linux/drivers/vhost/Kconfig

92 lines
2.5 KiB

vhost_net: a kernel-level virtio server What it is: vhost net is a character device that can be used to reduce the number of system calls involved in virtio networking. Existing virtio net code is used in the guest without modification. There's similarity with vringfd, with some differences and reduced scope - uses eventfd for signalling - structures can be moved around in memory at any time (good for migration, bug work-arounds in userspace) - write logging is supported (good for migration) - support memory table and not just an offset (needed for kvm) common virtio related code has been put in a separate file vhost.c and can be made into a separate module if/when more backends appear. I used Rusty's lguest.c as the source for developing this part : this supplied me with witty comments I wouldn't be able to write myself. What it is not: vhost net is not a bus, and not a generic new system call. No assumptions are made on how guest performs hypercalls. Userspace hypervisors are supported as well as kvm. How it works: Basically, we connect virtio frontend (configured by userspace) to a backend. The backend could be a network device, or a tap device. Backend is also configured by userspace, including vlan/mac etc. Status: This works for me, and I haven't see any crashes. Compared to userspace, people reported improved latency (as I save up to 4 system calls per packet), as well as better bandwidth and CPU utilization. Features that I plan to look at in the future: - mergeable buffers - zero copy - scalability tuning: figure out the best threading model to use Note on RCU usage (this is also documented in vhost.h, near private_pointer which is the value protected by this variant of RCU): what is happening is that the rcu_dereference() is being used in a workqueue item. The role of rcu_read_lock() is taken on by the start of execution of the workqueue item, of rcu_read_unlock() by the end of execution of the workqueue item, and of synchronize_rcu() by flush_workqueue()/flush_work(). In the future we might need to apply some gcc attribute or sparse annotation to the function passed to INIT_WORK(). Paul's ack below is for this RCU usage. (Includes fixes by Alan Cox <alan@linux.intel.com>, David L Stevens <dlstevens@us.ibm.com>, Chris Wright <chrisw@redhat.com>) Acked-by: Rusty Russell <rusty@rustcorp.com.au> Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2010-01-14 06:17:27 +00:00
vhost_net: a kernel-level virtio server What it is: vhost net is a character device that can be used to reduce the number of system calls involved in virtio networking. Existing virtio net code is used in the guest without modification. There's similarity with vringfd, with some differences and reduced scope - uses eventfd for signalling - structures can be moved around in memory at any time (good for migration, bug work-arounds in userspace) - write logging is supported (good for migration) - support memory table and not just an offset (needed for kvm) common virtio related code has been put in a separate file vhost.c and can be made into a separate module if/when more backends appear. I used Rusty's lguest.c as the source for developing this part : this supplied me with witty comments I wouldn't be able to write myself. What it is not: vhost net is not a bus, and not a generic new system call. No assumptions are made on how guest performs hypercalls. Userspace hypervisors are supported as well as kvm. How it works: Basically, we connect virtio frontend (configured by userspace) to a backend. The backend could be a network device, or a tap device. Backend is also configured by userspace, including vlan/mac etc. Status: This works for me, and I haven't see any crashes. Compared to userspace, people reported improved latency (as I save up to 4 system calls per packet), as well as better bandwidth and CPU utilization. Features that I plan to look at in the future: - mergeable buffers - zero copy - scalability tuning: figure out the best threading model to use Note on RCU usage (this is also documented in vhost.h, near private_pointer which is the value protected by this variant of RCU): what is happening is that the rcu_dereference() is being used in a workqueue item. The role of rcu_read_lock() is taken on by the start of execution of the workqueue item, of rcu_read_unlock() by the end of execution of the workqueue item, and of synchronize_rcu() by flush_workqueue()/flush_work(). In the future we might need to apply some gcc attribute or sparse annotation to the function passed to INIT_WORK(). Paul's ack below is for this RCU usage. (Includes fixes by Alan Cox <alan@linux.intel.com>, David L Stevens <dlstevens@us.ibm.com>, Chris Wright <chrisw@redhat.com>) Acked-by: Rusty Russell <rusty@rustcorp.com.au> Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2010-01-14 06:17:27 +00:00
