Hi all, v1->v2: - Corrected typos and clarifications from first review - Added SHMEM_CONFIG frontend request to query VIRTIO shared memory regions from backends - vhost-user-device to use SHMEM_CONFIG to request and initialise regions - Added MEM_READ/WRITE backend requests in case address translation fails accessing VIRTIO Shared Memory Regions with MMAPs
This is an update of my attempt to have backends support dynamic fd mapping into VIRTIO Shared Memory Regions. After the first review I have added more commits and new messages to the vhost-user protocol. However, I still have some doubts as to how will this work, specially regarding the MEM_READ and MEM_WRITE commands. Thus, I am still looking for feedback, to ensure that I am going in the right direction with the implementation. The usecase for this patch is, e.g., to support vhost-user-gpu RESOURCE_BLOB operations, or DAX Window request for virtio-fs. In general, any operation where a backend need to request the frontend to mmap an fd into a VIRTIO Shared Memory Region, so that the guest can then access it. After receiving the SHMEM_MAP/UNMAP request, the frontend will perform the mmap with the instructed parameters (i.e., shmid, shm_offset, fd_offset, fd, lenght). As there are already a couple devices that could benefit of such a feature, and more could require it in the future, the goal is to make the implementation generic. To that end, the VIRTIO Shared Memory Region list is declared in the `VirtIODevice` struct. This patch also includes: SHMEM_CONFIG frontend request that is specifically meant to allow generic vhost-user-device frontend to be able to query VIRTIO Shared Memory settings from the backend (as this device is generic and agnostic of the actual backend configuration). Finally, MEM_READ/WRITE backend requests are added to deal with a potential issue when having any backend sharing a descriptor that references a mapping to another backend. The first backend will not be able to see these mappings. So these requests are a fallback for vhost-user memory translation fails. Albert Esteve (5): vhost-user: Add VIRTIO Shared Memory map request vhost_user: Add frontend command for shmem config vhost-user-dev: Add cache BAR vhost_user: Add MEM_READ/WRITE backend requests vhost_user: Implement mem_read/mem_write handlers docs/interop/vhost-user.rst | 58 ++++++ hw/virtio/vhost-user-base.c | 39 +++- hw/virtio/vhost-user-device-pci.c | 37 +++- hw/virtio/vhost-user.c | 221 ++++++++++++++++++++++ hw/virtio/virtio.c | 12 ++ include/hw/virtio/vhost-backend.h | 6 + include/hw/virtio/vhost-user.h | 1 + include/hw/virtio/virtio.h | 5 + subprojects/libvhost-user/libvhost-user.c | 149 +++++++++++++++ subprojects/libvhost-user/libvhost-user.h | 91 +++++++++ 10 files changed, 614 insertions(+), 5 deletions(-) -- 2.45.2
