netdev - Re: [PATCH v2 2/8] vhost-vdpa: use bind_mm/unbind

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Date:   Thu, 16 Mar 2023 09:31:22 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     virtualization@...ts.linux-foundation.org,
        Andrey Zhadchenko <andrey.zhadchenko@...tuozzo.com>,
        eperezma@...hat.com, netdev@...r.kernel.org, stefanha@...hat.com,
        linux-kernel@...r.kernel.org,
        "Michael S. Tsirkin" <mst@...hat.com>, kvm@...r.kernel.org
Subject: Re: [PATCH v2 2/8] vhost-vdpa: use bind_mm/unbind_mm device callbacks

On Tue, Mar 14, 2023 at 11:48:33AM +0800, Jason Wang wrote:
>On Thu, Mar 2, 2023 at 7:34 PM Stefano Garzarella <sgarzare@...hat.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@...hat.com>
>> ---
>>
>> Notes:
>>     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 | 30 ++++++++++++++++++++++++++++++
>>  1 file changed, 30 insertions(+)
>>
>> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
>> index dc12dbd5b43b..1ab89fccd825 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;
>> @@ -711,6 +733,13 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
>>                 break;
>>         default:
>>                 r = vhost_dev_ioctl(&v->vdev, cmd, argp);
>> +               if (!r && cmd == VHOST_SET_OWNER) {
>> +                       r = vhost_vdpa_bind_mm(v);
>> +                       if (r) {
>> +                               vhost_dev_reset_owner(&v->vdev, NULL);
>> +                               break;
>> +                       }
>> +               }
>
>Nit: is it better to have a new condition/switch branch instead of
>putting them under default? (as what vring_ioctl did).

Yep, I agree!

I'll change it.

Thanks,
Stefano