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>,
"Christoph Hellwig" <hch@infradead.org>,
"Christian Brauner" <christian.brauner@canonical.com>,
"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>,
"Mika Penttilä" <mika.penttila@nextfour.com>,
"Dan Carpenter" <dan.carpenter@oracle.com>,
virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, kvm@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v6 09/10] vduse: Introduce VDUSE - vDPA Device in Userspace
Date: Wed, 14 Apr 2021 16:18:11 +0800 [thread overview]
Message-ID: <51cd2e3a-5b76-a6f5-da59-b118a7e13923@redhat.com> (raw)
In-Reply-To: <CACycT3tHxtfgQhQgv0VyF_U523qASEv1Ydc4XuX43MFRzGVbfw@mail.gmail.com>
在 2021/4/13 下午12:28, Yongji Xie 写道:
> On Tue, Apr 13, 2021 at 11:35 AM Jason Wang <jasowang@redhat.com> wrote:
>>
>> 在 2021/4/12 下午5:59, Yongji Xie 写道:
>>> On Mon, Apr 12, 2021 at 5:37 PM Jason Wang <jasowang@redhat.com> wrote:
>>>> 在 2021/4/12 下午4:02, Yongji Xie 写道:
>>>>> On Mon, Apr 12, 2021 at 3:16 PM Jason Wang <jasowang@redhat.com> wrote:
>>>>>> 在 2021/4/9 下午4:02, Yongji Xie 写道:
>>>>>>>>>>> +};
>>>>>>>>>>> +
>>>>>>>>>>> +struct vduse_dev_config_data {
>>>>>>>>>>> + __u32 offset; /* offset from the beginning of config space */
>>>>>>>>>>> + __u32 len; /* the length to read/write */
>>>>>>>>>>> + __u8 data[VDUSE_CONFIG_DATA_LEN]; /* data buffer used to read/write */
>>>>>>>>>> Note that since VDUSE_CONFIG_DATA_LEN is part of uAPI it means we can
>>>>>>>>>> not change it in the future.
>>>>>>>>>>
>>>>>>>>>> So this might suffcient for future features or all type of virtio devices.
>>>>>>>>>>
>>>>>>>>> Do you mean 256 is no enough here?
>>>>>>>> Yes.
>>>>>>>>
>>>>>>> But this request will be submitted multiple times if config lengh is
>>>>>>> larger than 256. So do you think whether we need to extent the size to
>>>>>>> 512 or larger?
>>>>>> So I think you'd better either:
>>>>>>
>>>>>> 1) document the limitation (256) in somewhere, (better both uapi and doc)
>>>>>>
>>>>> But the VDUSE_CONFIG_DATA_LEN doesn't mean the limitation of
>>>>> configuration space. It only means the maximum size of one data
>>>>> transfer for configuration space. Do you mean document this?
>>>> Yes, and another thing is that since you're using
>>>> data[VDUSE_CONFIG_DATA_LEN] in the uapi, it implies the length is always
>>>> 256 which seems not good and not what the code is wrote.
>>>>
>>> How about renaming VDUSE_CONFIG_DATA_LEN to VDUSE_MAX_TRANSFER_LEN?
>>>
>>> Thanks,
>>> Yongji
>>
>> So a question is the reason to have a limitation of this in the uAPI?
>> Note that in vhost-vdpa we don't have such:
>>
>> struct vhost_vdpa_config {
>> __u32 off;
>> __u32 len;
>> __u8 buf[0];
>> };
>>
> If so, we need to call read()/write() multiple times each time
> receiving/sending one request or response in userspace and kernel. For
> example,
>
> 1. read and check request/response type
> 2. read and check config length if type is VDUSE_SET_CONFIG or VDUSE_GET_CONFIG
> 3. read the payload
>
> Not sure if it's worth it.
>
> Thanks,
> Yongji
Right, I see.
So I'm fine with current approach.
