[RFC PATCH 0/9] vhost-nvme: new qemu nvme backend using nvme target

[Ming Lin]

On Tue, 2015-11-24 at 11:51 +0100, Paolo Bonzini wrote:
> 
> On 24/11/2015 08:27, Ming Lin wrote:
> > handle_notify (qemu/hw/block/dataplane/virtio-blk.c:126)
> > aio_dispatch (qemu/aio-posix.c:329)
> > aio_poll (qemu/aio-posix.c:474)
> > iothread_run (qemu/iothread.c:45)
> > start_thread (pthread_create.c:312)
> > /lib/x86_64-linux-gnu/libc.so.6(clone+0x6d)
> > 
> > I think I'll have a "nvme_dev_notify" similar as "handle_notify"
> > 
> > static void nvme_dev_notify(EventNotifier *e)
> > {
> >     ....
> > }
> > 
> > But then how can I know this notify is for cq or sq?
> 
> virtio-blk has a single queue, so it has a single EventNotifier.  Your
> code using multiple EventNotifiers is fine, you can use
> aio_set_event_notifier multiple times on the same iothread.

I feel below patch is close to right.
But I got "Co-routine re-entered recursively".

Program received signal SIGABRT, Aborted.
0x00007ffff4a45cc9 in __GI_raise (sig=sig at entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
56	../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory.
(gdb) bt
#0  0x00007ffff4a45cc9 in __GI_raise (sig=sig at entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
#1  0x00007ffff4a490d8 in __GI_abort () at abort.c:89
#2  0x0000555555b910d1 in qemu_coroutine_enter (co=0x5555577a9ce0, opaque=0x0) at /home/mlin/qemu/util/qemu-coroutine.c:111
#3  0x0000555555b282e0 in bdrv_co_io_em_complete (opaque=0x7fffd94e4a30, ret=0) at /home/mlin/qemu/block/io.c:2282
#4  0x0000555555ab8ba4 in thread_pool_completion_bh (opaque=0x555557d6d440) at /home/mlin/qemu/thread-pool.c:187
#5  0x0000555555ab7ab2 in aio_bh_call (bh=0x555557648110) at /home/mlin/qemu/async.c:64
#6  0x0000555555ab7b88 in aio_bh_poll (ctx=0x5555565b28f0) at /home/mlin/qemu/async.c:92
#7  0x0000555555acb3b6 in aio_dispatch (ctx=0x5555565b28f0) at /home/mlin/qemu/aio-posix.c:305
#8  0x0000555555ab8013 in aio_ctx_dispatch (source=0x5555565b28f0, callback=0x0, user_data=0x0) at /home/mlin/qemu/async.c:231
#9  0x00007ffff575ee04 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#10 0x0000555555ac8b35 in glib_pollfds_poll () at /home/mlin/qemu/main-loop.c:211
#11 0x0000555555ac8c36 in os_host_main_loop_wait (timeout=0) at /home/mlin/qemu/main-loop.c:256
#12 0x0000555555ac8cff in main_loop_wait (nonblocking=0) at /home/mlin/qemu/main-loop.c:504
#13 0x00005555558a41d4 in main_loop () at /home/mlin/qemu/vl.c:1920
#14 0x00005555558ac28a in main (argc=21, argv=0x7fffffffe4a8, envp=0x7fffffffe558) at /home/mlin/qemu/vl.c:4681
(gdb)

Would you help to take a look?

diff --git a/hw/block/nvme.c b/hw/block/nvme.c
index f27fd35..f542740 100644
--- a/hw/block/nvme.c
+++ b/hw/block/nvme.c
@@ -28,6 +28,8 @@
 #include "sysemu/sysemu.h"
 #include "qapi/visitor.h"
 #include "sysemu/block-backend.h"
+#include "sysemu/iothread.h"
+#include "qom/object_interfaces.h"
 
 #include "nvme.h"
 
@@ -549,7 +551,10 @@ static void nvme_cq_notifier(EventNotifier *e)
         container_of(e, NvmeCQueue, notifier);
 
     event_notifier_test_and_clear(&cq->notifier);
+
+    aio_context_acquire(cq->ctrl->ctx);
     nvme_post_cqes(cq);
+    aio_context_release(cq->ctrl->ctx);
 }
 
 static void nvme_init_cq_eventfd(NvmeCQueue *cq)
@@ -558,9 +563,12 @@ static void nvme_init_cq_eventfd(NvmeCQueue *cq)
     uint16_t offset = (cq->cqid*2+1) * (4 << NVME_CAP_DSTRD(n->bar.cap));
 
     event_notifier_init(&cq->notifier, 0);
-    event_notifier_set_handler(&cq->notifier, nvme_cq_notifier);
     memory_region_add_eventfd(&n->iomem,
         0x1000 + offset, 4, false, 0, &cq->notifier);
+    aio_context_acquire(n->ctx);
+    aio_set_event_notifier(n->ctx, &cq->notifier, false,
+                           nvme_cq_notifier);
+    aio_context_release(n->ctx);
 }
 
 static void nvme_sq_notifier(EventNotifier *e)
@@ -569,7 +577,9 @@ static void nvme_sq_notifier(EventNotifier *e)
         container_of(e, NvmeSQueue, notifier);
 
     event_notifier_test_and_clear(&sq->notifier);
+    aio_context_acquire(sq->ctrl->ctx);
     nvme_process_sq(sq);
+    aio_context_release(sq->ctrl->ctx);
 }
 
 static void nvme_init_sq_eventfd(NvmeSQueue *sq)
@@ -578,9 +588,22 @@ static void nvme_init_sq_eventfd(NvmeSQueue *sq)
     uint16_t offset = sq->sqid * 2 * (4 << NVME_CAP_DSTRD(n->bar.cap));
 
     event_notifier_init(&sq->notifier, 0);
-    event_notifier_set_handler(&sq->notifier, nvme_sq_notifier);
     memory_region_add_eventfd(&n->iomem,
         0x1000 + offset, 4, false, 0, &sq->notifier);
+    aio_context_acquire(n->ctx);
+    aio_set_event_notifier(n->ctx, &sq->notifier, false,
+                           nvme_sq_notifier);
+    aio_context_release(n->ctx);
+}
+
+static void nvme_init_iothread(NvmeCtrl *n)
+{
+    object_initialize(&n->internal_iothread_obj,
+                      sizeof(n->internal_iothread_obj),
+                      TYPE_IOTHREAD);
+    user_creatable_complete(OBJECT(&n->internal_iothread_obj), &error_abort);
+    n->iothread = &n->internal_iothread_obj;
+    n->ctx = iothread_get_aio_context(n->iothread);
 }
 
 static uint16_t nvme_set_db_memory(NvmeCtrl *n, const NvmeCmd *cmd)
@@ -595,6 +618,8 @@ static uint16_t nvme_set_db_memory(NvmeCtrl *n, const NvmeCmd *cmd)
         return NVME_INVALID_MEMORY_ADDRESS | NVME_DNR;
     }
 
+    nvme_init_iothread(n);
+
     /* This assumes all I/O queues are created before this command is handled.
      * We skip the admin queues. */
     for (i = 1; i < n->num_queues; i++) {
diff --git a/hw/block/nvme.h b/hw/block/nvme.h
index 608f202..b53e69d 100644
--- a/hw/block/nvme.h
+++ b/hw/block/nvme.h
@@ -727,6 +727,10 @@ typedef struct NvmeCtrl {
     NvmeSQueue      admin_sq;
     NvmeCQueue      admin_cq;
     NvmeIdCtrl      id_ctrl;
+
+    IOThread *iothread;
+    IOThread internal_iothread_obj;
+    AioContext *ctx;
 } NvmeCtrl;
 
 #endif /* HW_NVME_H */