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References: <20230302113421.174582-1-sgarzare@redhat.com> <20230302113421.174582-8-sgarzare@redhat.com>
In-Reply-To: <20230302113421.174582-8-sgarzare@redhat.com>
From:   Jason Wang <jasowang@redhat.com>
Date:   Tue, 14 Mar 2023 13:29:16 +0800
Message-ID: <CACGkMEuCUBQeg0gLUjBXff=zMf-=qJqhMpdeUvTDk55Gz6tAVA@mail.gmail.com>
Subject: Re: [PATCH v2 7/8] vdpa_sim: replace the spinlock with a mutex to
 protect the state
To:     Stefano Garzarella <sgarzare@redhat.com>
Cc:     virtualization@lists.linux-foundation.org,
        Andrey Zhadchenko <andrey.zhadchenko@virtuozzo.com>,
        eperezma@redhat.com, netdev@vger.kernel.org, stefanha@redhat.com,
        linux-kernel@vger.kernel.org,
        "Michael S. Tsirkin" <mst@redhat.com>, kvm@vger.kernel.org
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On Thu, Mar 2, 2023 at 7:35=E2=80=AFPM Stefano Garzarella <sgarzare@redhat.=
com> wrote:
>
> 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>

Acked-by: Jason Wang <jasowang@redhat.com>

Thanks

> ---
>  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/vdp=
a_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/vdp=
a_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_att=
r *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 =3D &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 =3D &vdpasim->vqs[idx];
>         bool old_ready;
>
> -       spin_lock(&vdpasim->lock);
> +       mutex_lock(&vdpasim->mutex);
>         old_ready =3D vq->ready;
>         vq->ready =3D 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 *v=
dpa, u16 idx,
>         struct vdpasim_virtqueue *vq =3D &vdpasim->vqs[idx];
>         struct vringh *vrh =3D &vq->vring;
>
> -       spin_lock(&vdpasim->lock);
> +       mutex_lock(&vdpasim->mutex);
>         vrh->last_avail_idx =3D 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 =3D vdpa_to_sim(vdpa);
>         u8 status;
>
> -       spin_lock(&vdpasim->lock);
> +       mutex_lock(&vdpasim->mutex);
>         status =3D 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 =3D vdpa_to_sim(vdpa);
>
> -       spin_lock(&vdpasim->lock);
> +       mutex_lock(&vdpasim->mutex);
>         vdpasim->status =3D status;
> -       spin_unlock(&vdpasim->lock);
> +       mutex_unlock(&vdpasim->mutex);
>  }
>
>  static int vdpasim_reset(struct vdpa_device *vdpa)
>  {
>         struct vdpasim *vdpasim =3D vdpa_to_sim(vdpa);
>
> -       spin_lock(&vdpasim->lock);
> +       mutex_lock(&vdpasim->mutex);
>         vdpasim->status =3D 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 =3D vdpa_to_sim(vdpa);
>
> -       spin_lock(&vdpasim->lock);
> +       mutex_lock(&vdpasim->mutex);
>         vdpasim->running =3D 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 =3D vdpa_to_sim(vdpa);
>         int i;
>
> -       spin_lock(&vdpasim->lock);
> +       mutex_lock(&vdpasim->mutex);
>         vdpasim->running =3D true;
>
>         if (vdpasim->pending_kick) {
> @@ -453,7 +453,7 @@ static int vdpasim_resume(struct vdpa_device *vdpa)
>                 vdpasim->pending_kick =3D false;
>         }
>
> -       spin_unlock(&vdpasim->lock);
> +       mutex_unlock(&vdpasim->mutex);
>
>         return 0;
>  }
> @@ -525,14 +525,14 @@ static int vdpasim_set_group_asid(struct vdpa_devic=
e *vdpa, unsigned int group,
>
>         iommu =3D &vdpasim->iommu[asid];
>
> -       spin_lock(&vdpasim->lock);
> +       mutex_lock(&vdpasim->mutex);
>
>         for (i =3D 0; i < vdpasim->dev_attr.nvqs; i++)
>                 if (vdpasim_get_vq_group(vdpa, i) =3D=3D 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 =3D 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 =3D 0, rx_overruns =3D 0, rx_errors =3D 0, tx_errors=
 =3D 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 +=3D tx_pkts;
> --
> 2.39.2
>