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Fri, 4 Jun 2021 10:03:08 +0800 Subject: Re: [RFC] /dev/ioasid uAPI proposal To: Jacob Pan References: <01fe5034-42c8-6923-32f1-e287cc36bccc@linux.intel.com> <20210601173323.GN1002214@nvidia.com> <23a482f9-b88a-da98-3800-f3fd9ea85fbd@huawei.com> <20210603111914.653c4f61@jacob-builder> From: Shenming Lu Message-ID: Date: Fri, 4 Jun 2021 10:03:08 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.2.2 MIME-Version: 1.0 In-Reply-To: <20210603111914.653c4f61@jacob-builder> Content-Language: en-US X-Originating-IP: [10.174.185.220] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpemm500022.china.huawei.com (7.185.36.162) X-CFilter-Loop: Reflected Cc: "kvm@vger.kernel.org" , Jason Wang , Kirti Wankhede , Jean-Philippe Brucker , "Jiang, Dave" , "Raj, Ashok" , Jonathan Corbet , Jason Gunthorpe , "wanghaibin.wang@huawei.com" , "Tian, Kevin" , "Alex Williamson \(alex.williamson@redhat.com\)" , David Gibson , David Woodhouse , LKML , "iommu@lists.linux-foundation.org" , Robin Murphy X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 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 Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On 2021/6/4 2:19, Jacob Pan wrote: > Hi Shenming, > > On Wed, 2 Jun 2021 12:50:26 +0800, Shenming Lu > wrote: > >> On 2021/6/2 1:33, Jason Gunthorpe wrote: >>> On Tue, Jun 01, 2021 at 08:30:35PM +0800, Lu Baolu wrote: >>> >>>> The drivers register per page table fault handlers to /dev/ioasid which >>>> will then register itself to iommu core to listen and route the per- >>>> device I/O page faults. >>> >>> I'm still confused why drivers need fault handlers at all? >> >> Essentially it is the userspace that needs the fault handlers, >> one case is to deliver the faults to the vIOMMU, and another >> case is to enable IOPF on the GPA address space for on-demand >> paging, it seems that both could be specified in/through the >> IOASID_ALLOC ioctl? >> > I would think IOASID_BIND_PGTABLE is where fault handler should be > registered. There wouldn't be any IO page fault without the binding anyway. Yeah, I also proposed this before, registering the handler in the BIND_PGTABLE ioctl does make sense for the guest page faults. :-) But how about the page faults from the GPA address space (it's page table is mapped through the MAP_DMA ioctl)? From your point of view, it seems that we should register the handler for the GPA address space in the (first) MAP_DMA ioctl. > > I also don't understand why device drivers should register the fault > handler, the fault is detected by the pIOMMU and injected to the vIOMMU. So > I think it should be the IOASID itself register the handler. Yeah, and it can also be said that the provider of the page table registers the handler (Baolu). Thanks, Shenming _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu