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