From:   Stefano Garzarella <sgarzare@redhat.com>
To:     virtualization@lists.linux-foundation.org
Cc:     Andrey Zhadchenko <andrey.zhadchenko@virtuozzo.com>,
        eperezma@redhat.com, netdev@vger.kernel.org, stefanha@redhat.com,
        linux-kernel@vger.kernel.org, Jason Wang <jasowang@redhat.com>,
        "Michael S. Tsirkin" <mst@redhat.com>, kvm@vger.kernel.org,
        Stefano Garzarella <sgarzare@redhat.com>
Subject: [PATCH v2 7/8] vdpa_sim: replace the spinlock with a mutex to protect the state
Date:   Thu,  2 Mar 2023 12:34:20 +0100
Message-Id: <20230302113421.174582-8-sgarzare@redhat.com>
In-Reply-To: <20230302113421.174582-1-sgarzare@redhat.com>
References: <20230302113421.174582-1-sgarzare@redhat.com>
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The spinlock we use to protect the state of the simulator is sometimes
held for a long time (for example, when devices handle requests).

This also prevents us from calling functions that might sleep (such as
kthread_flush_work() in the next patch), and thus having to release
and retake the lock.

For these reasons, let's replace the spinlock with a mutex that gives
us more flexibility.

Suggested-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
 drivers/vdpa/vdpa_sim/vdpa_sim.h     |  4 ++--
 drivers/vdpa/vdpa_sim/vdpa_sim.c     | 34 ++++++++++++++--------------
 drivers/vdpa/vdpa_sim/vdpa_sim_blk.c |  4 ++--
 drivers/vdpa/vdpa_sim/vdpa_sim_net.c |  4 ++--
 4 files changed, 23 insertions(+), 23 deletions(-)

diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.h b/drivers/vdpa/vdpa_sim/vdpa_sim.h
index ce83f9130a5d..4774292fba8c 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.h
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.h
@@ -60,8 +60,8 @@ struct vdpasim {
 	struct kthread_worker *worker;
 	struct kthread_work work;
 	struct vdpasim_dev_attr dev_attr;
-	/* spinlock to synchronize virtqueue state */
-	spinlock_t lock;
+	/* mutex to synchronize virtqueue state */
+	struct mutex mutex;
 	/* virtio config according to device type */
 	void *config;
 	struct vhost_iotlb *iommu;
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
index 6feb29726c2a..a28103a67ae7 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
@@ -166,7 +166,7 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
 	if (IS_ERR(vdpasim->worker))
 		goto err_iommu;
 
-	spin_lock_init(&vdpasim->lock);
+	mutex_init(&vdpasim->mutex);
 	spin_lock_init(&vdpasim->iommu_lock);
 
 	dev = &vdpasim->vdpa.dev;
@@ -275,13 +275,13 @@ static void vdpasim_set_vq_ready(struct vdpa_device *vdpa, u16 idx, bool ready)
 	struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
 	bool old_ready;
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	old_ready = vq->ready;
 	vq->ready = ready;
 	if (vq->ready && !old_ready) {
 		vdpasim_queue_ready(vdpasim, idx);
 	}
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 }
 
 static bool vdpasim_get_vq_ready(struct vdpa_device *vdpa, u16 idx)
@@ -299,9 +299,9 @@ static int vdpasim_set_vq_state(struct vdpa_device *vdpa, u16 idx,
 	struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
 	struct vringh *vrh = &vq->vring;
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	vrh->last_avail_idx = state->split.avail_index;
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	return 0;
 }
@@ -398,9 +398,9 @@ static u8 vdpasim_get_status(struct vdpa_device *vdpa)
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 	u8 status;
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	status = vdpasim->status;
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	return status;
 }
@@ -409,19 +409,19 @@ static void vdpasim_set_status(struct vdpa_device *vdpa, u8 status)
 {
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	vdpasim->status = status;
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 }
 
 static int vdpasim_reset(struct vdpa_device *vdpa)
 {
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	vdpasim->status = 0;
 	vdpasim_do_reset(vdpasim);
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	return 0;
 }
@@ -430,9 +430,9 @@ static int vdpasim_suspend(struct vdpa_device *vdpa)
 {
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	vdpasim->running = false;
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	return 0;
 }
@@ -442,7 +442,7 @@ static int vdpasim_resume(struct vdpa_device *vdpa)
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 	int i;
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 	vdpasim->running = true;
 
 	if (vdpasim->pending_kick) {
@@ -453,7 +453,7 @@ static int vdpasim_resume(struct vdpa_device *vdpa)
 		vdpasim->pending_kick = false;
 	}
 
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	return 0;
 }
@@ -525,14 +525,14 @@ static int vdpasim_set_group_asid(struct vdpa_device *vdpa, unsigned int group,
 
 	iommu = &vdpasim->iommu[asid];
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 
 	for (i = 0; i < vdpasim->dev_attr.nvqs; i++)
 		if (vdpasim_get_vq_group(vdpa, i) == group)
 			vringh_set_iotlb(&vdpasim->vqs[i].vring, iommu,
 					 &vdpasim->iommu_lock);
 
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	return 0;
 }
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
index eb4897c8541e..568119e1553f 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
@@ -290,7 +290,7 @@ static void vdpasim_blk_work(struct vdpasim *vdpasim)
 	bool reschedule = false;
 	int i;
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 
 	if (!(vdpasim->status & VIRTIO_CONFIG_S_DRIVER_OK))
 		goto out;
@@ -321,7 +321,7 @@ static void vdpasim_blk_work(struct vdpasim *vdpasim)
 		}
 	}
 out:
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	if (reschedule)
 		vdpasim_schedule_work(vdpasim);
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_net.c b/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
index e61a9ecbfafe..7ab434592bfe 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
@@ -201,7 +201,7 @@ static void vdpasim_net_work(struct vdpasim *vdpasim)
 	u64 rx_drops = 0, rx_overruns = 0, rx_errors = 0, tx_errors = 0;
 	int err;
 
-	spin_lock(&vdpasim->lock);
+	mutex_lock(&vdpasim->mutex);
 
 	if (!vdpasim->running)
 		goto out;
@@ -264,7 +264,7 @@ static void vdpasim_net_work(struct vdpasim *vdpasim)
 	}
 
 out:
-	spin_unlock(&vdpasim->lock);
+	mutex_unlock(&vdpasim->mutex);
 
 	u64_stats_update_begin(&net->tx_stats.syncp);
 	net->tx_stats.pkts += tx_pkts;
-- 
2.39.2