diff options
Diffstat (limited to 'hw/block/dataplane/virtio-blk.c')
| -rw-r--r-- | hw/block/dataplane/virtio-blk.c | 540 |
1 files changed, 540 insertions, 0 deletions
diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c new file mode 100644 index 0000000000..5baef2391a --- /dev/null +++ b/hw/block/dataplane/virtio-blk.c @@ -0,0 +1,540 @@ +/* + * Dedicated thread for virtio-blk I/O processing + * + * Copyright 2012 IBM, Corp. + * Copyright 2012 Red Hat, Inc. and/or its affiliates + * + * Authors: + * Stefan Hajnoczi <stefanha@redhat.com> + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + * + */ + +#include "trace.h" +#include "qemu/iov.h" +#include "qemu/thread.h" +#include "qemu/error-report.h" +#include "hw/virtio/dataplane/vring.h" +#include "ioq.h" +#include "migration/migration.h" +#include "block/block.h" +#include "hw/virtio/virtio-blk.h" +#include "virtio-blk.h" +#include "block/aio.h" + +enum { + SEG_MAX = 126, /* maximum number of I/O segments */ + VRING_MAX = SEG_MAX + 2, /* maximum number of vring descriptors */ + REQ_MAX = VRING_MAX, /* maximum number of requests in the vring, + * is VRING_MAX / 2 with traditional and + * VRING_MAX with indirect descriptors */ +}; + +typedef struct { + struct iocb iocb; /* Linux AIO control block */ + QEMUIOVector *inhdr; /* iovecs for virtio_blk_inhdr */ + unsigned int head; /* vring descriptor index */ + struct iovec *bounce_iov; /* used if guest buffers are unaligned */ + QEMUIOVector *read_qiov; /* for read completion /w bounce buffer */ +} VirtIOBlockRequest; + +struct VirtIOBlockDataPlane { + bool started; + bool stopping; + QEMUBH *start_bh; + QemuThread thread; + + VirtIOBlkConf *blk; + int fd; /* image file descriptor */ + + VirtIODevice *vdev; + Vring vring; /* virtqueue vring */ + EventNotifier *guest_notifier; /* irq */ + + /* Note that these EventNotifiers are assigned by value. This is + * fine as long as you do not call event_notifier_cleanup on them + * (because you don't own the file descriptor or handle; you just + * use it). + */ + AioContext *ctx; + EventNotifier io_notifier; /* Linux AIO completion */ + EventNotifier host_notifier; /* doorbell */ + + IOQueue ioqueue; /* Linux AIO queue (should really be per + dataplane thread) */ + VirtIOBlockRequest requests[REQ_MAX]; /* pool of requests, managed by the + queue */ + + unsigned int num_reqs; + + Error *migration_blocker; +}; + +/* Raise an interrupt to signal guest, if necessary */ +static void notify_guest(VirtIOBlockDataPlane *s) +{ + if (!vring_should_notify(s->vdev, &s->vring)) { + return; + } + + event_notifier_set(s->guest_notifier); +} + +static void complete_request(struct iocb *iocb, ssize_t ret, void *opaque) +{ + VirtIOBlockDataPlane *s = opaque; + VirtIOBlockRequest *req = container_of(iocb, VirtIOBlockRequest, iocb); + struct virtio_blk_inhdr hdr; + int len; + + if (likely(ret >= 0)) { + hdr.status = VIRTIO_BLK_S_OK; + len = ret; + } else { + hdr.status = VIRTIO_BLK_S_IOERR; + len = 0; + } + + trace_virtio_blk_data_plane_complete_request(s, req->head, ret); + + if (req->read_qiov) { + assert(req->bounce_iov); + qemu_iovec_from_buf(req->read_qiov, 0, req->bounce_iov->iov_base, len); + qemu_iovec_destroy(req->read_qiov); + g_slice_free(QEMUIOVector, req->read_qiov); + } + + if (req->bounce_iov) { + qemu_vfree(req->bounce_iov->iov_base); + g_slice_free(struct iovec, req->bounce_iov); + } + + qemu_iovec_from_buf(req->inhdr, 0, &hdr, sizeof(hdr)); + qemu_iovec_destroy(req->inhdr); + g_slice_free(QEMUIOVector, req->inhdr); + + /* According to the virtio specification len should be the number of bytes + * written to, but for virtio-blk it seems to be the number of bytes + * transferred plus the status bytes. + */ + vring_push(&s->vring, req->head, len + sizeof(hdr)); + + s->num_reqs--; +} + +static void