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

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Date:   Sun, 29 Jan 2023 13:56:06 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Eugenio Perez Martin <eperezma@...hat.com>
Cc:     mst@...hat.com, leiyang@...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


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!
>