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Tsirkin" , Stefan Hajnoczi , sgarzare@redhat.com, Parav Pandit , akpm@linux-foundation.org, Randy Dunlap , Matthew Wilcox , 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 References: <20201222145221.711-1-xieyongji@bytedance.com> <20201222145221.711-10-xieyongji@bytedance.com> <6818a214-d587-4f0b-7de6-13c4e7e94ab6@redhat.com> <595fe7d6-7876-26e4-0b7c-1d63ca6d7a97@redhat.com> From: Jason Wang Message-ID: <0e6faf9c-117a-e23c-8d6d-488d0ec37412@redhat.com> Date: Fri, 25 Dec 2020 14:57:59 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2020/12/24 =E4=B8=8B=E5=8D=883:37, Yongji Xie wrote: > On Thu, Dec 24, 2020 at 10:41 AM Jason Wang wrote= : >> >> On 2020/12/23 =E4=B8=8B=E5=8D=888:14, Yongji Xie wrote: >>> On Wed, Dec 23, 2020 at 5:05 PM Jason Wang wrot= e: >>>> On 2020/12/22 =E4=B8=8B=E5=8D=8810:52, 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 proces= s. >>>>> >>>>> 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 >>>>> --- >>>>> 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/dri= ver-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 spa= ce >>>>> >>>>> +- 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 I= OMMU >>>>> +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-chi= p IOMMU >>>>> driver which supports mapping the kernel dma buffer to a usersp= ace 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 ad= dress >>>>> +mapping (IOVA of dma buffer <-> VA of the memory region) is also i= ncluded >>>>> +in this message. >>>>> + >>>>> Besides, the eventfd mechanism is used to trigger interrupt cal= lbacks and >>>>> receive virtqueue kicks in userspace. The following ioctls on t= he 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 vdus= e_dev *dev, >>>>> return ret; >>>>> } >>>>> >>>>> +static int vduse_dev_update_iotlb(struct vduse_dev *dev, struct fi= le *file, >>>>> + u64 offset, u64 iova, u64 size, u8 pe= rm) >>>>> +{ >>>>> + struct vduse_dev_msg *msg; >>>>> + int ret; >>>>> + >>>>> + if (!size) >>>>> + return -EINVAL; >>>>> + >>>>> + msg =3D vduse_dev_new_msg(dev, VDUSE_UPDATE_IOTLB); >>>>> + msg->req.size =3D sizeof(struct vduse_iotlb); >>>>> + msg->req.iotlb.offset =3D offset; >>>>> + msg->req.iotlb.iova =3D iova; >>>>> + msg->req.iotlb.size =3D size; >>>>> + msg->req.iotlb.perm =3D perm; >>>>> + msg->req.iotlb.fd =3D -1; >>>>> + msg->iotlb_file =3D get_file(file); >>>>> + >>>>> + ret =3D vduse_dev_msg_sync(dev, msg); >>>> My feeling is that we should provide consistent API for the userspac= e >>>> device to use. >>>> >>>> E.g we'd better carry the IOTLB message for both virtio/vhost driver= s. >>>> >>>> It looks to me for virtio drivers we can still use UPDAT_IOTLB messa= ge >>>> 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 ioct= l >> 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=20 is returned. But this patch doesn't have this guarantee. Can this lead=20 some issues? 2) I think after VDUSE userspace receives IOTLB_INVALIDATE, it needs to=20 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=20 mmap(): 1) When vIOMMU is enabled 2) Guest memory topology has been changed (memory hotplug). Thanks > > Thanks, > Yongji >