From: Jason Wang <jasowang@redhat.com>
To: Yongji Xie <xieyongji@bytedance.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
Stefano Garzarella <sgarzare@redhat.com>,
Parav Pandit <parav@nvidia.com>, Bob Liu <bob.liu@oracle.com>,
Christoph Hellwig <hch@infradead.org>,
Randy Dunlap <rdunlap@infradead.org>,
Matthew Wilcox <willy@infradead.org>,
viro@zeniv.linux.org.uk, Jens Axboe <axboe@kernel.dk>,
bcrl@kvack.org, Jonathan Corbet <corbet@lwn.net>,
virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, kvm@vger.kernel.org, linux-aio@kvack.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [RFC v3 08/11] vduse: Introduce VDUSE - vDPA Device in Userspace
Date: Thu, 28 Jan 2021 14:14:33 +0800 [thread overview]
Message-ID: <bdb57829-d4a4-eaca-d43b-70d39df96bf6@redhat.com> (raw)
In-Reply-To: <CACycT3upvTrkm5Cd6KzphSk=FYDjAVCbFJ0CLmha5sP_h=5KGg@mail.gmail.com>
On 2021/1/28 下午2:03, Yongji Xie wrote:
>>>>> +
>>>>> +static const struct file_operations vduse_domain_fops = {
>>>>> + .mmap = vduse_domain_mmap,
>>>>> + .release = vduse_domain_release,
>>>>> +};
>>>> It's better to explain the reason for introducing a dedicated file for
>>>> mmap() here.
>>>>
>>> To make the implementation of iova_domain independent with vduse_dev.
>> My understanding is that, the only usage for this is to:
>>
>> 1) support different type of iova mappings
>> 2) or switch between iova domain mappings
>>
>> But I can't think of a need for this.
>>
> For example, share one iova_domain between several vduse devices.
Interesting.
>
> And it will be helpful if we want to split this patch into iova domain
> part and vduse device part. Because the page fault handler should be
> paired with dma_map/dma_unmap.
Ok.
[...]
>
>>>> This looks not safe, let's use idr here.
>>>>
>>> Could you give more details? Looks like idr should not used in this
>>> case which can not tolerate failure. And using a list to store the msg
>>> is better than using idr when the msg needs to be re-inserted in some
>>> cases.
>> My understanding is the "unique" (probably need a better name) is a
>> token that is used to uniquely identify a message. The reply from
>> userspace is required to write with exact the same token(unique). IDR
>> seems better but consider we can hardly hit 64bit overflow, atomic might
>> be OK as well.
>>
>> Btw, under what case do we need to do "re-inserted"?
>>
> When userspace daemon receive the message but doesn't reply it before crash.
Do we have code to do this?
[...]
>
>>>> So we had multiple types of requests/responses, is this better to
>>>> introduce a queue based admin interface other than ioctl?
>>>>
>>> Sorry, I didn't get your point. What do you mean by queue-based admin
>>> interface? Virtqueue-based?
>> Yes, a queue(virtqueue). The commands could be passed through the queue.
>> (Just an idea, not sure it's worth)
>>
> I considered it before. But I found it still needs some extra works
> (setup eventfd, set vring base and so on) to setup the admin virtqueue
> before using it for communication. So I turn to use this simple way.
Yes. We might consider it in the future.
[...]
>
>>>> Any reason for such IOTLB invalidation here?
>>>>
>>> As I mentioned before, this is used to notify userspace to update the
>>> IOTLB. Mainly for virtio-vdpa case.
>> So the question is, usually, there could be several times of status
>> setting during driver initialization. Do we really need to update IOTLB
>> every time?
>>
> I think we can check whether there are some changes after the last
> IOTLB updating here.
So the question still, except reset (write 0), any other status that can
affect IOTLB?
[...]
>
>> Something like swiotlb default value (64M)?
>>
> Do we need a module parameter to change it?
We can.
[...]
>
>>>>> + union {
>>>>> + struct vduse_vq_num vq_num; /* virtqueue num */
>>>>> + struct vduse_vq_addr vq_addr; /* virtqueue address */
>>>>> + struct vduse_vq_ready vq_ready; /* virtqueue ready status */
>>>>> + struct vduse_vq_state vq_state; /* virtqueue state */
>>>>> + struct vduse_dev_config_data config; /* virtio device config space */
>>>>> + struct vduse_iova_range iova; /* iova range for updating */
>>>>> + __u64 features; /* virtio features */
>>>>> + __u8 status; /* device status */
>>>> Let's add some padding for future extensions.