Thanks
>
next prev parent reply other threads:[~2021-04-14 8:18 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-31 8:05 [PATCH v6 00/10] Introduce VDUSE - vDPA Device in Userspace Xie Yongji
2021-03-31 8:05 ` [PATCH v6 01/10] file: Export receive_fd() to modules Xie Yongji
2021-03-31 9:15 ` Christian Brauner
2021-03-31 9:26 ` Dan Carpenter
2021-03-31 9:28 ` Christian Brauner
2021-03-31 11:32 ` Yongji Xie
2021-03-31 12:23 ` Christian Brauner
2021-03-31 13:59 ` Yongji Xie
2021-03-31 14:07 ` Christian Brauner
2021-03-31 14:37 ` Yongji Xie
2021-03-31 8:05 ` [PATCH v6 02/10] eventfd: Increase the recursion depth of eventfd_signal() Xie Yongji
2021-03-31 8:05 ` [PATCH v6 03/10] vhost-vdpa: protect concurrent access to vhost device iotlb Xie Yongji
2021-04-09 16:15 ` Michael S. Tsirkin
2021-04-11 5:36 ` Yongji Xie
2021-04-11 20:48 ` Michael S. Tsirkin
2021-04-12 2:29 ` Yongji Xie
2021-04-12 9:00 ` Michael S. Tsirkin
2021-03-31 8:05 ` [PATCH v6 04/10] vhost-iotlb: Add an opaque pointer for vhost IOTLB Xie Yongji
2021-03-31 8:05 ` [PATCH v6 05/10] vdpa: Add an opaque pointer for vdpa_config_ops.dma_map() Xie Yongji
2021-03-31 8:05 ` [PATCH v6 06/10] vdpa: factor out vhost_vdpa_pa_map() and vhost_vdpa_pa_unmap() Xie Yongji
2021-03-31 8:05 ` [PATCH v6 07/10] vdpa: Support transferring virtual addressing during DMA mapping Xie Yongji
2021-04-08 2:36 ` Jason Wang
2021-03-31 8:05 ` [PATCH v6 08/10] vduse: Implement an MMU-based IOMMU driver Xie Yongji
2021-04-08 3:25 ` Jason Wang
2021-04-08 5:27 ` Yongji Xie
2021-03-31 8:05 ` [PATCH v6 09/10] vduse: Introduce VDUSE - vDPA Device in Userspace Xie Yongji
2021-04-08 6:57 ` Jason Wang
2021-04-08 9:36 ` Yongji Xie
2021-04-09 5:36 ` Jason Wang
2021-04-09 8:02 ` Yongji Xie
2021-04-12 7:16 ` Jason Wang
2021-04-12 8:02 ` Yongji Xie
2021-04-12 9:37 ` Jason Wang
2021-04-12 9:59 ` Yongji Xie
2021-04-13 3:35 ` Jason Wang
2021-04-13 4:28 ` Yongji Xie
2021-04-14 8:18 ` Jason Wang [this message]
2021-04-16 3:24 ` Jason Wang
2021-04-16 8:43 ` Yongji Xie
2021-03-31 8:05 ` [PATCH v6 10/10] Documentation: Add documentation for VDUSE Xie Yongji
2021-04-08 7:18 ` Jason Wang
2021-04-08 8:09 ` Yongji Xie
2021-04-14 14:14 ` Stefan Hajnoczi
2021-04-15 5:38 ` Yongji Xie
2021-04-15 7:19 ` Stefan Hajnoczi
2021-04-15 8:33 ` Yongji Xie
2021-04-15 14:17 ` Stefan Hajnoczi
2021-04-15 8:36 ` Jason Wang
2021-04-15 9:04 ` Jason Wang
2021-04-15 11:17 ` Yongji Xie
2021-04-16 2:20 ` Jason Wang
2021-04-16 2:58 ` Yongji Xie
2021-04-16 3:02 ` Jason Wang
2021-04-16 3:18 ` Yongji Xie
2021-04-15 14:38 ` Stefan Hajnoczi
2021-04-16 2:23 ` Jason Wang
2021-04-16 3:19 ` Yongji Xie
2021-04-16 5:39 ` Jason Wang
2021-04-16 3:13 ` Yongji Xie
2021-04-14 7:34 ` [PATCH v6 00/10] Introduce VDUSE - vDPA Device in Userspace Michael S. Tsirkin
2021-04-14 7:49 ` Jason Wang
2021-04-14 7:54 ` Yongji Xie
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=51cd2e3a-5b76-a6f5-da59-b118a7e13923@redhat.com \
--to=jasowang@redhat.com \
--cc=axboe@kernel.dk \
--cc=bcrl@kvack.org \
--cc=christian.brauner@canonical.com \
--cc=corbet@lwn.net \
--cc=dan.carpenter@oracle.com \
--cc=hch@infradead.org \
--cc=kvm@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=mika.penttila@nextfour.com \
--cc=mst@redhat.com \
--cc=netdev@vger.kernel.org \
--cc=parav@nvidia.com \
--cc=rdunlap@infradead.org \
--cc=sgarzare@redhat.com \
--cc=stefanha@redhat.com \
--cc=viro@zeniv.linux.org.uk \
--cc=virtualization@lists.linux-foundation.org \
--cc=willy@infradead.org \
--cc=xieyongji@bytedance.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).