe8839@x1.home> <10dd60d9-4af0-c0eb-08c9-a0db7ee1925e@redhat.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: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, 4 Jun 2019 18:11:08 +0200 Auger Eric wrote: > Hi Alex, > > On 6/4/19 12:31 AM, Alex Williamson wrote: > > On Sun, 26 May 2019 18:10:01 +0200 > > Eric Auger wrote: > > > >> This patch registers a fault handler which records faults in > >> a circular buffer and then signals an eventfd. This buffer is > >> exposed within the fault region. > >> > >> Signed-off-by: Eric Auger > >> > >> --- > >> > >> v3 -> v4: > >> - move iommu_unregister_device_fault_handler to vfio_pci_release > >> --- > >> drivers/vfio/pci/vfio_pci.c | 49 > >> +++++++++++++++++++++++++++++ drivers/vfio/pci/vfio_pci_private.h > >> | 1 + 2 files changed, 50 insertions(+) > >> > >> diff --git a/drivers/vfio/pci/vfio_pci.c > >> b/drivers/vfio/pci/vfio_pci.c index f75f61127277..520999994ba8 > >> 100644 --- a/drivers/vfio/pci/vfio_pci.c > >> +++ b/drivers/vfio/pci/vfio_pci.c > >> @@ -30,6 +30,7 @@ > >> #include > >> #include > >> #include > >> +#include > >> > >> #include "vfio_pci_private.h" > >> > >> @@ -296,6 +297,46 @@ static const struct vfio_pci_regops > >> vfio_pci_fault_prod_regops = { .add_capability = > >> vfio_pci_fault_prod_add_capability, }; > >> > >> +int vfio_pci_iommu_dev_fault_handler(struct iommu_fault_event > >> *evt, void *data) +{ > >> + struct vfio_pci_device *vdev = (struct vfio_pci_device *) > >> data; > >> + struct vfio_region_fault_prod *prod_region = > >> + (struct vfio_region_fault_prod > >> *)vdev->fault_pages; > >> + struct vfio_region_fault_cons *cons_region = > >> + (struct vfio_region_fault_cons > >> *)(vdev->fault_pages + 2 * PAGE_SIZE); > >> + struct iommu_fault *new = > >> + (struct iommu_fault *)(vdev->fault_pages + > >> prod_region->offset + > >> + prod_region->prod * > >> prod_region->entry_size); > >> + int prod, cons, size; > >> + > >> + mutex_lock(&vdev->fault_queue_lock); > >> + > >> + if (!vdev->fault_abi) > >> + goto unlock; > >> + > >> + prod = prod_region->prod; > >> + cons = cons_region->cons; > >> + size = prod_region->nb_entries; > >> + > >> + if (CIRC_SPACE(prod, cons, size) < 1) > >> + goto unlock; > >> + > >> + *new = evt->fault; > >> + prod = (prod + 1) % size; > >> + prod_region->prod = prod; > >> + mutex_unlock(&vdev->fault_queue_lock); > >> + > >> + mutex_lock(&vdev->igate); > >> + if (vdev->dma_fault_trigger) > >> + eventfd_signal(vdev->dma_fault_trigger, 1); > >> + mutex_unlock(&vdev->igate); > >> + return 0; > >> + > >> +unlock: > >> + mutex_unlock(&vdev->fault_queue_lock); > >> + return -EINVAL; > >> +} > >> + > >> static int vfio_pci_init_fault_region(struct vfio_pci_device > >> *vdev) { > >> struct vfio_region_fault_prod *header; > >> @@ -328,6 +369,13 @@ static int vfio_pci_init_fault_region(struct > >> vfio_pci_device *vdev) header = (struct vfio_region_fault_prod > >> *)vdev->fault_pages; header->version = -1; > >> header->offset = PAGE_SIZE; > >> + > >> + ret = > >> iommu_register_device_fault_handler(&vdev->pdev->dev, > >> + > >> vfio_pci_iommu_dev_fault_handler, > >> + vdev); > >> + if (ret) > >> + goto out; > >> + > >> return 0; > >> out: > >> kfree(vdev->fault_pages); > >> @@ -570,6 +618,7 @@ static void vfio_pci_release(void *device_data) > >> if (!(--vdev->refcnt)) { > >> vfio_spapr_pci_eeh_release(vdev->pdev); > >> vfio_pci_disable(vdev); > >> + > >> iommu_unregister_device_fault_handler(&vdev->pdev->dev); > > > > > > But this can fail if there are pending faults which leaves a device > > reference and then the system is broken :( > This series only features unrecoverable errors and for those the > unregistration cannot fail. Now unrecoverable errors were added I > admit this is confusing. We need to sort this out or clean the > dependencies. As Alex pointed out in 4/29, we can make iommu_unregister_device_fault_handler() never fail and clean up all the pending faults in the host IOMMU belong to that device. But the problem is that if a fault, such as PRQ, has already been injected into the guest, the page response may come back after handler is unregistered and registered again. We need a way to reject such page response belong to the previous life of the handler. Perhaps a sync call to the guest with your fault queue eventfd? I am not sure. Jacob