Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20221205084127.535-1-xieyongji@bytedance.com> <20221205084127.535-6-xieyongji@bytedance.com>
In-Reply-To: <20221205084127.535-6-xieyongji@bytedance.com>
From:   Jason Wang <jasowang@redhat.com>
Date:   Fri, 16 Dec 2022 12:02:38 +0800
Message-ID: <CACGkMEvkTJn7Hm5u=79nDNHQG_gakS3Cbvi=JpO38ndjHy_fog@mail.gmail.com>
Subject: Re: [PATCH v2 05/11] vduse: Introduce bound workqueue for irq injection
To:     Xie Yongji <xieyongji@bytedance.com>
Cc:     mst@redhat.com, tglx@linutronix.de, hch@lst.de,
        virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Mon, Dec 5, 2022 at 4:44 PM Xie Yongji <xieyongji@bytedance.com> wrote:
>
> This introduces a bound workqueue to support running
> irq callback in a specified cpu.
>
> Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> ---
>  drivers/vdpa/vdpa_user/vduse_dev.c | 29 ++++++++++++++++++++++-------
>  1 file changed, 22 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index 37809bfcb7ef..d126f3e32a20 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -57,6 +57,7 @@ struct vduse_virtqueue {
>         struct vdpa_callback cb;
>         struct work_struct inject;
>         struct work_struct kick;
> +       int irq_effective_cpu;

I wonder why it's a cpu number instead of a cpumask. The latter seems
more flexible, e.g when using NUMA.

>  };
>
>  struct vduse_dev;
> @@ -128,6 +129,7 @@ static struct class *vduse_class;
>  static struct cdev vduse_ctrl_cdev;
>  static struct cdev vduse_cdev;
>  static struct workqueue_struct *vduse_irq_wq;
> +static struct workqueue_struct *vduse_irq_bound_wq;
>
>  static u32 allowed_device_id[] = {
>         VIRTIO_ID_BLOCK,
> @@ -917,7 +919,8 @@ static void vduse_vq_irq_inject(struct work_struct *work)
>  }
>
>  static int vduse_dev_queue_irq_work(struct vduse_dev *dev,
> -                                   struct work_struct *irq_work)
> +                                   struct work_struct *irq_work,
> +                                   int irq_effective_cpu)
>  {
>         int ret = -EINVAL;
>
> @@ -926,7 +929,11 @@ static int vduse_dev_queue_irq_work(struct vduse_dev *dev,
>                 goto unlock;
>
>         ret = 0;
> -       queue_work(vduse_irq_wq, irq_work);
> +       if (irq_effective_cpu == -1)

Is it better to have a macro for this magic number?

Thanks