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Subject: Re: [virtio-dev] [PATCH 0/2] introduce virtio-ism: internal shared memory device
On Wed, 19 Oct 2022 16:01:42 +0800, Jason Wang <jasowang@redhat.com> wrote: > On Wed, Oct 19, 2022 at 3:00 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote: > > > > On Tue, 18 Oct 2022 14:54:22 +0800, Jason Wang <jasowang@redhat.com> wrote: > > > On Mon, Oct 17, 2022 at 8:31 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote: > > > > > > > > On Mon, 17 Oct 2022 16:17:31 +0800, Jason Wang <jasowang@redhat.com> wrote: > > > > > Adding Stefan. > > > > > > > > > > > > > > > On Mon, Oct 17, 2022 at 3:47 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote: > > > > > > > > > > > > Hello everyone, > > > > > > > > > > > > # Background > > > > > > > > > > > > Nowadays, there is a common scenario to accelerate communication between > > > > > > different VMs and containers, including light weight virtual machine based > > > > > > containers. One way to achieve this is to colocate them on the same host. > > > > > > However, the performance of inter-VM communication through network stack is not > > > > > > optimal and may also waste extra CPU cycles. This scenario has been discussed > > > > > > many times, but still no generic solution available [1] [2] [3]. > > > > > > > > > > > > With pci-ivshmem + SMC(Shared Memory Communications: [4]) based PoC[5], > > > > > > We found that by changing the communication channel between VMs from TCP to SMC > > > > > > with shared memory, we can achieve superior performance for a common > > > > > > socket-based application[5]: > > > > > > - latency reduced by about 50% > > > > > > - throughput increased by about 300% > > > > > > - CPU consumption reduced by about 50% > > > > > > > > > > > > Since there is no particularly suitable shared memory management solution > > > > > > matches the need for SMC(See ## Comparison with existing technology), and virtio > > > > > > is the standard for communication in the virtualization world, we want to > > > > > > implement a virtio-ism device based on virtio, which can support on-demand > > > > > > memory sharing across VMs, containers or VM-container. To match the needs of SMC, > > > > > > the virtio-ism device need to support: > > > > > > > > > > > > 1. Dynamic provision: shared memory regions are dynamically allocated and > > > > > > provisioned. > > > > > > 2. Multi-region management: the shared memory is divided into regions, > > > > > > and a peer may allocate one or more regions from the same shared memory > > > > > > device. > > > > > > 3. Permission control: The permission of each region can be set seperately. > > > > > > > > > > Looks like virtio-ROCE > > > > > > > > > > https://lore.kernel.org/all/20220511095900.343-1-xieyongji@bytedance.com/T/ > > > > > > > > > > and virtio-vhost-user can satisfy the requirement? > > > > > > > > > > > > > > > > > # Virtio ism device > > > > > > > > > > > > ISM devices provide the ability to share memory between different guests on a > > > > > > host. A guest's memory got from ism device can be shared with multiple peers at > > > > > > the same time. This shared relationship can be dynamically created and released. > > > > > > > > > > > > The shared memory obtained from the device is divided into multiple ism regions > > > > > > for share. ISM device provides a mechanism to notify other ism region referrers > > > > > > of content update events. > > > > > > > > > > > > # Usage (SMC as example) > > > > > > > > > > > > Maybe there is one of possible use cases: > > > > > > > > > > > > 1. SMC calls the interface ism_alloc_region() of the ism driver to return the > > > > > > location of a memory region in the PCI space and a token. > > > > > > 2. The ism driver mmap the memory region and return to SMC with the token > > > > > > 3. SMC passes the token to the connected peer > > > > > > 3. the peer calls the ism driver interface ism_attach_region(token) to > > > > > > get the location of the PCI space of the shared memory > > > > > > > > > > > > > > > > > > # About hot plugging of the ism device > > > > > > > > > > > > Hot plugging of devices is a heavier, possibly failed, time-consuming, and > > > > > > less scalable operation. So, we don't plan to support it for now. > > > > > > > > > > > > # Comparison with existing technology > > > > > > > > > > > > ## ivshmem or ivshmem 2.0 of Qemu > > > > > > > > > > > > 1. ivshmem 1.0 is a large piece of memory that can be seen by all devices that > > > > > > use this VM, so the security is not enough. > > > > > > > > > > > > 2. ivshmem 2.0 is a shared memory belonging to a VM that can be read-only by all > > > > > > other VMs that use the ivshmem 2.0 shared memory device, which also does not > > > > > > meet our needs in terms of security. > > > > > > > > > > > > ## vhost-pci and virtiovhostuser > > > > > > > > > > > > Does not support dynamic allocation and therefore not suitable for SMC. > > > > > > > > > > I think this is an implementation issue, we can support VHOST IOTLB > > > > > message then the regions could be added/removed on demand. > > > > > > > > > > > > 1. After the attacker connects with the victim, if the attacker does not > > > > dereference memory, the memory will be occupied under virtiovhostuser. In the > > > > case of ism