From: Jason Wang <jasowang@redhat.com>
To: Yongji Xie <xieyongji@bytedance.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
sgarzare@redhat.com, Parav Pandit <parav@nvidia.com>,
akpm@linux-foundation.org, Randy Dunlap <rdunlap@infradead.org>,
Matthew Wilcox <willy@infradead.org>,
viro@zeniv.linux.org.uk, axboe@kernel.dk, bcrl@kvack.org,
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, linux-mm@kvack.org
Subject: Re: [RFC v2 09/13] vduse: Add support for processing vhost iotlb message
Date: Fri, 25 Dec 2020 14:57:59 +0800 [thread overview]
Message-ID: <0e6faf9c-117a-e23c-8d6d-488d0ec37412@redhat.com> (raw)
In-Reply-To: <CACycT3s=m=PQb5WFoMGhz8TNGme4+=rmbbBTtrugF9ZmNnWxEw@mail.gmail.com>
On 2020/12/24 下午3:37, Yongji Xie wrote:
> On Thu, Dec 24, 2020 at 10:41 AM Jason Wang <jasowang@redhat.com> wrote:
>>
>> On 2020/12/23 下午8:14, Yongji Xie wrote:
>>> On Wed, Dec 23, 2020 at 5:05 PM Jason Wang <jasowang@redhat.com> wrote:
>>>> On 2020/12/22 下午10:52, Xie Yongji wrote:
>>>>> To support vhost-vdpa bus driver, we need a way to share the
>>>>> vhost-vdpa backend process's memory with the userspace VDUSE process.
>>>>>
>>>>> This patch tries to make use of the vhost iotlb message to achieve
>>>>> that. We will get the shm file from the iotlb message and pass it
>>>>> to the userspace VDUSE process.
>>>>>
>>>>> Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
>>>>> ---
>>>>> Documentation/driver-api/vduse.rst | 15 +++-
>>>>> drivers/vdpa/vdpa_user/vduse_dev.c | 147 ++++++++++++++++++++++++++++++++++++-
>>>>> include/uapi/linux/vduse.h | 11 +++
>>>>> 3 files changed, 171 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/Documentation/driver-api/vduse.rst b/Documentation/driver-api/vduse.rst
>>>>> index 623f7b040ccf..48e4b1ba353f 100644
>>>>> --- a/Documentation/driver-api/vduse.rst
>>>>> +++ b/Documentation/driver-api/vduse.rst
>>>>> @@ -46,13 +46,26 @@ The following types of messages are provided by the VDUSE framework now:
>>>>>
>>>>> - VDUSE_GET_CONFIG: Read from device specific configuration space
>>>>>
>>>>> +- VDUSE_UPDATE_IOTLB: Update the memory mapping in device IOTLB
>>>>> +
>>>>> +- VDUSE_INVALIDATE_IOTLB: Invalidate the memory mapping in device IOTLB
>>>>> +
>>>>> Please see include/linux/vdpa.h for details.
>>>>>
>>>>> -In the data path, VDUSE framework implements a MMU-based on-chip IOMMU
>>>>> +The data path of userspace vDPA device is implemented in different ways
>>>>> +depending on the vdpa bus to which it is attached.
>>>>> +
>>>>> +In virtio-vdpa case, VDUSE framework implements a MMU-based on-chip IOMMU
>>>>> driver which supports mapping the kernel dma buffer to a userspace iova
>>>>> region dynamically. The userspace iova region can be created by passing
>>>>> the userspace vDPA device fd to mmap(2).
>>>>>
>>>>> +In vhost-vdpa case, the dma buffer is reside in a userspace memory region
>>>>> +which will be shared to the VDUSE userspace processs via the file
>>>>> +descriptor in VDUSE_UPDATE_IOTLB message. And the corresponding address
>>>>> +mapping (IOVA of dma buffer <-> VA of the memory region) is also included
>>>>> +in this message.
>>>>> +
>>>>> Besides, the eventfd mechanism is used to trigger interrupt callbacks and
>>>>> receive virtqueue kicks in userspace. The following ioctls on the userspace
>>>>> vDPA device fd are provided to support that:
>>>>> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
>>>>> index b974333ed4e9..d24aaacb6008 100644
>>>>> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
>>>>> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
>>>>> @@ -34,6 +34,7 @@
>>>>>
>>>>> struct vduse_dev_msg {
>>>>> struct vduse_dev_request req;
>>>>> + struct file *iotlb_file;
>>>>> struct vduse_dev_response resp;
>>>>> struct list_head list;
>>>>> wait_queue_head_t waitq;
>>>>> @@ -325,12 +326,80 @@ static int vduse_dev_set_vq_state(struct vduse_dev *dev,
>>>>> return ret;
>>>>> }
>>>>>
>>>>> +static int vduse_dev_update_iotlb(struct vduse_dev *dev, struct file *file,
>>>>> + u64 offset, u64 iova, u64 size, u8 perm)
>>>>> +{
>>>>> + struct vduse_dev_msg *msg;
>>>>> + int ret;
>>>>> +
>>>>> + if (!size)
>>>>> + return -EINVAL;
>>>>> +
>>>>> + msg = vduse_dev_new_msg(dev, VDUSE_UPDATE_IOTLB);
>>>>> + msg->req.size = sizeof(struct vduse_iotlb);
>>>>> + msg->req.iotlb.offset = offset;
>>>>> + msg->req.iotlb.iova = iova;
>>>>> + msg->req.iotlb.size = size;
>>>>> + msg->req.iotlb.perm = perm;
>>>>> + msg->req.iotlb.fd = -1;
>>>>> + msg->iotlb_file = get_file(file);
>>>>> +
>>>>> + ret = vduse_dev_msg_sync(dev, msg);
>>>> My feeling is that we should provide consistent API for the userspace
>>>> device to use.
