linux-kernel - Re: [RFC PATCH 1/6] vdpa: add bind

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Message-ID: <bd1c0fea-9934-1956-b3fe-0442d90b0477@redhat.com>
Date:   Thu, 22 Dec 2022 12:18:15 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     virtualization@...ts.linux-foundation.org,
        Andrey Zhadchenko <andrey.zhadchenko@...tuozzo.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        "Michael S. Tsirkin" <mst@...hat.com>, eperezma@...hat.com,
        stefanha@...hat.com, netdev@...r.kernel.org
Subject: Re: [RFC PATCH 1/6] vdpa: add bind_mm callback


在 2022/12/16 16:17, Stefano Garzarella 写道:
> On Fri, Dec 16, 2022 at 02:37:45PM +0800, Jason Wang wrote:
>> On Thu, Dec 15, 2022 at 12:30 AM Stefano Garzarella 
>> <sgarzare@...hat.com> wrote:
>>>
>>> This new optional callback is used to bind the device to a specific
>>> address space so the vDPA framework can use VA when this callback
>>> is implemented.
>>>
>>> Suggested-by: Jason Wang <jasowang@...hat.com>
>>> Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
>>> ---
>>>  include/linux/vdpa.h | 8 ++++++++
>>>  1 file changed, 8 insertions(+)
>>>
>>> diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
>>> index 6d0f5e4e82c2..34388e21ef3f 100644
>>> --- a/include/linux/vdpa.h
>>> +++ b/include/linux/vdpa.h
>>> @@ -282,6 +282,12 @@ struct vdpa_map_file {
>>>   *                             @iova: iova to be unmapped
>>>   *                             @size: size of the area
>>>   *                             Returns integer: success (0) or 
>>> error (< 0)
>>> + * @bind_mm:                   Bind the device to a specific 
>>> address space
>>> + *                             so the vDPA framework can use VA 
>>> when this
>>> + *                             callback is implemented. (optional)
>>> + *                             @vdev: vdpa device
>>> + *                             @mm: address space to bind
>>
>> Do we need an unbind or did a NULL mm mean unbind?
>
> Yep, your comment in patch 6 makes it necessary. I will add it!
>
>>
>>> + *                             @owner: process that owns the 
>>> address space
>>
>> Any reason we need the task_struct here?
>
> Mainly to attach to kthread to the process cgroups, but that part is 
> still in TODO since I need to understand it better.


Ok I see.


>
> Maybe we can remove the task_struct here and use `current` directly in 
> the callback.


Yes, it's easier to start without cgroup and we can add it on top.

Thanks


>
> Thanks,
> Stefano
>