devices, the victim can directly release the reference, and the > > > > maliciously referenced region only occupies the attacker's resources > > > > > > Let's define the security boundary here. E.g do we trust the device or > > > not? If yes, in the case of virtiovhostuser, can we simple do > > > VHOST_IOTLB_UNMAP then we can safely release the memory from the > > > attacker. > > > > > > > > > > > 2. The ism device of a VM can be shared with multiple (1000+) VMs at the same > > > > time, which is a challenge for virtiovhostuser > > > > > > Please elaborate more the the challenges, anything make > > > virtiovhostuser different? > > > > I understand (please point out any mistakes), one vvu device corresponds to one > > vm. If we share memory with 1000 vm, do we have 1000 vvu devices? > > There could be some misunderstanding here. With 1000 VM, you still > need 1000 virtio-sim devices I think. No, just use a virtio-ism device. Thanks. > > > > > > > > > > > > > > > > 3. The sharing relationship of ism is dynamically increased, and virtiovhostuser > > > > determines the sharing relationship at startup. > > > > > > Not necessarily with IOTLB API? > > > > Unlike virtio-vhost-user, which shares the memory of a vm with another vm, we > > provide the same memory on the host to two vms. So the implementation of this > > part will be much simpler. This is why we gave up virtio-vhost-user at the > > beginning. > > Ok, just to make sure we're at the same page. From spec level, > virtio-vhost-user doesn't (can't) limit the backend to be implemented > in another VM. So it should be ok to be used for sharing memory > between a guest and host. > > Thanks > > > > > Thanks. > > > > > > > > > > > > > > > 4. For security issues, the device under virtiovhostuser may mmap more memory, > > > > while ism only maps one region to other devices > > > > > > With VHOST_IOTLB_MAP, the map could be done per region. > > > > > > Thanks > > > > > > > > > > > Thanks. > > > > > > > > > > > > > > Thanks > > > > > > > > > > > > > > > > > # Design > > > > > > > > > > > > This is a structure diagram based on ism sharing between two vms. > > > > > > > > > > > > |-------------------------------------------------------------------------------------------------------------| > > > > > > | |------------------------------------------------| |------------------------------------------------| | > > > > > > | | Guest | | Guest | | > > > > > > | | | | | | > > > > > > | | ---------------- | | ---------------- | | > > > > > > | | | driver | [M1] [M2] [M3] | | | driver | [M2] [M3] | | > > > > > > | | ---------------- | | | | | ---------------- | | | | > > > > > > | | |cq| |map |map |map | | |cq| |map |map | | > > > > > > | | | | | | | | | | | | | | | > > > > > > | | | | ------------------- | | | | -------------------- | | > > > > > > | |----|--|----------------| device memory |-----| |----|--|----------------| device memory |----| | > > > > > > | | | | ------------------- | | | | -------------------- | | > > > > > > | | | | | | | | > > > > > > | | | | | | | | > > > > > > | | Qemu | | | Qemu | | | > > > > > > | |--------------------------------+---------------| |-------------------------------+----------------| | > > > > > > | | | | > > > > > > | | | | > > > > > > | |------------------------------+------------------------| | > > > > > > | | | > > > > > > | | | > > > > > > | -------------------------- | > > > > > > | | M1 | | M2 | | M3 | | > > > > > > | -------------------------- | > > > > > > | | > > > > > > | HOST | > > > > > > --------------------------------------------------------------------------------------------------------------- > > > > > > > > > > > > # POC code > > > > > > > > > > > > Kernel: https://github.com/fengidri/linux-kernel-virtio-ism/commits/ism > > > > > > Qemu: https://github.com/fengidri/qemu/commits/ism > > > > > > > > > > > > If there are any problems, please point them out. > > > > > > > > > > > > Hope to hear from you, thank you. > > > > > > > > > > > > [1] https://projectacrn.github.io/latest/tutorials/enable_ivshmem.html > > > > > > [2] https://dl.acm.org/doi/10.1145/2847562 > > > > > > [3] https://hal.archives-ouvertes.fr/hal-00368622/document > > > > > > [4] https://lwn.net/Articles/711071/ > > > > > > [5] https://lore.kernel.org/netdev/20220720170048.20806-1-tonylu@linux.alibaba.com/T/ > > > > > > > > > > > > > > > > > > Xuan Zhuo (2): > > > > > > Reserve device id for ISM device > > > > > > virtio-ism: introduce new device virtio-ism > > > > > > > > > > > > content.tex | 3 + > > > > > > virtio-ism.tex | 340 +++++++++++++++++++++++++++++++++++++++++++++++++ > > > > > > 2 files changed, 343 insertions(+) > > > > > > create mode 100644 virtio-ism.tex > > > > > > > > > > > > -- > > > > > > 2.32.0.3.g01195cf9f > > > > > > > > > > > > > > > > > > --------------------------------------------------------------------- > > > > > > To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org > > > > > > For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org > > > > > > > > > > > > > > > > > > > --------------------------------------------------------------------- > > > > To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org > > > > For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org > > > > > > > > > >
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