A virtio-fs device's VM state consists of: - the virtio device (vring) state (VMSTATE_VIRTIO_DEVICE) - the back-end's (virtiofsd's) internal state
We get/set the latter via the new vhost-user operations FS_SET_STATE_FD, FS_GET_STATE, and FS_SET_STATE. Signed-off-by: Hanna Czenczek <hre...@redhat.com> --- hw/virtio/vhost-user-fs.c | 171 +++++++++++++++++++++++++++++++++++++- 1 file changed, 170 insertions(+), 1 deletion(-) diff --git a/hw/virtio/vhost-user-fs.c b/hw/virtio/vhost-user-fs.c index 83fc20e49e..df1fb02acc 100644 --- a/hw/virtio/vhost-user-fs.c +++ b/hw/virtio/vhost-user-fs.c @@ -20,8 +20,10 @@ #include "hw/virtio/virtio-bus.h" #include "hw/virtio/virtio-access.h" #include "qemu/error-report.h" +#include "qemu/memfd.h" #include "hw/virtio/vhost.h" #include "hw/virtio/vhost-user-fs.h" +#include "migration/qemu-file-types.h" #include "monitor/monitor.h" #include "sysemu/sysemu.h" @@ -298,9 +300,176 @@ static struct vhost_dev *vuf_get_vhost(VirtIODevice *vdev) return &fs->vhost_dev; } +/** + * Fetch the internal state from the back-end (virtiofsd) and save it + * to `f`. + */ +static int vuf_save_state(QEMUFile *f, void *pv, size_t size, + const VMStateField *field, JSONWriter *vmdesc) +{ + VirtIODevice *vdev = pv; + VHostUserFS *fs = VHOST_USER_FS(vdev); + int memfd = -1; + /* Size of the shared memory through which to transfer the state */ + const size_t chunk_size = 4 * 1024 * 1024; + size_t state_offset; + ssize_t remaining; + void *shm_buf; + Error *local_err = NULL; + int ret, ret2; + + /* Set up shared memory through which to receive the state from virtiofsd */ + shm_buf = qemu_memfd_alloc("vhost-fs-state", chunk_size, + F_SEAL_SEAL | F_SEAL_SHRINK | F_SEAL_GROW, + &memfd, &local_err); + if (!shm_buf) { + error_report_err(local_err); + ret = -ENOMEM; + goto early_fail; + } + + /* Share the SHM area with virtiofsd */ + ret = vhost_fs_set_state_fd(&fs->vhost_dev, memfd, chunk_size); + if (ret < 0) { + goto early_fail; + } + + /* Receive the virtiofsd state in chunks, and write them to `f` */ + state_offset = 0; + do { + size_t this_chunk_size; + + remaining = vhost_fs_get_state(&fs->vhost_dev, state_offset, + chunk_size); + if (remaining < 0) { + ret = remaining; + goto fail; + } + + /* Prefix the whole state by its total length */ + if (state_offset == 0) { + qemu_put_be64(f, remaining); + } + + this_chunk_size = MIN(remaining, chunk_size); + qemu_put_buffer(f, shm_buf, this_chunk_size); + state_offset += this_chunk_size; + } while (remaining >= chunk_size); + + ret = 0; +fail: + /* Have virtiofsd close the shared memory */ + ret2 = vhost_fs_set_state_fd(&fs->vhost_dev, -1, 0); + if (ret2 < 0) { + error_report("Failed to remove state FD from the vhost-user-fs back " + "end: %s", strerror(-ret)); + if (ret == 0) { + ret = ret2; + } + } + +early_fail: + if (shm_buf) { + qemu_memfd_free(shm_buf, chunk_size, memfd); + } + + return ret; +} + +/** + * Load the back-end's (virtiofsd's) internal state from `f` and send + * it over to that back-end. + */ +static int vuf_load_state(QEMUFile *f, void *pv, size_t size, + const VMStateField *field) +{ + VirtIODevice *vdev = pv; + VHostUserFS *fs = VHOST_USER_FS(vdev); + int memfd = -1; + /* Size of the shared memory through which to transfer the state */ + const size_t chunk_size = 4 * 1024 * 1024; + size_t state_offset; + uint64_t remaining; + void *shm_buf; + Error *local_err = NULL; + int ret, ret2; + + /* The state is prefixed by its total length, read that first */ + remaining = qemu_get_be64(f); + + /* Set up shared memory through which to send the state to virtiofsd */ + shm_buf = qemu_memfd_alloc("vhost-fs-state", chunk_size, + F_SEAL_SEAL | F_SEAL_SHRINK | F_SEAL_GROW, + &memfd, &local_err); + if (!shm_buf) { + error_report_err(local_err); + ret = -ENOMEM; + goto early_fail; + } + + /* Share the SHM area with virtiofsd */ + ret = vhost_fs_set_state_fd(&fs->vhost_dev, memfd, chunk_size); + if (ret < 0) { + goto early_fail; + } + + /* + * Read the virtiofsd state in chunks from `f`, and send them over + * to virtiofsd + */ + state_offset = 0; + do { + size_t this_chunk_size = MIN(remaining, chunk_size); + + if (qemu_get_buffer(f, shm_buf, this_chunk_size) < this_chunk_size) { + ret = -EINVAL; + goto fail; + } + + ret = vhost_fs_set_state(&fs->vhost_dev, state_offset, this_chunk_size); + if (ret < 0) { + goto fail; + } + + state_offset += this_chunk_size; + remaining -= this_chunk_size; + } while (remaining > 0); + + ret = 0; +fail: + ret2 = vhost_fs_set_state_fd(&fs->vhost_dev, -1, 0); + if (ret2 < 0) { + error_report("Failed to remove state FD from the vhost-user-fs back " + "end -- perhaps it failed to deserialize/apply the state: " + "%s", strerror(-ret2)); + if (ret == 0) { + ret = ret2; + } + } + +early_fail: + if (shm_buf) { + qemu_memfd_free(shm_buf, chunk_size, memfd); + } + + return ret; +} + static const VMStateDescription vuf_vmstate = { .name = "vhost-user-fs", - .unmigratable = 1, + .version_id = 1, + .fields = (VMStateField[]) { + VMSTATE_VIRTIO_DEVICE, + { + .name = "back-end", + .info = &(const VMStateInfo) { + .name = "virtio-fs back-end state", + .get = vuf_load_state, + .put = vuf_save_state, + }, + }, + VMSTATE_END_OF_LIST() + }, }; static Property vuf_properties[] = { -- 2.39.1