linux-kernel - Re: [PATCH V1] vdpa_sim: reset must not run

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Date: Fri, 9 Feb 2024 17:34:06 -0500
From: Steven Sistare <steven.sistare@...cle.com>
To: Stefano Garzarella <sgarzare@...hat.com>,
        Eugenio Perez Martin <eperezma@...hat.com>
Cc: virtualization@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>, Si-Wei Liu <si-wei.liu@...cle.com>
Subject: Re: [PATCH V1] vdpa_sim: reset must not run

On 1/22/2024 5:59 AM, Stefano Garzarella wrote:
> On Mon, Jan 22, 2024 at 11:47:22AM +0100, Eugenio Perez Martin wrote:
>> On Mon, Jan 22, 2024 at 11:22 AM Stefano Garzarella <sgarzare@...hat.com> wrote:
>>>
>>> On Wed, Jan 17, 2024 at 11:23:23AM -0800, Steve Sistare wrote:
>>> >vdpasim_do_reset sets running to true, which is wrong, as it allows
>>> >vdpasim_kick_vq to post work requests before the device has been
>>> >configured.  To fix, do not set running until VIRTIO_CONFIG_S_FEATURES_OK
>>> >is set.
>>> >
>>> >Fixes: 0c89e2a3a9d0 ("vdpa_sim: Implement suspend vdpa op")
>>> >Signed-off-by: Steve Sistare <steven.sistare@...cle.com>
>>> >Reviewed-by: Eugenio Pérez <eperezma@...hat.com>
>>> >---
>>> > drivers/vdpa/vdpa_sim/vdpa_sim.c | 3 ++-
>>> > 1 file changed, 2 insertions(+), 1 deletion(-)
>>> >
>>> >diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
>>> >index be2925d0d283..6304cb0b4770 100644
>>> >--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
>>> >+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
>>> >@@ -160,7 +160,7 @@ static void vdpasim_do_reset(struct vdpasim *vdpasim, u32 flags)
>>> >               }
>>> >       }
>>> >
>>> >-      vdpasim->running = true;
>>> >+      vdpasim->running = false;
>>> >       spin_unlock(&vdpasim->iommu_lock);
>>> >
>>> >       vdpasim->features = 0;
>>> >@@ -483,6 +483,7 @@ static void vdpasim_set_status(struct vdpa_device *vdpa, u8 status)
>>> >
>>> >       mutex_lock(&vdpasim->mutex);
>>> >       vdpasim->status = status;
>>> >+      vdpasim->running = (status & VIRTIO_CONFIG_S_FEATURES_OK) != 0;
>>> >       mutex_unlock(&vdpasim->mutex);
>>>
>>> Should we do something similar also in vdpasim_resume() ?
>>>
>>> I mean something like this:
>>>
>>> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
>>> index be2925d0d283..55e4633d5442 100644
>>> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
>>> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
>>> @@ -520,7 +520,7 @@ static int vdpasim_resume(struct vdpa_device *vdpa)
>>>          int i;
>>>
>>>          mutex_lock(&vdpasim->mutex);
>>> -       vdpasim->running = true;
>>> +       vdpasim->running = (vdpasim->status & VIRTIO_CONFIG_S_FEATURES_OK) != 0;
>>>
>>>          if (vdpasim->pending_kick) {
>>>                  /* Process pending descriptors */
>>>
>>> Thanks,
>>> Stefano
>>>
>>
>> The suspend and resume operation should not be called before
>> DRIVER_OK, so maybe we should add that protection at
>> drivers/vhost/vdpa.c actually?
> 
> Yeah, I think so!
> 
> Anyway, IMHO we should at least return an error in vdpa_sim if vdpasim_suspend/resume are called before DRIVER_OK (in another patch of course).

I submitted "vdpa: suspend and resume require DRIVER_OK" to check this in vdpa.c so there
is no need to check it in the leaf drivers.

I also submitted V2 of this patch, "vdpa_sim: reset must not run".
It checks for DRIVER_OK, instead of FEATURES_OK.

- Steve