From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yang Zhang Subject: Re: [PATCH RFC] vhost: basic device IOTLB support Date: Mon, 4 Jan 2016 09:39:37 +0800 Message-ID: <5689CD59.6030900@gmail.com> References: <1451546025-15955-1-git-send-email-jasowang@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1451546025-15955-1-git-send-email-jasowang-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jason Wang , mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-api@vger.kernel.org On 2015/12/31 15:13, Jason Wang wrote: > This patch tries to implement an device IOTLB for vhost. This could be > used with for co-operation with userspace(qemu) implementation of > iommu for a secure DMA environment in guest. > > The idea is simple. When vhost meets an IOTLB miss, it will request > the assistance of userspace to do the translation, this is done > through: > > - Fill the translation request in a preset userspace address (This > address is set through ioctl VHOST_SET_IOTLB_REQUEST_ENTRY). > - Notify userspace through eventfd (This eventfd was set through ioctl > VHOST_SET_IOTLB_FD). > > When userspace finishes the translation, it will update the vhost > IOTLB through VHOST_UPDATE_IOTLB ioctl. Userspace is also in charge of > snooping the IOTLB invalidation of IOMMU IOTLB and use > VHOST_UPDATE_IOTLB to invalidate the possible entry in vhost. Is there any performance data shows the difference with IOTLB supporting? I doubt we may see performance decrease since the flush code path is longer than before. -- best regards yang