mirror of https://github.com/xemu-project/xemu.git
virtio-blk: restart s->rq reqs in vq AioContexts
A virtio-blk device with the iothread-vq-mapping parameter has per-virtqueue AioContexts. It is not thread-safe to process s->rq requests in the BlockBackend AioContext since that may be different from the virtqueue's AioContext to which this request belongs. The code currently races and could crash. Adapt virtio_blk_dma_restart_cb() to first split s->rq into per-vq lists and then schedule a BH each vq's AioContext as necessary. This way requests are safely processed in their vq's AioContext. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Message-ID: <20240119135748.270944-5-stefanha@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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@ -1156,16 +1156,11 @@ static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
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static void virtio_blk_dma_restart_bh(void *opaque)
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{
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VirtIOBlock *s = opaque;
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VirtIOBlockReq *req = opaque;
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VirtIOBlock *s = req->dev; /* we're called with at least one request */
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VirtIOBlockReq *req;
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MultiReqBuffer mrb = {};
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WITH_QEMU_LOCK_GUARD(&s->rq_lock) {
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req = s->rq;
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s->rq = NULL;
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}
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while (req) {
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VirtIOBlockReq *next = req->next;
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if (virtio_blk_handle_request(req, &mrb)) {
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@ -1195,16 +1190,43 @@ static void virtio_blk_dma_restart_cb(void *opaque, bool running,
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RunState state)
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{
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VirtIOBlock *s = opaque;
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uint16_t num_queues = s->conf.num_queues;
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if (!running) {
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return;
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}
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/* Paired with dec in virtio_blk_dma_restart_bh() */
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blk_inc_in_flight(s->conf.conf.blk);
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/* Split the device-wide s->rq request list into per-vq request lists */
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g_autofree VirtIOBlockReq **vq_rq = g_new0(VirtIOBlockReq *, num_queues);
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VirtIOBlockReq *rq;
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aio_bh_schedule_oneshot(blk_get_aio_context(s->conf.conf.blk),
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virtio_blk_dma_restart_bh, s);
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WITH_QEMU_LOCK_GUARD(&s->rq_lock) {
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rq = s->rq;
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s->rq = NULL;
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}
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while (rq) {
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VirtIOBlockReq *next = rq->next;
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uint16_t idx = virtio_get_queue_index(rq->vq);
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rq->next = vq_rq[idx];
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vq_rq[idx] = rq;
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rq = next;
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}
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/* Schedule a BH to submit the requests in each vq's AioContext */
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for (uint16_t i = 0; i < num_queues; i++) {
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if (!vq_rq[i]) {
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continue;
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}
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/* Paired with dec in virtio_blk_dma_restart_bh() */
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blk_inc_in_flight(s->conf.conf.blk);
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aio_bh_schedule_oneshot(s->vq_aio_context[i],
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virtio_blk_dma_restart_bh,
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vq_rq[i]);
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}
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}
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static void virtio_blk_reset(VirtIODevice *vdev)
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