linux-kernel - Re: [PATCH 1/2] vdpa_sim: not reset state in vdpasim_queue

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Message-ID: <CAPpAL=zh=0-0yN-kSynBphe2sat-B0zePckpZ8q7dtfYJxODzw@mail.gmail.com>
Date:   Tue, 31 Jan 2023 23:44:08 +0800
From:   Lei Yang <leiyang@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     Eugenio Perez Martin <eperezma@...hat.com>, mst@...hat.com,
        Laurent Vivier <lvivier@...hat.com>, sgarzare@...hat.com,
        Zhu Lingshan <lingshan.zhu@...el.com>,
        virtualization@...ts.linux-foundation.org, si-wei.liu@...cle.com,
        linux-kernel@...r.kernel.org, lulu@...hat.com,
        Gautam Dawar <gdawar@...inx.com>, alvaro.karsz@...id-run.com
Subject: Re: [PATCH 1/2] vdpa_sim: not reset state in vdpasim_queue_ready

The patch was tested by QE in a test environment and regression tested
using vdpa_sim device with virtio_vdpa and vhost_vdpa;There are no new
issues caused by this patch.

Tested-by: Lei Yang <leiyang@...hat.com>

Jason Wang <jasowang@...hat.com> 于2023年1月29日周日 13:56写道：
>
>
> 在 2023/1/19 17:14, Eugenio Perez Martin 写道:
> > On Thu, Jan 19, 2023 at 4:16 AM Jason Wang <jasowang@...hat.com> wrote:
> >> On Thu, Jan 19, 2023 at 12:44 AM Eugenio Pérez <eperezma@...hat.com> wrote:
> >>> vdpasim_queue_ready calls vringh_init_iotlb, which resets split indexes.
> >>> But it can be called after setting a ring base with
> >>> vdpasim_set_vq_state.
> >>>
> >>> Fix it by stashing them. They're still resetted in vdpasim_vq_reset.
> >>>
> >>> This was discovered and tested live migrating the vdpa_sim_net device.
> >>>
> >>> Fixes: 2c53d0f64c06 ("vdpasim: vDPA device simulator")
> >>> Signed-off-by: Eugenio Pérez <eperezma@...hat.com>
> >>> ---
> >>>   drivers/vdpa/vdpa_sim/vdpa_sim.c | 2 ++
> >>>   1 file changed, 2 insertions(+)
> >>>
> >>> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> >>> index cb88891b44a8..8839232a3fcb 100644
> >>> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
> >>> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> >>> @@ -66,6 +66,7 @@ static void vdpasim_vq_notify(struct vringh *vring)
> >>>   static void vdpasim_queue_ready(struct vdpasim *vdpasim, unsigned int idx)
> >>>   {
> >>>          struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
> >>> +       uint16_t last_avail_idx = vq->vring.last_avail_idx;
> >>>
> >>>          vringh_init_iotlb(&vq->vring, vdpasim->features, vq->num, false,
> >>>                            (struct vring_desc *)(uintptr_t)vq->desc_addr,
> >>> @@ -74,6 +75,7 @@ static void vdpasim_queue_ready(struct vdpasim *vdpasim, unsigned int idx)
> >>>                            (struct vring_used *)
> >>>                            (uintptr_t)vq->device_addr);
> >>>
> >>> +       vq->vring.last_avail_idx = last_avail_idx;
> >> Does this need to be serialized with the datapath?
> >>
> >> E.g in set_vq_state() we do:
> >>
> >> spin_lock(&vdpasim->lock);
> >> vrh->last_avail_idx = state->split.avail_index;
> >> spin_unlock(&vdpasim->lock);
> >>
> > vdpasim_queue_ready is called from vdpasim_set_vq_ready, which holds
> > these locks.
> >
> > Maybe it's too much indirection and to embed vdpasim_queue_ready in
> > vdpasim_set_vq_ready would be clearer for the future?
>
>
> Nope, I miss the caller.
>
> Acked-by: Jason Wang <jasowang@...hat.com>
>
> Thanks
>
>
> >
> > Thanks!
> >
>