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Date:   Thu, 23 Mar 2023 10:38:37 +0100
From:   Stefano Garzarella <sgarzare@redhat.com>
To:     Jason Wang <jasowang@redhat.com>
Cc:     virtualization@lists.linux-foundation.org, stefanha@redhat.com,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Andrey Zhadchenko <andrey.zhadchenko@virtuozzo.com>,
        eperezma@redhat.com, netdev@vger.kernel.org, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 2/8] vhost-vdpa: use bind_mm/unbind_mm device callbacks
Message-ID: <20230323093837.xdv7wkhzizgnihcy@sgarzare-redhat>
References: <20230321154228.182769-1-sgarzare@redhat.com>
 <20230321154228.182769-3-sgarzare@redhat.com>
 <CACGkMEtq8PWL01WBL2Ve-Yr=ZO+su73tKuOh1EBLagkrLdiCaQ@mail.gmail.com>
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On Thu, Mar 23, 2023 at 11:01:39AM +0800, Jason Wang wrote:
>On Tue, Mar 21, 2023 at 11:42 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
>>
>> When the user call VHOST_SET_OWNER ioctl and the vDPA device
>> has `use_va` set to true, let's call the bind_mm callback.
>> In this way we can bind the device to the user address space
>> and directly use the user VA.
>>
>> The unbind_mm callback is called during the release after
>> stopping the device.
>>
>> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
>> ---
>>
>> Notes:
>>     v3:
>>     - added `case VHOST_SET_OWNER` in vhost_vdpa_unlocked_ioctl() [Jason]
>>     v2:
>>     - call the new unbind_mm callback during the release [Jason]
>>     - avoid to call bind_mm callback after the reset, since the device
>>       is not detaching it now during the reset
>>
>>  drivers/vhost/vdpa.c | 31 +++++++++++++++++++++++++++++++
>>  1 file changed, 31 insertions(+)
>>
>> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
>> index 7be9d9d8f01c..20250c3418b2 100644
>> --- a/drivers/vhost/vdpa.c
>> +++ b/drivers/vhost/vdpa.c
>> @@ -219,6 +219,28 @@ static int vhost_vdpa_reset(struct vhost_vdpa *v)
>>         return vdpa_reset(vdpa);
>>  }
>>
>> +static long vhost_vdpa_bind_mm(struct vhost_vdpa *v)
>> +{
>> +       struct vdpa_device *vdpa = v->vdpa;
>> +       const struct vdpa_config_ops *ops = vdpa->config;
>> +
>> +       if (!vdpa->use_va || !ops->bind_mm)
>> +               return 0;
>> +
>> +       return ops->bind_mm(vdpa, v->vdev.mm);
>> +}
>> +
>> +static void vhost_vdpa_unbind_mm(struct vhost_vdpa *v)
>> +{
>> +       struct vdpa_device *vdpa = v->vdpa;
>> +       const struct vdpa_config_ops *ops = vdpa->config;
>> +
>> +       if (!vdpa->use_va || !ops->unbind_mm)
>> +               return;
>> +
>> +       ops->unbind_mm(vdpa);
>> +}
>> +
>>  static long vhost_vdpa_get_device_id(struct vhost_vdpa *v, u8 __user *argp)
>>  {
>>         struct vdpa_device *vdpa = v->vdpa;
>> @@ -709,6 +731,14 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
>>         case VHOST_VDPA_RESUME:
>>                 r = vhost_vdpa_resume(v);
>>                 break;
>> +       case VHOST_SET_OWNER:
>> +               r = vhost_dev_set_owner(d);
>
>Nit:
>
>I'd stick to the current way of passing the cmd, argp to
>vhost_dev_ioctl() and introduce a new switch after the
>vhost_dev_ioctl().
>
>In this way, we are immune to any possible changes of dealing with
>VHOST_SET_OWNER in vhost core.

Good point, I'll change in v4.

>
>Others look good.

Thanks,
Stefano