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, URIBL_BLOCKED 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 1F97CC28EB4 for ; Thu, 6 Jun 2019 18:54:15 +0000 (UTC) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0781C2083D for ; Thu, 6 Jun 2019 18:54:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0781C2083D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id B9BDDD07; Thu, 6 Jun 2019 18:54:14 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id AC5559F0 for ; Thu, 6 Jun 2019 18:54:13 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from foss.arm.com (foss.arm.com [217.140.101.70]) by smtp1.linuxfoundation.org (Postfix) with ESMTP id 1EC53A8 for ; Thu, 6 Jun 2019 18:54:12 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A289EA78; Thu, 6 Jun 2019 11:54:12 -0700 (PDT) Received: from [10.37.10.101] (unknown [10.37.10.101]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DC8583F5AF; Thu, 6 Jun 2019 11:54:07 -0700 (PDT) Subject: Re: [PATCH v8 26/29] vfio-pci: Register an iommu fault handler To: Jacob Pan , Auger Eric 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> <20190605154553.0d00ad8d@jacob-builder> From: Jean-Philippe Brucker Message-ID: <2753d192-1c46-d78e-c425-0c828e48cde2@arm.com> Date: Thu, 6 Jun 2019 19:54:05 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190605154553.0d00ad8d@jacob-builder> Content-Language: en-US Cc: "peter.maydell@linaro.org" , "kevin.tian@intel.com" , "ashok.raj@intel.com" , "kvm@vger.kernel.org" , Marc Zyngier , Will Deacon , "linux-kernel@vger.kernel.org" , "iommu@lists.linux-foundation.org" , Alex Williamson , Vincent Stehle , Robin Murphy , "kvmarm@lists.cs.columbia.edu" , "eric.auger.pro@gmail.com" X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org On 05/06/2019 23:45, Jacob Pan wrote: > 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. I'm trying to figure out if that would be harmful in any way. I guess it can be a bit nasty if we handle the page response right after having injected a new page request that uses the same PRGI. In any other case we discard the page response, but here we forward it to the endpoint and: * If the response status is success, endpoint retries the translation. The guest probably hasn't had time to handle the new page request and translation will fail, which may lead the endpoint to give up (two unsuccessful translation requests). Or send a new request * otherwise the endpoint won't retry the access, and could also disable PRI if the status is failure. > 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. We could simply expect the device driver not to send any page response after unregistering the fault handler. Is there any reason VFIO would need to unregister and re-register the fault handler on a live guest? Thanks, Jean _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu