[Qemu-devel] [PULL 0/7] Block patches

[Qemu-devel] [PULL 0/7] Block patches

[Stefan Hajnoczi]

The following changes since commit 6cb4f6db4f4367faa33da85b15f75bbbd2bed2a6:

  Merge remote-tracking branch 'remotes/cleber/tags/python-next-pull-request' into staging (2019-03-07 16:16:02 +0000)

are available in the Git repository at:

  git://github.com/stefanha/qemu.git tags/block-pull-request

for you to fetch changes up to 6ca206204fa773c8626d59caf2a5676d6cc35f52:

  iothread: document about why we need explicit aio_poll() (2019-03-08 10:20:57 +0000)

----------------------------------------------------------------
Pull request

----------------------------------------------------------------

Anastasiia Rusakova (1):
  hw/block/virtio-blk: Clean req->dev repetitions

Peter Xu (5):
  iothread: replace init_done_cond with a semaphore
  iothread: create the gcontext unconditionally
  iothread: create main loop unconditionally
  iothread: push gcontext earlier in the thread_fn
  iothread: document about why we need explicit aio_poll()

Stefan Hajnoczi (1):
  MAINTAINERS: add missing support status fields

 MAINTAINERS               |  3 ++
 include/sysemu/iothread.h |  5 +--
 hw/block/virtio-blk.c     | 16 ++++---
 iothread.c                | 90 +++++++++++++++++++--------------------
 4 files changed, 57 insertions(+), 57 deletions(-)

-- 
2.20.1

[Qemu-devel] [PULL 1/7] MAINTAINERS: add missing support status fields

[Stefan Hajnoczi]

This patch adds the "S:" line for areas of the codebase that currently
lack a support status field.

Note that there are a few more areas that are more abstract and do not
correspond to a specific set of files.  They have not been modified.

Cc: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20190301163518.20702-1-stefanha@redhat.com
Message-Id: <20190301163518.20702-1-stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 MAINTAINERS | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 074ad46d47..1ed8cf7ee7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -338,6 +338,7 @@ F: include/hw/tricore/
 
 Multiarch Linux User Tests
 M: Alex Bennée <alex.bennee@linaro.org>
+S: Maintained
 F: tests/tcg/multiarch/
 
 Guest CPU Cores (KVM):
@@ -2094,6 +2095,7 @@ F: qemu.sasl
 Coroutines
 M: Stefan Hajnoczi <stefanha@redhat.com>
 M: Kevin Wolf <kwolf@redhat.com>
+S: Maintained
 F: util/*coroutine*
 F: include/qemu/coroutine*
 F: tests/test-coroutine.c
@@ -2540,6 +2542,7 @@ F: .gitlab-ci.yml
 Guest Test Compilation Support
 M: Alex Bennée <alex.bennee@linaro.org>
 R: Philippe Mathieu-Daudé <f4bug@amsat.org>
+S: Maintained
 F: tests/tcg/Makefile
 F: tests/tcg/Makefile.include
 L: qemu-devel@nongnu.org
-- 
2.20.1

[Qemu-devel] [PULL 2/7] hw/block/virtio-blk: Clean req->dev repetitions

[Stefan Hajnoczi]

From: Anastasiia Rusakova <arusakova917@gmail.com>

Some functions sometimes uses req->dev even though a local variable
VirtIOBlock* s = req->dev has already been defined.
Updated places to use s everywhere in the file.

Signed-off-by: Anastasiia Rusakova <arusakova917@gmail.com>
Message-id: 20190307161925.4158-1-rusakova.nastasia@icloud.com
Message-Id: <20190307161925.4158-1-rusakova.nastasia@icloud.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 hw/block/virtio-blk.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 0cc3c590b9..06e57a4d39 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -127,7 +127,7 @@ static void virtio_blk_rw_complete(void *opaque, int ret)
         }
 
         if (ret) {
-            int p = virtio_ldl_p(VIRTIO_DEVICE(req->dev), &req->out.type);
+            int p = virtio_ldl_p(VIRTIO_DEVICE(s), &req->out.type);
             bool is_read = !(p & VIRTIO_BLK_T_OUT);
             /* Note that memory may be dirtied on read failure.  If the
              * virtio request is not completed here, as is the case for
@@ -143,7 +143,7 @@ static void virtio_blk_rw_complete(void *opaque, int ret)
         }
 
         virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
-        block_acct_done(blk_get_stats(req->dev->blk), &req->acct);
+        block_acct_done(blk_get_stats(s->blk), &req->acct);
         virtio_blk_free_request(req);
     }
     aio_context_release(blk_get_aio_context(s->conf.conf.blk));
@@ -260,9 +260,9 @@ static int virtio_blk_handle_scsi_req(VirtIOBlockReq *req)
 {
     int status = VIRTIO_BLK_S_OK;
     struct virtio_scsi_inhdr *scsi = NULL;
-    VirtIODevice *vdev = VIRTIO_DEVICE(req->dev);
-    VirtQueueElement *elem = &req->elem;
     VirtIOBlock *blk = req->dev;
+    VirtIODevice *vdev = VIRTIO_DEVICE(blk);
+    VirtQueueElement *elem = &req->elem;
 
 #ifdef __linux__
     int i;
@@ -492,16 +492,18 @@ static void virtio_blk_submit_multireq(BlockBackend *blk, MultiReqBuffer *mrb)
 
 static void virtio_blk_handle_flush(VirtIOBlockReq *req, MultiReqBuffer *mrb)
 {
-    block_acct_start(blk_get_stats(req->dev->blk), &req->acct, 0,
+    VirtIOBlock *s = req->dev;
+
+    block_acct_start(blk_get_stats(s->blk), &req->acct, 0,
                      BLOCK_ACCT_FLUSH);
 
     /*
      * Make sure all outstanding writes are posted to the backing device.
      */
     if (mrb->is_write && mrb->num_reqs > 0) {
-        virtio_blk_submit_multireq(req->dev->blk, mrb);
+        virtio_blk_submit_multireq(s->blk, mrb);
     }
-    blk_aio_flush(req->dev->blk, virtio_blk_flush_complete, req);
+    blk_aio_flush(s->blk, virtio_blk_flush_complete, req);
 }
 
 static bool virtio_blk_sect_range_ok(VirtIOBlock *dev,
-- 
2.20.1

[Qemu-devel] [PULL 3/7] iothread: replace init_done_cond with a semaphore

[Stefan Hajnoczi]

From: Peter Xu <peterx@redhat.com>

Only sending an init-done message using lock+cond seems an overkill to
me.  Replacing it with a simpler semaphore.

Meanwhile, init the semaphore unconditionally, then we can destroy it
unconditionally too in finalize which seems cleaner.

Signed-off-by: Peter Xu <peterx@redhat.com>
Message-id: 20190306115532.23025-2-peterx@redhat.com
Message-Id: <20190306115532.23025-2-peterx@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 include/sysemu/iothread.h |  3 +--
 iothread.c                | 17 ++++-------------
 2 files changed, 5 insertions(+), 15 deletions(-)

diff --git a/include/sysemu/iothread.h b/include/sysemu/iothread.h
index 8a7ac2c528..50411ba54a 100644
--- a/include/sysemu/iothread.h
+++ b/include/sysemu/iothread.h
@@ -27,8 +27,7 @@ typedef struct {
     GMainContext *worker_context;
     GMainLoop *main_loop;
     GOnce once;
-    QemuMutex init_done_lock;
-    QemuCond init_done_cond;    /* is thread initialization done? */
+    QemuSemaphore init_done_sem; /* is thread init done? */
     bool stopping;              /* has iothread_stop() been called? */
     bool running;               /* should iothread_run() continue? */
     int thread_id;
diff --git a/iothread.c b/iothread.c
index e615b7ae52..6e297e9ef1 100644
--- a/iothread.c
+++ b/iothread.c
@@ -55,10 +55,8 @@ static void *iothread_run(void *opaque)
     rcu_register_thread();
 
     my_iothread = iothread;
-    qemu_mutex_lock(&iothread->init_done_lock);
     iothread->thread_id = qemu_get_thread_id();
-    qemu_cond_signal(&iothread->init_done_cond);
-    qemu_mutex_unlock(&iothread->init_done_lock);
+    qemu_sem_post(&iothread->init_done_sem);
 
     while (iothread->running) {
         aio_poll(iothread->ctx, true);
@@ -115,6 +113,7 @@ static void iothread_instance_init(Object *obj)
 
     iothread->poll_max_ns = IOTHREAD_POLL_MAX_NS_DEFAULT;
     iothread->thread_id = -1;
+    qemu_sem_init(&iothread->init_done_sem, 0);
 }
 
 static void iothread_instance_finalize(Object *obj)
@@ -123,10 +122,6 @@ static void iothread_instance_finalize(Object *obj)
 
     iothread_stop(iothread);
 
-    if (iothread->thread_id != -1) {
-        qemu_cond_destroy(&iothread->init_done_cond);
-        qemu_mutex_destroy(&iothread->init_done_lock);
-    }
     /*
      * Before glib2 2.33.10, there is a glib2 bug that GSource context
      * pointer may not be cleared even if the context has already been
@@ -145,6 +140,7 @@ static void iothread_instance_finalize(Object *obj)
         g_main_context_unref(iothread->worker_context);
         iothread->worker_context = NULL;
     }
+    qemu_sem_destroy(&iothread->init_done_sem);
 }
 
 static void iothread_complete(UserCreatable *obj, Error **errp)
@@ -173,8 +169,6 @@ static void iothread_complete(UserCreatable *obj, Error **errp)
         return;
     }
 
-    qemu_mutex_init(&iothread->init_done_lock);
-    qemu_cond_init(&iothread->init_done_cond);
     iothread->once = (GOnce) G_ONCE_INIT;
 
     /* This assumes we are called from a thread with useful CPU affinity for us
@@ -188,12 +182,9 @@ static void iothread_complete(UserCreatable *obj, Error **errp)
     g_free(name);
 
     /* Wait for initialization to complete */
-    qemu_mutex_lock(&iothread->init_done_lock);
     while (iothread->thread_id == -1) {
-        qemu_cond_wait(&iothread->init_done_cond,
-                       &iothread->init_done_lock);
+        qemu_sem_wait(&iothread->init_done_sem);
     }
-    qemu_mutex_unlock(&iothread->init_done_lock);
 }
 
 typedef struct {
-- 
2.20.1

[Qemu-devel] [PULL 4/7] iothread: create the gcontext unconditionally

[Stefan Hajnoczi]

From: Peter Xu <peterx@redhat.com>

In existing code we create the gcontext dynamically at the first
access of the gcontext from caller.  That can bring some complexity
and potential races during using iothread.  Since the context itself
is not that big a resource, and we won't have millions of iothread,
let's simply create the gcontext unconditionally.

This will also be a preparation work further to move the thread
context push operation earlier than before (now it's only pushed right
before we want to start running the gmainloop).

Removing the g_once since it's not necessary, while introducing a new
run_gcontext boolean to show whether we want to run the gcontext.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-id: 20190306115532.23025-3-peterx@redhat.com
Message-Id: <20190306115532.23025-3-peterx@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 include/sysemu/iothread.h |  2 +-
 iothread.c                | 43 +++++++++++++++++++--------------------
 2 files changed, 22 insertions(+), 23 deletions(-)

diff --git a/include/sysemu/iothread.h b/include/sysemu/iothread.h
index 50411ba54a..5f6240d5cb 100644
--- a/include/sysemu/iothread.h
+++ b/include/sysemu/iothread.h
@@ -24,9 +24,9 @@ typedef struct {
 
     QemuThread thread;
     AioContext *ctx;
+    bool run_gcontext;          /* whether we should run gcontext */
     GMainContext *worker_context;
     GMainLoop *main_loop;
-    GOnce once;
     QemuSemaphore init_done_sem; /* is thread init done? */
     bool stopping;              /* has iothread_stop() been called? */
     bool running;               /* should iothread_run() continue? */
diff --git a/iothread.c b/iothread.c
index 6e297e9ef1..6fa87876e0 100644
--- a/iothread.c
+++ b/iothread.c
@@ -65,7 +65,7 @@ static void *iothread_run(void *opaque)
          * We must check the running state again in case it was
          * changed in previous aio_poll()
          */
-        if (iothread->running && atomic_read(&iothread->worker_context)) {
+        if (iothread->running && atomic_read(&iothread->run_gcontext)) {
             GMainLoop *loop;
 
             g_main_context_push_thread_default(iothread->worker_context);
@@ -114,6 +114,8 @@ static void iothread_instance_init(Object *obj)
     iothread->poll_max_ns = IOTHREAD_POLL_MAX_NS_DEFAULT;
     iothread->thread_id = -1;
     qemu_sem_init(&iothread->init_done_sem, 0);
+    /* By default, we don't run gcontext */
+    atomic_set(&iothread->run_gcontext, 0);
 }
 
 static void iothread_instance_finalize(Object *obj)
@@ -143,6 +145,16 @@ static void iothread_instance_finalize(Object *obj)
     qemu_sem_destroy(&iothread->init_done_sem);
 }
 
+static void iothread_init_gcontext(IOThread *iothread)
+{
+    GSource *source;
+
+    iothread->worker_context = g_main_context_new();
+    source = aio_get_g_source(iothread_get_aio_context(iothread));
+    g_source_attach(source, iothread->worker_context);
+    g_source_unref(source);
+}
+
 static void iothread_complete(UserCreatable *obj, Error **errp)
 {
     Error *local_error = NULL;
@@ -157,6 +169,12 @@ static void iothread_complete(UserCreatable *obj, Error **errp)
         return;
     }
 
+    /*
+     * Init one GMainContext for the iothread unconditionally, even if
+     * it's not used
+     */
+    iothread_init_gcontext(iothread);
+
     aio_context_set_poll_params(iothread->ctx,
                                 iothread->poll_max_ns,
                                 iothread->poll_grow,
@@ -169,8 +187,6 @@ static void iothread_complete(UserCreatable *obj, Error **errp)
         return;
     }
 
-    iothread->once = (GOnce) G_ONCE_INIT;
-
     /* This assumes we are called from a thread with useful CPU affinity for us
      * to inherit.
      */
@@ -333,27 +349,10 @@ IOThreadInfoList *qmp_query_iothreads(Error **errp)
     return head;
 }
 
-static gpointer iothread_g_main_context_init(gpointer opaque)
-{
-    AioContext *ctx;
-    IOThread *iothread = opaque;
-    GSource *source;
-
-    iothread->worker_context = g_main_context_new();
-
-    ctx = iothread_get_aio_context(iothread);
-    source = aio_get_g_source(ctx);
-    g_source_attach(source, iothread->worker_context);
-    g_source_unref(source);
-
-    aio_notify(iothread->ctx);
-    return NULL;
-}
-
 GMainContext *iothread_get_g_main_context(IOThread *iothread)
 {
-    g_once(&iothread->once, iothread_g_main_context_init, iothread);
-
+    atomic_set(&iothread->run_gcontext, 1);
+    aio_notify(iothread->ctx);
     return iothread->worker_context;
 }
 
-- 
2.20.1

[Qemu-devel] [PULL 5/7] iothread: create main loop unconditionally

[Stefan Hajnoczi]

From: Peter Xu <peterx@redhat.com>

Since we've have the gcontext always there, create the main loop
altogether.  The iothread_run() is even cleaner.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-id: 20190306115532.23025-4-peterx@redhat.com
Message-Id: <20190306115532.23025-4-peterx@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 iothread.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/iothread.c b/iothread.c
index 6fa87876e0..9abdbace66 100644
--- a/iothread.c
+++ b/iothread.c
@@ -66,17 +66,8 @@ static void *iothread_run(void *opaque)
          * changed in previous aio_poll()
          */
         if (iothread->running && atomic_read(&iothread->run_gcontext)) {
-            GMainLoop *loop;
-
             g_main_context_push_thread_default(iothread->worker_context);
-            iothread->main_loop =
-                g_main_loop_new(iothread->worker_context, TRUE);
-            loop = iothread->main_loop;
-
             g_main_loop_run(iothread->main_loop);
-            iothread->main_loop = NULL;
-            g_main_loop_unref(loop);
-
             g_main_context_pop_thread_default(iothread->worker_context);
         }
     }
@@ -141,6 +132,8 @@ static void iothread_instance_finalize(Object *obj)
     if (iothread->worker_context) {
         g_main_context_unref(iothread->worker_context);
         iothread->worker_context = NULL;
+        g_main_loop_unref(iothread->main_loop);
+        iothread->main_loop = NULL;
     }
     qemu_sem_destroy(&iothread->init_done_sem);
 }
@@ -153,6 +146,7 @@ static void iothread_init_gcontext(IOThread *iothread)
     source = aio_get_g_source(iothread_get_aio_context(iothread));
     g_source_attach(source, iothread->worker_context);
     g_source_unref(source);
+    iothread->main_loop = g_main_loop_new(iothread->worker_context, TRUE);
 }
 
 static void iothread_complete(UserCreatable *obj, Error **errp)
-- 
2.20.1

[Qemu-devel] [PULL 6/7] iothread: push gcontext earlier in the thread_fn

[Stefan Hajnoczi]

From: Peter Xu <peterx@redhat.com>

We were pushing the context until right before running the gmainloop.
Now since we have everything unconditionally, we can move this
earlier.

One benefit is that now it's done even before init_done_sem, so as
long as the iothread user calls iothread_create() and completes, we
know that the thread stack is ready.

Signed-off-by: Peter Xu <peterx@redhat.com>
Message-id: 20190306115532.23025-5-peterx@redhat.com
Message-Id: <20190306115532.23025-5-peterx@redhat.com>

[Tweaked comment wording as discussed with Peter Xu.
--Stefan]

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 iothread.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/iothread.c b/iothread.c
index 9abdbace66..ad64c757ac 100644
--- a/iothread.c
+++ b/iothread.c
@@ -53,7 +53,11 @@ static void *iothread_run(void *opaque)
     IOThread *iothread = opaque;
 
     rcu_register_thread();
-
+    /*
+     * g_main_context_push_thread_default() must be called before anything
+     * in this new thread uses glib.
+     */
+    g_main_context_push_thread_default(iothread->worker_context);
     my_iothread = iothread;
     iothread->thread_id = qemu_get_thread_id();
     qemu_sem_post(&iothread->init_done_sem);
@@ -66,12 +70,11 @@ static void *iothread_run(void *opaque)
          * changed in previous aio_poll()
          */
         if (iothread->running && atomic_read(&iothread->run_gcontext)) {
-            g_main_context_push_thread_default(iothread->worker_context);
             g_main_loop_run(iothread->main_loop);
-            g_main_context_pop_thread_default(iothread->worker_context);
         }
     }
 
+    g_main_context_pop_thread_default(iothread->worker_context);
     rcu_unregister_thread();
     return NULL;
 }
-- 
2.20.1

[Qemu-devel] [PULL 7/7] iothread: document about why we need explicit aio_poll()

[Stefan Hajnoczi]

From: Peter Xu <peterx@redhat.com>

After consulting Paolo I know why we'd better keep the explicit
aio_poll() in iothread_run().  Document it directly into the code so
that future readers will know the answer from day one.

Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 20190306115532.23025-6-peterx@redhat.com
Message-Id: <20190306115532.23025-6-peterx@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 iothread.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/iothread.c b/iothread.c
index ad64c757ac..7130be58e3 100644
--- a/iothread.c
+++ b/iothread.c
@@ -63,6 +63,15 @@ static void *iothread_run(void *opaque)
     qemu_sem_post(&iothread->init_done_sem);
 
     while (iothread->running) {
+        /*
+         * Note: from functional-wise the g_main_loop_run() below can
+         * already cover the aio_poll() events, but we can't run the
+         * main loop unconditionally because explicit aio_poll() here
+         * is faster than g_main_loop_run() when we do not need the
+         * gcontext at all (e.g., pure block layer iothreads).  In
+         * other words, when we want to run the gcontext with the
+         * iothread we need to pay some performance for functionality.
+         */
         aio_poll(iothread->ctx, true);
 
         /*
-- 
2.20.1

Re: [Qemu-devel] [PULL 0/7] Block patches

[Peter Maydell]

On Fri, 8 Mar 2019 at 16:53, Stefan Hajnoczi <stefanha@redhat.com> wrote:
>
> The following changes since commit 6cb4f6db4f4367faa33da85b15f75bbbd2bed2a6:
>
>   Merge remote-tracking branch 'remotes/cleber/tags/python-next-pull-request' into staging (2019-03-07 16:16:02 +0000)
>
> are available in the Git repository at:
>
>   git://github.com/stefanha/qemu.git tags/block-pull-request
>
> for you to fetch changes up to 6ca206204fa773c8626d59caf2a5676d6cc35f52:
>
>   iothread: document about why we need explicit aio_poll() (2019-03-08 10:20:57 +0000)
>
> ----------------------------------------------------------------
> Pull request
>
> ----------------------------------------------------------------

Applied, thanks.

Please update the changelog at https://wiki.qemu.org/ChangeLog/4.0
for any user-visible changes.

-- PMM