From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xu Zaibo Subject: Re: [PATCH v2 13/40] vfio: Add support for Shared Virtual Addressing Date: Sat, 1 Sep 2018 10:23:20 +0800 Message-ID: <5B89F818.7060300@huawei.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1d5b6529-4e5a-723c-3f1b-dd5a9adb490c-5wv7dgnIgG8@public.gmane.org> 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: Jean-Philippe Brucker , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-acpi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org Cc: xieyisheng1-hv44wF8Li93QT0dZR+AlfA@public.gmane.org, liubo95-hv44wF8Li93QT0dZR+AlfA@public.gmane.org, will.deacon-5wv7dgnIgG8@public.gmane.org, okaya-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org, liguozhu , fanghao11 , ashok.raj-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, rfranz-YGCgFSpz5w/QT0dZR+AlfA@public.gmane.org, kevin.tian-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, rgummal-gjFFaj9aHVfQT0dZR+AlfA@public.gmane.org, =?UTF-8?B?57Gz57Gz?= , dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, ilias.apalodimas-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, robin.murphy-5wv7dgnIgG8@public.gmane.org, christian.koenig-5C7GfCeVMHo@public.gmane.org List-Id: iommu@lists.linux-foundation.org Hi Jean, On 2018/8/31 21:34, Jean-Philippe Brucker wrote: > On 27/08/18 09:06, Xu Zaibo wrote: >>> +struct vfio_iommu_type1_bind_process { >>> + __u32 flags; >>> +#define VFIO_IOMMU_BIND_PID (1 << 0) >>> + __u32 pasid; >> As I am doing some works on the SVA patch set. I just consider why the >> user space need this pasid. >> Maybe, is it much more reasonable to set the pasid into all devices >> under the vfio container by >> a call back function from 'vfio_devices' while >> 'VFIO_IOMMU_BIND_PROCESS' CMD is executed >> in kernel land? I am not sure because there exists no suitable call back >> in 'vfio_device' at present. > When using vfio-pci, the kernel doesn't know how to program the PASID > into the device because the only kernel driver for the device is the > generic vfio-pci module. The PCI specification doesn't describe a way of > setting up the PASID, it's vendor-specific. Only the userspace > application owning the device (and calling VFIO_IOMMU_BIND) knows how to > do it, so we return the allocated PASID. > > Note that unlike vfio-mdev where applications share slices of a > function, with vfio-pci one application owns the whole function so it's > safe to let userspace set the PASID in hardware. With vfio-mdev it's the > kernel driver that should be in charge of setting the PASID as you > described, and we wouldn't have a reason to return the PASID in the > vfio_iommu_type1_bind_process structure. Understood. But I still get the following confusion: 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.) Maybe I misunderstood, hope you can help me clear it. Thank you very much. Thanks, Zaibo .