complete_request_early(VirtIOBlockDataPlane *s, unsigned int head, + QEMUIOVector *inhdr, unsigned char status) +{ + struct virtio_blk_inhdr hdr = { + .status = status, + }; + + qemu_iovec_from_buf(inhdr, 0, &hdr, sizeof(hdr)); + qemu_iovec_destroy(inhdr); + g_slice_free(QEMUIOVector, inhdr); + + vring_push(&s->vring, head, sizeof(hdr)); + notify_guest(s); +} + +/* Get disk serial number */ +static void do_get_id_cmd(VirtIOBlockDataPlane *s, + struct iovec *iov, unsigned int iov_cnt, + unsigned int head, QEMUIOVector *inhdr) +{ + char id[VIRTIO_BLK_ID_BYTES]; + + /* Serial number not NUL-terminated when shorter than buffer */ + strncpy(id, s->blk->serial ? s->blk->serial : "", sizeof(id)); + iov_from_buf(iov, iov_cnt, 0, id, sizeof(id)); + complete_request_early(s, head, inhdr, VIRTIO_BLK_S_OK); +} + +static int do_rdwr_cmd(VirtIOBlockDataPlane *s, bool read, + struct iovec *iov, unsigned int iov_cnt, + long long offset, unsigned int head, + QEMUIOVector *inhdr) +{ + struct iocb *iocb; + QEMUIOVector qiov; + struct iovec *bounce_iov = NULL; + QEMUIOVector *read_qiov = NULL; + + qemu_iovec_init_external(&qiov, iov, iov_cnt); + if (!bdrv_qiov_is_aligned(s->blk->conf.bs, &qiov)) { + void *bounce_buffer = qemu_blockalign(s->blk->conf.bs, qiov.size); + + if (read) { + /* Need to copy back from bounce buffer on completion */ + read_qiov = g_slice_new(QEMUIOVector); + qemu_iovec_init(read_qiov, iov_cnt); + qemu_iovec_concat_iov(read_qiov, iov, iov_cnt, 0, qiov.size); + } else { + qemu_iovec_to_buf(&qiov, 0, bounce_buffer, qiov.size); + } + + /* Redirect I/O to aligned bounce buffer */ + bounce_iov = g_slice_new(struct iovec); + bounce_iov->iov_base = bounce_buffer; + bounce_iov->iov_len = qiov.size; + iov = bounce_iov; + iov_cnt = 1; + } + + iocb = ioq_rdwr(&s->ioqueue, read, iov, iov_cnt, offset); + + /* Fill in virtio block metadata needed for completion */ + VirtIOBlockRequest *req = container_of(iocb, VirtIOBlockRequest, iocb); + req->head = head; + req->inhdr = inhdr; + req->bounce_iov = bounce_iov; + req->read_qiov = read_qiov; + return 0; +} + +static int process_request(IOQueue *ioq, struct iovec iov[], + unsigned int out_num, unsigned int in_num, + unsigned int head) +{ + VirtIOBlockDataPlane *s = container_of(ioq, VirtIOBlockDataPlane, ioqueue); + struct iovec *in_iov = &iov[out_num]; + struct virtio_blk_outhdr outhdr; + QEMUIOVector *inhdr; + size_t in_size; + + /* Copy in outhdr */ + if (unlikely(iov_to_buf(iov, out_num, 0, &outhdr, + sizeof(outhdr)) != sizeof(outhdr))) { + error_report("virtio-blk request outhdr too short"); + return -EFAULT; + } + iov_discard_front(&iov, &out_num, sizeof(outhdr)); + + /* Grab inhdr for later */ + in_size = iov_size(in_iov, in_num); + if (in_size < sizeof(struct virtio_blk_inhdr)) { + error_report("virtio_blk request inhdr too short"); + return -EFAULT; + } + inhdr = g_slice_new(QEMUIOVector); + qemu_iovec_init(inhdr, 1); + qemu_iovec_concat_iov(inhdr, in_iov, in_num, + in_size - sizeof(struct virtio_blk_inhdr), + sizeof(struct virtio_blk_inhdr)); + iov_discard_back(in_iov, &in_num, sizeof(struct virtio_blk_inhdr)); + + /* TODO Linux sets the barrier bit even when not advertised! */ + outhdr.type &= ~VIRTIO_BLK_T_BARRIER; + + switch (outhdr.type) { + case VIRTIO_BLK_T_IN: + do_rdwr_cmd(s, true, in_iov, in_num, outhdr.sector * 512, head, inhdr); + return 0; + + case VIRTIO_BLK_T_OUT: + do_rdwr_cmd(s, false, iov, out_num, outhdr.sector * 512, head, inhdr); + return 0; + + case VIRTIO_BLK_T_SCSI_CMD: + /* TODO support SCSI commands */ + complete_request_early(s, head, inhdr, VIRTIO_BLK_S_UNSUPP); + return 0; + + case VIRTIO_BLK_T_FLUSH: + /* TODO fdsync not supported by Linux AIO, do it synchronously here! */ + if (qemu_fdatasync(s->fd) < 0) { + complete_request_early(s, head, inhdr, VIRTIO_BLK_S_IOERR); + } else { + complete_request_early(s, head, inhdr, VIRTIO_BLK_S_OK); + } + return 0; + + case VIRTIO_BLK_T_GET_ID: + do_get_id_cmd(s, in_iov, in_num, head, inhdr); + return 0; + + default: + error_report("virtio-blk unsupported request type %#x", outhdr.type); + qemu_iovec_destroy(inhdr); + g_slice_free(QEMUIOVector, inhdr); + return -EFAULT; + } +} + +static int flush_true(EventNotifier *e) +{ + return true; +} + +static void handle_notify(EventNotifier *e) +{ + VirtIOBlockDataPlane *s = container_of(e, VirtIOBlockDataPlane, + host_notifier); + + /* There is one array of iovecs into which all new requests are extracted + * from the vring. Requests are read from the vring and the translated + * descriptors are written to the iovecs array. The iovecs do not have to + * persist across handle_notify() calls because the kernel copies the + * iovecs on io_submit(). + * + * Handling io_submit() EAGAIN may require storing the requests across + * handle_notify() calls until the kernel has sufficient resources to + * accept more I/O. This is not implemented yet. + */ + struct iovec iovec[VRING_MAX]; + struct iovec *end = &iovec[VRING_MAX]; + struct iovec *iov = iovec; + + /* When a request is read from the vring, the index of the first descriptor + * (aka head) is returned so that the completed request can be pushed onto + * the vring later. + * + * The number of hypervisor read-only iovecs is out_num. The number of + * hypervisor write-only iovecs is in_num. + */ + int head; + unsigned int out_num = 0, in_num = 0; + unsigned int num_queued; + + event_notifier_test_and_clear(&s->host_notifier); + for (;;) { + /* Disable guest->host notifies to avoid unnecessary vmexits */ + vring_disable_notification(s->vdev, &s->vring); + + for (;;) { + head = vring_pop(s->vdev, &s->vring, iov, end, &out_num, &in_num); + if (head < 0) { + break; /* no more requests */ + } + + trace_virtio_blk_data_plane_process_request(s, out_num, in_num, + head); + + if (process_request(&s->ioqueue, iov, out_num, in_num, head) < 0) { + vring_set_broken(&s->vring); + break; + } + iov += out_num + in_num; + } + + if (likely(head == -EAGAIN)) { /* vring emptied */ + /* Re-enable guest->host notifies and stop processing the vring. + * But if the guest has snuck in more descriptors, keep processing. + */ + if (vring_enable_notification(s->vdev, &s->vring)) { + break; + } + } else { /* head == -ENOBUFS or fatal error, iovecs[] is depleted */ + /* Since there are no iovecs[] left, stop processing for now. Do + * not re-enable guest->host notifies since the I/O completion + * handler knows to check for more vring descriptors anyway. + */ + break; + } + } + + num_queued = ioq_num_queued(&s->ioqueue); + if (num_queued > 0) { + s->num_reqs += num_queued; + + int rc = ioq_submit(&s->ioqueue); + if (unlikely(rc < 0)) { + fprintf(stderr, "ioq_submit failed %d\n", rc); + exit(1); + } + } +} + +static int flush_io(EventNotifier *e) +{ + VirtIOBlockDataPlane *s = container_of(e, VirtIOBlockDataPlane, + io_notifier); + + return s->num_reqs > 0; +} + +static void handle_io(EventNotifier *e) +{ + VirtIOBlockDataPlane *s = container_of(e, VirtIOBlockDataPlane, + io_notifier); + + event_notifier_test_and_clear(&s->io_notifier); + if (ioq_run_completion(&s->ioqueue, complete_request, s) > 0) { + notify_guest(s); + } + + /* If there were more requests than iovecs, the vring will not be empty yet + * so check again. There should now be enough resources to process more + * requests. + */ + if (unlikely(vring_more_avail(&s->vring))) { + handle_notify(&s->host_notifier); + } +} + +static void *data_plane_thread(void *opaque) +{ + VirtIOBlockDataPlane *s = opaque; + + do { + aio_poll(s->ctx, true); + } while (!s->stopping || s->num_reqs > 0); + return NULL; +} + +static void start_data_plane_bh(void *opaque) +{ + VirtIOBlockDataPlane *s = opaque; + + qemu_bh_delete(s->start_bh); + s->start_bh = NULL; + qemu_thread_create(&s->thread, data_plane_thread, + s, QEMU_THREAD_JOINABLE); +} + +bool virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk, + VirtIOBlockDataPlane **dataplane) +{ + VirtIOBlockDataPlane *s; + int fd; + + *dataplane = NULL; + + if (!blk->data_plane) { + return true; + } + + if (blk->scsi) { + error_report("device is incompatible with x-data-plane, use scsi=off"); + return false; + } + + if (blk->config_wce) { + error_report("device is incompatible with x-data-plane, " + "use config-wce=off"); + return false; + } + + fd = raw_get_aio_fd(blk->conf.bs); + if (fd < 0) { + error_report("drive is incompatible with x-data-plane, " + "use format=raw,cache=none,aio=native"); + return false; + } + + s = g_new0(VirtIOBlockDataPlane, 1); + s->vdev = vdev; + s->fd = fd; + s->blk = blk; + + /* Prevent block operations that conflict with data plane thread */ + bdrv_set_in_use(blk->conf.bs, 1); + + error_setg(&s->migration_blocker, + "x-data-plane does not support migration"); + migrate_add_blocker(s->migration_blocker); + + *dataplane = s; + return true; +} + +void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s) +{ + if (!s) { + return; + } + + virtio_blk_data_plane_stop(s); + migrate_del_blocker(s->migration_blocker); + error_free(s->migration_blocker); + bdrv_set_in_use(s->blk->conf.bs, 0); + g_free(s); +} + +void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s) +{ + VirtQueue *vq; + int i; + + if (s->started) { + return; + } + + vq = virtio_get_queue(s->vdev, 0); + if (!vring_setup(&s->vring, s->vdev, 0)) { + return; + } + + s->ctx = aio_context_new(); + + /* Set up guest notifier (irq) */ + if (s->vdev->binding->set_guest_notifiers(s->vdev->binding_opaque, 1, + true) != 0) { + fprintf(stderr, "virtio-blk failed to set guest notifier, " + "ensure -enable-kvm is set\n"); + exit(1); + } + s->guest_notifier = virtio_queue_get_guest_notifier(vq); + + /* Set up virtqueue notify */ + if (s->vdev->binding->set_host_notifier(s->vdev->binding_opaque, + 0, true) != 0) { + fprintf(stderr, "virtio-blk failed to set host notifier\n"); + exit(1); + } + s->host_notifier = *virtio_queue_get_host_notifier(vq); + aio_set_event_notifier(s->ctx, &s->host_notifier, handle_notify, flush_true); + + /* Set up ioqueue */ + ioq_init(&s->ioqueue, s->fd, REQ_MAX); + for (i = 0; i < ARRAY_SIZE(s->requests); i++) { + ioq_put_iocb(&s->ioqueue, &s->requests[i].iocb); + } + s->io_notifier = *ioq_get_notifier(&s->ioqueue); + aio_set_event_notifier(s->ctx, &s->io_notifier, handle_io, flush_io); + + s->started = true; + trace_virtio_blk_data_plane_start(s); + + /* Kick right away to begin processing requests already in vring */ + event_notifier_set(virtio_queue_get_host_notifier(vq)); + + /* Spawn thread in BH so it inherits iothread cpusets */ + s->start_bh = qemu_bh_new(start_data_plane_bh, s); + qemu_bh_schedule(s->start_bh); +} + +void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s) +{ + if (!s->started || s->stopping) { + return; + } + s->stopping = true; + trace_virtio_blk_data_plane_stop(s); + + /* Stop thread or cancel pending thread creation BH */ + if (s->start_bh) { + qemu_bh_delete(s->start_bh); + s->start_bh = NULL; + } else { + aio_notify(s->ctx); + qemu_thread_join(&s->thread); + } + + aio_set_event_notifier(s->ctx, &s->io_notifier, NULL, NULL); + ioq_cleanup(&s->ioqueue); + + aio_set_event_notifier(s->ctx, &s->host_notifier, NULL, NULL); + s->vdev->binding->set_host_notifier(s->vdev->binding_opaque, 0, false); + + aio_context_unref(s->ctx); + + /* Clean up guest notifier (irq) */ + s->vdev->binding->set_guest_notifiers(s->vdev->binding_opaque, 1, false); + + vring_teardown(&s->vring); + s->started = false; + s->stopping = false; +} |