vhost: introduce vDPA-based backend This patch introduces a vDPA-based vhost backend. This backend is built on top of the same interface defined in virtio-vDPA and provides a generic vhost interface for userspace to accelerate the virtio devices in guest. This backend is implemented as a vDPA device driver on top of the same ops used in virtio-vDPA. It will create char device entry named vhost-vdpa-$index for userspace to use. Userspace can use vhost ioctls on top of this char device to setup the backend. Vhost ioctls are extended to make it type agnostic and behave like a virtio device, this help to eliminate type specific API like what vhost_net/scsi/vsock did: - VHOST_VDPA_GET_DEVICE_ID: get the virtio device ID which is defined by virtio specification to differ from different type of devices - VHOST_VDPA_GET_VRING_NUM: get the maximum size of virtqueue supported by the vDPA device - VHSOT_VDPA_SET/GET_STATUS: set and get virtio status of vDPA device - VHOST_VDPA_SET/GET_CONFIG: access virtio config space - VHOST_VDPA_SET_VRING_ENABLE: enable a specific virtqueue For memory mapping, IOTLB API is mandated for vhost-vDPA which means userspace drivers are required to use VHOST_IOTLB_UPDATE/VHOST_IOTLB_INVALIDATE to add or remove mapping for a specific userspace memory region. The vhost-vDPA API is designed to be type agnostic, but it allows net device only in current stage. Due to the lacking of control virtqueue support, some features were filter out by vhost-vdpa. We will enable more features and devices in the near future. Signed-off-by: Tiwei Bie <tiwei.bie@intel.com> Signed-off-by: Eugenio Pérez <eperezma@redhat.com> Signed-off-by: Jason Wang <jasowang@redhat.com> Link: https://lore.kernel.org/r/20200326140125.19794-8-jasowang@redhat.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2020-03-26 22:01:23 +08:00
vhost: introduce vDPA-based backend This patch introduces a vDPA-based vhost backend. This backend is built on top of the same interface defined in virtio-vDPA and provides a generic vhost interface for userspace to accelerate the virtio devices in guest. This backend is implemented as a vDPA device driver on top of the same ops used in virtio-vDPA. It will create char device entry named vhost-vdpa-$index for userspace to use. Userspace can use vhost ioctls on top of this char device to setup the backend. Vhost ioctls are extended to make it type agnostic and behave like a virtio device, this help to eliminate type specific API like what vhost_net/scsi/vsock did: - VHOST_VDPA_GET_DEVICE_ID: get the virtio device ID which is defined by virtio specification to differ from different type of devices - VHOST_VDPA_GET_VRING_NUM: get the maximum size of virtqueue supported by the vDPA device - VHSOT_VDPA_SET/GET_STATUS: set and get virtio status of vDPA device - VHOST_VDPA_SET/GET_CONFIG: access virtio config space - VHOST_VDPA_SET_VRING_ENABLE: enable a specific virtqueue For memory mapping, IOTLB API is mandated for vhost-vDPA which means userspace drivers are required to use VHOST_IOTLB_UPDATE/VHOST_IOTLB_INVALIDATE to add or remove mapping for a specific userspace memory region. The vhost-vDPA API is designed to be type agnostic, but it allows net device only in current stage. Due to the lacking of control virtqueue support, some features were filter out by vhost-vdpa. We will enable more features and devices in the near future. Signed-off-by: Tiwei Bie <tiwei.bie@intel.com> Signed-off-by: Eugenio Pérez <eperezma@redhat.com> Signed-off-by: Jason Wang <jasowang@redhat.com> Link: https://lore.kernel.org/r/20200326140125.19794-8-jasowang@redhat.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2020-03-26 22:01:23 +08:00
vhost: introduce vDPA-based backend This patch introduces a vDPA-based vhost backend. This backend is built on top of the same interface defined in virtio-vDPA and provides a generic vhost interface for userspace to accelerate the virtio devices in guest. This backend is implemented as a vDPA device driver on top of the same ops used in virtio-vDPA. It will create char device entry named vhost-vdpa-$index for userspace to use. Userspace can use vhost ioctls on top of this char device to setup the backend. Vhost ioctls are extended to make it type agnostic and behave like a virtio device, this help to eliminate type specific API like what vhost_net/scsi/vsock did: - VHOST_VDPA_GET_DEVICE_ID: get the virtio device ID which is defined by virtio specification to differ from different type of devices - VHOST_VDPA_GET_VRING_NUM: get the maximum size of virtqueue supported by the vDPA device - VHSOT_VDPA_SET/GET_STATUS: set and get virtio status of vDPA device - VHOST_VDPA_SET/GET_CONFIG: access virtio config space - VHOST_VDPA_SET_VRING_ENABLE: enable a specific virtqueue For memory mapping, IOTLB API is mandated for vhost-vDPA which means userspace drivers are required to use VHOST_IOTLB_UPDATE/VHOST_IOTLB_INVALIDATE to add or remove mapping for a specific userspace memory region. The vhost-vDPA API is designed to be type agnostic, but it allows net device only in current stage. Due to the lacking of control virtqueue support, some features were filter out by vhost-vdpa. We will enable more features and devices in the near future. Signed-off-by: Tiwei Bie <tiwei.bie@intel.com> Signed-off-by: Eugenio Pérez <eperezma@redhat.com> Signed-off-by: Jason Wang <jasowang@redhat.com> Link: https://lore.kernel.org/r/20200326140125.19794-8-jasowang@redhat.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2020-03-26 22:01:23 +08:00