From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jean-Philippe Brucker Subject: Re: [PATCH 08/37] iommu/fault: Handle mm faults Date: Thu, 15 Feb 2018 13:51:34 +0000 Message-ID: <800c2efe-10d7-5711-37d6-fb45df9b6e5c@arm.com> References: <20180212183352.22730-1-jean-philippe.brucker@arm.com> <20180212183352.22730-9-jean-philippe.brucker@arm.com> <20180214104621.7675579c@jacob-builder> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20180214104621.7675579c@jacob-builder> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Jacob Pan Cc: Mark Rutland , "ilias.apalodimas-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org" , "kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "xuzaibo-hv44wF8Li93QT0dZR+AlfA@public.gmane.org" , Will Deacon , "okaya-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org" , "ashok.raj-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org" , "bharatku-gjFFaj9aHVfQT0dZR+AlfA@public.gmane.org" , "linux-acpi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Catalin Marinas , "rfranz-YGCgFSpz5w/QT0dZR+AlfA@public.gmane.org" , "lenb-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org" , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org" , "bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , "dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org" , rjw@rjwyso List-Id: devicetree@vger.kernel.org On 14/02/18 18:46, Jacob Pan wrote: > On Mon, 12 Feb 2018 18:33:23 +0000 > Jean-Philippe Brucker wrote: [...] >> + if (!evt->pasid_valid) >> + return ret; > I guess for not we don't handle PRQ without PASID, right? No. I'm not sure how to implement it, though there have been some requests (see discussion on 1/37) >> + /* >> + * Special case: PASID Stop Marker (LRW = 0b100) doesn't >> expect a >> + * response. A Stop Marker may be generated when disabling a >> PASID >> + * (issuing a PASID stop request) in some PCI devices. >> + * >> + * When the mm_exit() callback returns from the device >> driver, no page >> + * request is generated for this PASID anymore and >> outstanding ones have >> + * been pushed to the IOMMU (as per PCIe 4.0r1.0 - 6.20.1 >> and 10.4.1.2 - >> + * Managing PASID TLP Prefix Usage). Some PCI devices will >> wait for all >> + * outstanding page requests to come back with a response >> before >> + * completing the PASID stop request. Others do not wait for >> page >> + * responses, and instead issue this Stop Marker that tells >> us when the >> + * PASID can be reallocated. >> + * >> + * We ignore the Stop Marker because: >> + * a. Page requests, which are posted requests, have been >> flushed to the >> + * IOMMU when mm_exit() returns, >> + * b. We flush all fault queues after mm_exit() returns and >> before >> + * freeing the PASID. >> + * >> + * So even though the Stop Marker might be issued by the >> device *after* >> + * the stop request completes, outstanding faults will have >> been dealt >> + * with by the time we free the PASID. >> + */ >> + if (evt->last_req && >> + !(evt->prot & (IOMMU_FAULT_READ | IOMMU_FAULT_WRITE))) >> + return IOMMU_PAGE_RESP_HANDLED; >> + > If we don't expect a page response, shouldn't it be filtered by the > IOMMU vendor driver in the first place? i.e. in the vendor IOMMU driver > PRQ handler, it will sanitize the request anyway, for anything that > does not need response, it will not call iommu_report_device_fault(). Right, we're not doing anything with the stop marker anyway. This encoding is also specific to PCI PRI, and maybe in future architectures, LRW = 0b100 will mean something else and will require a response. So filtering it in the IOMMU driver makes more sense. Thanks, Jean