>>>>
>>>> E.g we'd better carry the IOTLB message for both virtio/vhost drivers.
>>>>
>>>> It looks to me for virtio drivers we can still use UPDAT_IOTLB message
>>>> by using VDUSE file as msg->iotlb_file here.
>>>>
>>> It's OK for me. One problem is when to transfer the UPDATE_IOTLB
>>> message in virtio cases.
>>
>> Instead of generating IOTLB messages for userspace.
>>
>> How about record the mappings (which is a common case for device have
>> on-chip IOMMU e.g mlx5e and vdpa simlator), then we can introduce ioctl
>> for userspace to query?
>>
> If so, the IOTLB UPDATE is actually triggered by ioctl, but
> IOTLB_INVALIDATE is triggered by the message. Is it a little odd?
Good point.
Some questions here:
1) Userspace think the IOTLB was flushed after IOTLB_INVALIDATE syscall
is returned. But this patch doesn't have this guarantee. Can this lead
some issues?
2) I think after VDUSE userspace receives IOTLB_INVALIDATE, it needs to
issue a munmap(). What if it doesn't do that?
> Or
> how about trigger it when userspace call mmap() on the device fd?
One possible issue is that the IOTLB_UPDATE/INVALIDATE might come after
mmap():
1) When vIOMMU is enabled
2) Guest memory topology has been changed (memory hotplug).
Thanks
>
> Thanks,
> Yongji
>
next prev parent reply other threads:[~2020-12-25 6:58 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-22 14:52 [RFC v2 00/13] Introduce VDUSE - vDPA Device in Userspace Xie Yongji
2020-12-22 14:52 ` [RFC v2 01/13] mm: export zap_page_range() for driver use Xie Yongji
2020-12-22 15:44 ` Christoph Hellwig
2020-12-22 14:52 ` [RFC v2 02/13] eventfd: track eventfd_signal() recursion depth separately in different cases Xie Yongji
2020-12-22 14:52 ` [RFC v2 03/13] eventfd: Increase the recursion depth of eventfd_signal() Xie Yongji
2020-12-22 14:52 ` [RFC v2 04/13] vdpa: Remove the restriction that only supports virtio-net devices Xie Yongji
2020-12-22 14:52 ` [RFC v2 05/13] vdpa: Pass the netlink attributes to ops.dev_add() Xie Yongji
2020-12-22 14:52 ` [RFC v2 06/13] vduse: Introduce VDUSE - vDPA Device in Userspace Xie Yongji
2020-12-23 8:08 ` Jason Wang
2020-12-23 14:17 ` Yongji Xie
2020-12-24 3:01 ` Jason Wang
2020-12-24 8:34 ` Yongji Xie
2020-12-25 6:59 ` Jason Wang
2021-01-08 13:32 ` Bob Liu
2021-01-10 10:03 ` Yongji Xie
2020-12-22 14:52 ` [RFC v2 07/13] vduse: support get/set virtqueue state Xie Yongji
2020-12-22 14:52 ` [RFC v2 08/13] vdpa: Introduce process_iotlb_msg() in vdpa_config_ops Xie Yongji
2020-12-23 8:36 ` Jason Wang
2020-12-23 11:06 ` Yongji Xie
2020-12-24 2:36 ` Jason Wang
2020-12-24 7:24 ` Yongji Xie
2020-12-22 14:52 ` [RFC v2 09/13] vduse: Add support for processing vhost iotlb message Xie Yongji
2020-12-23 9:05 ` Jason Wang
2020-12-23 12:14 ` [External] " Yongji Xie
2020-12-24 2:41 ` Jason Wang
2020-12-24 7:37 ` Yongji Xie
2020-12-25 2:37 ` Yongji Xie
2020-12-25 7:02 ` Jason Wang
2020-12-25 11:36 ` Yongji Xie
2020-12-25 6:57 ` Jason Wang [this message]
2020-12-25 10:31 ` Yongji Xie
2020-12-28 7:43 ` Jason Wang
2020-12-28 8:14 ` Yongji Xie
2020-12-28 8:43 ` Jason Wang
2020-12-28 9:12 ` Yongji Xie
2020-12-29 9:11 ` Jason Wang
2020-12-29 10:26 ` Yongji Xie
2020-12-30 6:10 ` Jason Wang
2020-12-30 7:09 ` Yongji Xie
2020-12-30 8:41 ` Jason Wang
2020-12-30 10:12 ` Yongji Xie
2020-12-31 2:49 ` Jason Wang
2020-12-31 5:15 ` Yongji Xie
2020-12-31 5:49 ` Jason Wang
2020-12-31 6:52 ` Yongji Xie
2020-12-31 7:11 ` Jason Wang
2020-12-31 8:00 ` Yongji Xie
2020-12-22 14:52 ` [RFC v2 10/13] vduse: grab the module's references until there is no vduse device Xie Yongji
2020-12-22 14:52 ` [RFC v2 11/13] vduse/iova_domain: Support reclaiming bounce pages Xie Yongji
2020-12-22 14:52 ` [RFC v2 12/13] vduse: Add memory shrinker to reclaim " Xie Yongji
2020-12-22 14:52 ` [RFC v2 13/13] vduse: Introduce a workqueue for irq injection Xie Yongji
2020-12-23 6:38 ` [RFC v2 00/13] Introduce VDUSE - vDPA Device in Userspace Jason Wang
2020-12-23 8:14 ` Jason Wang
2020-12-23 10:59 ` Yongji Xie
2020-12-24 2:24 ` Jason Wang
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