From mboxrd@z Thu Jan 1 00:00:00 1970 From: xuzaibo@huawei.com (Xu Zaibo) Date: Wed, 5 Sep 2018 11:15:37 +0800 Subject: [PATCH v2 13/40] vfio: Add support for Shared Virtual Addressing In-Reply-To: References: <20180511190641.23008-1-jean-philippe.brucker@arm.com> <20180511190641.23008-14-jean-philippe.brucker@arm.com> <5B83B11E.7010807@huawei.com> <1d5b6529-4e5a-723c-3f1b-dd5a9adb490c@arm.com> <5B89F818.7060300@huawei.com> <3a961aff-e830-64bb-b6a9-14e08de1abf5@arm.com> <5B8DEA15.7020404@huawei.com> Message-ID: <5B8F4A59.20004@huawei.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi, On 2018/9/4 18:57, Jean-Philippe Brucker wrote: > On 04/09/2018 03:12, Xu Zaibo wrote: >> On 2018/9/3 18:34, Jean-Philippe Brucker wrote: >>> On 01/09/18 03:23, Xu Zaibo wrote: >>>> As one application takes a whole function while using VFIO-PCI, why do >>>> the application and the >>>> function need to enable PASID capability? (Since just one I/O page table >>>> is enough for them.) >>> At the moment the series doesn't provide support for SVA without PASID >>> (on the I/O page fault path, 08/40). In addition the BIND ioctl could be >>> used by the owner application to bind other processes (slaves) and >>> perform sub-assignment. But that feature is incomplete because we don't >>> send stop_pasid notification to the owner when a slave dies. >>> >> So, Could I understand like this? >> >> 1. While the series are finished well, VFIO-PCI device can be held >> by only one process >> through binding IOCTL command without PASID (without PASID >> being exposed user space). > It could, but isn't supported at the moment. In addition to adding > support in the I/O page fault code, we'd also need to update the VFIO > API. Currently a VFIO_TYPE1 domain always supports the MAP/UNMAP ioctl. > The case you describe isn't compatible with MAP/UNMAP, since the process > manages the shared address space with mmap or malloc. We'd probably need > to introduce a new VFIO IOMMU type, in which case the bind could be > performed implicitly when the process does VFIO_SET_IOMMU. Then the > process wouldn't need to send an additional BIND IOCTL. ok. got it. This is the legacy mode, so all the VFIO APIs are kept unchanged? >> 2. While using VFIO-PCI device to support multiple processes with >> SVA series, a primary >> process with multiple secondary processes must be deployed just >> like DPDK(https://www.dpdk.org/). >> And, the PASID still has to be exposed to user land. > Right. A third case, also implemented by this patch (and complete), is > the primary process simply doing a BIND for itself, and using the > returned PASID to share its own address space with the device. > ok. But I am worried that the sulotion of one primary processes with several secondary ones is a little bit limited. Maybe, users don't want to depend on the primary process. :) Thanks, Zaibo .