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Subject: Re: [virtio-dev] [PATCH 0/2] introduce virtio-ism: internal shared memory device
On Wed, 19 Oct 2022 17:11:21 +0800, Jason Wang <jasowang@redhat.com> wrote: > On Wed, Oct 19, 2022 at 4:19 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote: > > > > On Wed, 19 Oct 2022 16:13:07 +0800, Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote: > > > 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. > > > > For example, if the hardware memory of a virtio-ism is 1G, and an ism region is > > 1M, there are 1000 ism regions, and these ism regions can be shared with > > different vms. > > Right, this is what I've understood. > > What I want to say this might be achieved with virtio-vhost-user as > well. But it may require a some changes on the protocol which I'm not > sure it's worth to bother. And I've started to think about the > possibility to build virtio-vhost-user on top (I don't see any blocker > so far). Yes, it is theoretically possible to implement based on virtio-vhost-user. But when we try to implement it without depending on virtio-vhost-user, this implementation is also very simple. Because the physical memory it shares does not come from a vm, but from the host. So I think we have reached an agreement on the relationship between ism and virtio-vhost-user. ism is used to provide shared memory to the upper layer, and this device should be necessary to add (of course, listen to some other people's opinions). And How is its backend shared with other vms? This is our second question. Thanks. > > Thanks > > > > > And it is dynamic. After an ism region is shared with a vm, it can be shared > > with other vms. > > > > Thanks. > > > > > > > > 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 > > > > > > > > > > > > > > > > > > > > > > > > > > > > --------------------------------------------------------------------- > > > 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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