linux-kernel - Re: [PATCH V3 3/3] vdpa_sim: flush workers on suspend

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Message-ID: <CACGkMEtVt+W4jmBxaXAytreXjJUHxmo+zzAw0wsrLw97pJmW-A@mail.gmail.com>
Date: Wed, 22 May 2024 11:39:41 +0800
From: Jason Wang <jasowang@...hat.com>
To: Steven Sistare <steven.sistare@...cle.com>
Cc: virtualization@...ts.linux-foundation.org, linux-kernel@...r.kernel.org, 
	"Michael S. Tsirkin" <mst@...hat.com>, Si-Wei Liu <si-wei.liu@...cle.com>, 
	Eugenio Perez Martin <eperezma@...hat.com>, Xie Yongji <xieyongji@...edance.com>, 
	Stefano Garzarella <sgarzare@...hat.com>
Subject: Re: [PATCH V3 3/3] vdpa_sim: flush workers on suspend

On Tue, May 21, 2024 at 9:39 PM Steven Sistare
<steven.sistare@...cle.com> wrote:
>
> On 5/20/2024 10:32 PM, Jason Wang wrote:
> > On Mon, May 20, 2024 at 11:21 PM Steve Sistare
> > <steven.sistare@...cle.com> wrote:
> >>
> >> Flush to guarantee no workers are running when suspend returns.
> >> Add a lock to enforce ordering between clearing running, flushing,
> >> and posting new work in vdpasim_kick_vq.  It must be a spin lock
> >> because vdpasim_kick_vq may be reached va eventfd_write.
> >>
> >> Signed-off-by: Steve Sistare <steven.sistare@...cle.com>
> >> ---
> >>   drivers/vdpa/vdpa_sim/vdpa_sim.c | 16 ++++++++++++++--
> >>   drivers/vdpa/vdpa_sim/vdpa_sim.h |  1 +
> >>   2 files changed, 15 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> >> index 8ffea8430f95..67ed49d95bf0 100644
> >> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
> >> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> >> @@ -322,7 +322,7 @@ static u16 vdpasim_get_vq_size(struct vdpa_device *vdpa, u16 idx)
> >>                  return VDPASIM_QUEUE_MAX;
> >>   }
> >>
> >> -static void vdpasim_kick_vq(struct vdpa_device *vdpa, u16 idx)
> >> +static void vdpasim_do_kick_vq(struct vdpa_device *vdpa, u16 idx)
> >>   {
> >>          struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
> >>          struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
> >> @@ -337,6 +337,15 @@ static void vdpasim_kick_vq(struct vdpa_device *vdpa, u16 idx)
> >>                  vdpasim_schedule_work(vdpasim);
> >>   }
> >>
> >> +static void vdpasim_kick_vq(struct vdpa_device *vdpa, u16 idx)
> >> +{
> >> +       struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
> >> +
> >> +       spin_lock(&vdpasim->kick_lock);
> >> +       vdpasim_do_kick_vq(vdpa, idx);
> >> +       spin_unlock(&vdpasim->kick_lock);
> >> +}
> >> +
> >>   static void vdpasim_set_vq_cb(struct vdpa_device *vdpa, u16 idx,
> >>                                struct vdpa_callback *cb)
> >>   {
> >> @@ -520,8 +529,11 @@ static int vdpasim_suspend(struct vdpa_device *vdpa)
> >>          struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
> >>
> >>          mutex_lock(&vdpasim->mutex);
> >> +       spin_lock(&vdpasim->kick_lock);
> >>          vdpasim->running = false;
> >> +       spin_unlock(&vdpasim->kick_lock);
> >>          mutex_unlock(&vdpasim->mutex);
> >> +       kthread_flush_work(&vdpasim->work);
> >>
> >>          return 0;
> >>   }
> >> @@ -537,7 +549,7 @@ static int vdpasim_resume(struct vdpa_device *vdpa)
> >>          if (vdpasim->pending_kick) {
> >>                  /* Process pending descriptors */
> >>                  for (i = 0; i < vdpasim->dev_attr.nvqs; ++i)
> >> -                       vdpasim_kick_vq(vdpa, i);
> >> +                       vdpasim_do_kick_vq(vdpa, i);
> >>
> >>                  vdpasim->pending_kick = false;
> >>          }
> >> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.h b/drivers/vdpa/vdpa_sim/vdpa_sim.h
> >> index bb137e479763..5eb6ca9c5ec5 100644
> >> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.h
> >> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.h
> >> @@ -75,6 +75,7 @@ struct vdpasim {
> >>          bool pending_kick;
> >>          /* spinlock to synchronize iommu table */
> >>          spinlock_t iommu_lock;
> >> +       spinlock_t kick_lock;
> >
> > It looks to me this is not initialized?
>
> Yup, I lost that line while fiddling with different locking schemes.
> Thanks, will fix in V4.
>
> @@ -236,6 +236,7 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr
> *dev_attr,
>
>          mutex_init(&vdpasim->mutex);
>          spin_lock_init(&vdpasim->iommu_lock);
> +       spin_lock_init(&vdpasim->kick_lock);
>
> With that fix, does this patch earn your RB?

Yes.

Thanks

>
> - Steve
>
> >>   };
> >>
> >>   struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *attr,
> >> --
> >> 2.39.3
> >>
> >
>