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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 92BD8C43381 for ; Thu, 7 Mar 2019 11:43:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6A6532081B for ; Thu, 7 Mar 2019 11:43:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726487AbfCGLnY (ORCPT ); Thu, 7 Mar 2019 06:43:24 -0500 Received: from foss.arm.com ([217.140.101.70]:44196 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726150AbfCGLnY (ORCPT ); Thu, 7 Mar 2019 06:43:24 -0500 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 9CC521596; Thu, 7 Mar 2019 03:43:23 -0800 (PST) Received: from [10.1.197.2] (ostrya.cambridge.arm.com [10.1.197.2]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CB3E33F706; Thu, 7 Mar 2019 03:43:20 -0800 (PST) Subject: Re: [PATCH v4 03/22] iommu: introduce device fault report API To: Jacob Pan Cc: Eric Auger , "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" , "alex.williamson@redhat.com" , "yi.l.liu@linux.intel.com" , Will Deacon , Robin Murphy , Marc Zyngier , "peter.maydell@linaro.org" , "kevin.tian@intel.com" , "ashok.raj@intel.com" , Christoffer Dall References: <20190218135504.25048-1-eric.auger@redhat.com> <20190218135504.25048-4-eric.auger@redhat.com> <20190306154616.648e2523@jacob-builder> From: Jean-Philippe Brucker Message-ID: <1500594f-d7ea-94f2-01aa-0dc0e08b391b@arm.com> Date: Thu, 7 Mar 2019 11:42:59 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190306154616.648e2523@jacob-builder> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/03/2019 23:46, Jacob Pan wrote: > On Tue, 5 Mar 2019 15:03:41 +0000 > Jean-Philippe Brucker wrote: > >> On 18/02/2019 13:54, Eric Auger wrote: >> [...]> +/** >> > + * iommu_register_device_fault_handler() - Register a device fault >> > handler >> > + * @dev: the device >> > + * @handler: the fault handler >> > + * @data: private data passed as argument to the handler >> > + * >> > + * When an IOMMU fault event is received, call this handler with >> > the fault event >> > + * and data as argument. The handler should return 0 on success. >> > If the fault is >> > + * recoverable (IOMMU_FAULT_PAGE_REQ), the handler can also >> > complete >> > + * the fault by calling iommu_page_response() with one of the >> > following >> > + * response code: >> > + * - IOMMU_PAGE_RESP_SUCCESS: retry the translation >> > + * - IOMMU_PAGE_RESP_INVALID: terminate the fault >> > + * - IOMMU_PAGE_RESP_FAILURE: terminate the fault and stop >> > reporting >> > + *   page faults if possible.  >> >> The comment refers to function and values that haven't been defined >> yet. Either the page_response() patch should come before, or we need >> to split this patch. >> >> Something I missed before: if the handler fails (returns != 0) it >> should complete the fault by calling iommu_page_response(), if we're >> not doing it in iommu_report_device_fault(). It should be indicated >> in this comment. It's safe for the handler to call page_response() >> since we're not holding fault_param->lock when calling the handler. >> > If the page request fault is to be reported to a guest, the report > function cannot wait for the completion status. As long as the fault is > injected into the guest, the handler should complete with success. If > the PRQ report fails, IMHO, the caller of iommu_report_device_fault() > should send page_response, perhaps after clean up all partial response > of the group too. Ok, the caller (IOMMU driver) sending the page_response if iommu_report_device_fault() fails does make more sense. Agreed on the partial cleanup as well, we don't keep track of them here, but I need to add that to the io-pgfault layer. However some cleanup should probably happen in here... >> > +   /* we only report device fault if there is a handler >> > registered */ >> > +   mutex_lock(&dev->iommu_param->lock); >> > +   if (!dev->iommu_param->fault_param || >> > +           !dev->iommu_param->fault_param->handler) { >> > +           ret = -EINVAL; >> > +           goto done_unlock; >> > +   } >> > +   fparam = dev->iommu_param->fault_param; >> > +   if (evt->fault.type == IOMMU_FAULT_PAGE_REQ && >> > +       evt->fault.prm.flags & >> > IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE) { >> > +           evt_pending = kmemdup(evt, sizeof(struct >> > iommu_fault_event), >> > +                           GFP_KERNEL); >> > +           if (!evt_pending) { >> > +                   ret = -ENOMEM; >> > +                   goto done_unlock; >> > +           } >> > +           mutex_lock(&fparam->lock); >> > +           list_add_tail(&evt_pending->list, &fparam->faults); >> > +           mutex_unlock(&fparam->lock); >> > +   } >> > +   ret = fparam->handler(evt, fparam->data); ... if ret != 0, removing and freeing the pending event seems more appropriate here than asking our caller to do it Thanks, Jean >> > +done_unlock: >> > +   mutex_unlock(&dev->iommu_param->lock); >> > +   return ret; >> > +} >> > +EXPORT_SYMBOL_GPL(iommu_report_device_fault);  >> [...] > > [Jacob Pan]