On Mon, Jan 15, 2024 at 5:33 PM Stefan Hajnoczi <stefanha@xxxxxxxxx> wrote: > > Dear QEMU and KVM communities, > QEMU will apply for the Google Summer of Code and Outreachy internship > programs again this year. Regular contributors can submit project > ideas that they'd like to mentor by replying to this email before > January 30th. > === Add packed virtqueue to Shadow Virtqueue === Summary: Add the packed virtqueue format support to QEMU's Shadow Virtqueue. To perform a virtual machine live migration with an external device to qemu, qemu needs a way to know which memory the device modifies so it is able to resend it. Otherwise the guest would resume with invalid / outdated memory in the destination. This is especially hard with passthrough hardware devices, as transports like PCI imposes a few security and performance challenges. As a method to overcome this for virtio devices, qemu can offer an emulated virtqueue to the device, called Shadow Virtqueue (SVQ), instead of allowing the device to communicate directly with the guest. SVQ will then forward the writes to the guest, being the effective writer in the guest memory and knowing when a portion of it needs to be resent. Compared with original Split Virtqueues, already supported by Shadow Virtqueue, Packed virtqueue is a more compact representation that uses less memory size and allows both devices and drivers to exchange the same amount of information with less memory operations. The task is to complete the packed virtqueue support for SVQ, using the kernel virtio ring driver as a reference. There is already a setup that can be used to test the changes. Links: * https://www.redhat.com/en/blog/virtio-devices-and-drivers-overview-headjack-and-phone * https://www.redhat.com/en/blog/virtqueues-and-virtio-ring-how-data-travels * https://www.redhat.com/en/blog/packed-virtqueue-how-reduce-overhead-virtio * https://www.youtube.com/watch?v=x9ARoNVzS04 Details: * Skill level: Intermediate * Language: C
