From: Yongji Xie <xieyongji@bytedance.com>
To: Jason Wang <jasowang@redhat.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: Re: [PATCH v6 09/10] vduse: Introduce VDUSE - vDPA Device in Userspace
Date: Tue, 13 Apr 2021 12:28:21 +0800 [thread overview]
Message-ID: <CACycT3tHxtfgQhQgv0VyF_U523qASEv1Ydc4XuX43MFRzGVbfw@mail.gmail.com> (raw)
In-Reply-To: <a85c0a66-ad7f-a344-f8ed-363355f5e283@redhat.com>
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
next prev parent reply other threads:[~2021-04-13 4:28 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 [this message]
2021-04-14 8:18 ` Jason Wang
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
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