>>>>
>>> Is sizeof(vduse_dev_config_data) ok? Or char[1024]?
>> 1024 seems too large, 128 or 256 looks better.
>>
> If so, sizeof(vduse_dev_config_data) is enough.
Ok if we don't need a message more than that in the future.
Thanks
next prev parent reply other threads:[~2021-01-28 6:16 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-19 4:59 [RFC v3 00/11] Introduce VDUSE - vDPA Device in Userspace Xie Yongji
2021-01-19 4:59 ` [RFC v3 01/11] eventfd: track eventfd_signal() recursion depth separately in different cases Xie Yongji
2021-01-20 4:24 ` Jason Wang
2021-01-20 6:52 ` Yongji Xie
2021-01-27 3:37 ` Jason Wang
2021-01-27 9:11 ` Yongji Xie
2021-01-28 3:04 ` Jason Wang
2021-01-28 3:08 ` Jens Axboe
2021-01-28 5:12 ` Yongji Xie
2021-01-28 3:52 ` Yongji Xie
2021-01-28 4:31 ` Jason Wang
2021-01-28 6:08 ` Yongji Xie
2021-01-19 4:59 ` [RFC v3 02/11] eventfd: Increase the recursion depth of eventfd_signal() Xie Yongji
2021-01-19 4:59 ` [RFC v3 03/11] vdpa: Remove the restriction that only supports virtio-net devices Xie Yongji
2021-01-20 3:46 ` Jason Wang
2021-01-20 6:46 ` Yongji Xie
2021-01-20 11:08 ` Stefano Garzarella
2021-01-27 3:33 ` Jason Wang
2021-01-27 8:57 ` Stefano Garzarella
2021-01-28 3:11 ` Jason Wang
[not found] ` <20210129150359.caitcskrfhqed73z@steredhat>
2021-01-30 11:33 ` Yongji Xie
2021-02-01 11:05 ` Stefano Garzarella
2021-01-27 8:59 ` Stefano Garzarella
2021-01-27 9:05 ` Yongji Xie
2021-01-19 4:59 ` [RFC v3 04/11] vhost-vdpa: protect concurrent access to vhost device iotlb Xie Yongji
2021-01-20 3:44 ` Jason Wang
2021-01-20 6:44 ` Yongji Xie
2021-01-19 4:59 ` [RFC v3 05/11] vdpa: shared virtual addressing support Xie Yongji
2021-01-20 5:55 ` Jason Wang
2021-01-20 7:10 ` Yongji Xie
2021-01-27 3:43 ` Jason Wang
2021-01-19 4:59 ` [RFC v3 06/11] vhost-vdpa: Add an opaque pointer for vhost IOTLB Xie Yongji
2021-01-20 6:24 ` Jason Wang
2021-01-20 7:52 ` Yongji Xie
2021-01-27 3:51 ` Jason Wang
2021-01-27 9:27 ` Yongji Xie
2021-01-19 5:07 ` [RFC v3 07/11] vdpa: Pass the netlink attributes to ops.dev_add() Xie Yongji
2021-01-19 5:07 ` [RFC v3 08/11] vduse: Introduce VDUSE - vDPA Device in Userspace Xie Yongji
2021-01-19 14:53 ` Jonathan Corbet
2021-01-20 2:25 ` Yongji Xie
2021-01-19 17:53 ` Randy Dunlap
2021-01-20 2:42 ` Yongji Xie
2021-01-26 8:08 ` Jason Wang
2021-01-27 8:50 ` Yongji Xie
2021-01-28 4:27 ` Jason Wang
2021-01-28 6:03 ` Yongji Xie
2021-01-28 6:14 ` Jason Wang [this message]
2021-01-28 6:43 ` Yongji Xie
2021-01-26 8:19 ` Jason Wang
2021-01-27 8:59 ` Yongji Xie
2021-01-19 5:07 ` [RFC v3 09/11] vduse: Add VDUSE_GET_DEV ioctl Xie Yongji
2021-01-19 5:07 ` [RFC v3 10/11] vduse: grab the module's references until there is no vduse device Xie Yongji
2021-01-26 8:09 ` Jason Wang
2021-01-27 8:51 ` Yongji Xie
2021-01-19 5:07 ` [RFC v3 11/11] vduse: Introduce a workqueue for irq injection Xie Yongji
2021-01-26 8:17 ` Jason Wang
2021-01-27 9:00 ` Yongji Xie
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