Live update is a technique wherein an application saves its state, exec's
to an updated version of itself, and restores its state. Clients of the
application experience a brief suspension of service, on the order of
100's of milliseconds, but are otherwise unaffected.
Define and implement interfaces that allow vdpa devices to be preserved
across fork or exec, to support live update for applications such as qemu.
The device must be suspended during the update, but its dma mappings are
preserved, so the suspension is brief.
The VHOST_NEW_OWNER ioctl transfers device ownership and pinned memory
accounting from one process to another.
The VHOST_BACKEND_F_NEW_OWNER backend capability indicates that
VHOST_NEW_OWNER is supported.
The VHOST_IOTLB_REMAP message type updates a dma mapping with its userland
address in the new process.
The VHOST_BACKEND_F_IOTLB_REMAP backend capability indicates that
VHOST_IOTLB_REMAP is supported and required. Some devices do not
require it, because the userland address of each dma mapping is discarded
after being translated to a physical address.
Here is a pseudo-code sequence for performing live update, based on
suspend + reset because resume is not yet available. The vdpa device
descriptor, fd, remains open across the exec.
ioctl(fd, VHOST_VDPA_SUSPEND)
ioctl(fd, VHOST_VDPA_SET_STATUS, 0)
exec
ioctl(fd, VHOST_NEW_OWNER)
issue ioctls to re-create vrings
if VHOST_BACKEND_F_IOTLB_REMAP
foreach dma mapping
write(fd, {VHOST_IOTLB_REMAP, new_addr})
ioctl(fd, VHOST_VDPA_SET_STATUS,
ACKNOWLEDGE | DRIVER | FEATURES_OK | DRIVER_OK)
Steve Sistare (13):
vhost-vdpa: count pinned memory
vhost-vdpa: pass mm to bind
vhost-vdpa: VHOST_NEW_OWNER
vhost-vdpa: VHOST_BACKEND_F_NEW_OWNER
vhost-vdpa: VHOST_IOTLB_REMAP
vhost-vdpa: VHOST_BACKEND_F_IOTLB_REMAP
vhost-vdpa: flush workers on suspend
vduse: flush workers on suspend
vdpa_sim: reset must not run
vdpa_sim: flush workers on suspend
vdpa/mlx5: new owner capability
vdpa_sim: new owner capability
vduse: new owner capability
drivers/vdpa/mlx5/net/mlx5_vnet.c | 3 +-
drivers/vdpa/vdpa_sim/vdpa_sim.c | 24 ++++++-
drivers/vdpa/vdpa_user/vduse_dev.c | 32 +++++++++
drivers/vhost/vdpa.c | 101 +++++++++++++++++++++++++++--
drivers/vhost/vhost.c | 15 +++++
drivers/vhost/vhost.h | 1 +
include/uapi/linux/vhost.h | 10 +++
include/uapi/linux/vhost_types.h | 15 ++++-
8 files changed, 191 insertions(+), 10 deletions(-)
--
2.39.3
