KVM & libvirt interview questions

1. A.A paravirtualized device standard for KVM/QEMU giving guests efficient virtio-net, virtio-blk and virtio-scsi drivers instead of slow emulated hardware
2. B.Allocating guest memory from host huge pages to cut TLB misses, commonly required for DPDK and high-performance KVM workloads
3. C.Copy-on-write QEMU disk format supporting snapshots, thin provisioning, compression, and backing files.
4. D.A userspace dataplane interface that connects virtio devices to an external process such as a DPDK/OVS poll-mode driver for line-rate networking

Answer + AI explanation with Pro

1. A.virtio
2. B.cloud-init
3. C.Linux bridge networking
4. D.vhost-net

Answer + AI explanation with Pro

1. A.virtio — Allocating guest memory from host huge pages to cut TLB misses, commonly required for DPDK and high-performance KVM workloads
2. B.virtio — A guest-side tool that configures a freshly booted cloud image (hostname, SSH keys, network, packages) from metadata supplied by the platform
3. C.virtio — A shared-filesystem device that lets a guest directly access a directory on the host with near-native performance, used heavily by KubeVirt and Kata
4. D.virtio — A paravirtualized device standard for KVM/QEMU giving guests efficient virtio-net, virtio-blk and virtio-scsi drivers instead of slow emulated hardware

Answer + AI explanation with Pro

1. A.A Linux framework that carves a physical device, typically a GPU, into virtual instances passed through to VMs, the basis of NVIDIA vGPU on KVM
2. B.Allocating guest memory from host huge pages to cut TLB misses, commonly required for DPDK and high-performance KVM workloads
3. C.Assigns a host PCI device (GPU, NIC) directly to a guest via the vfio-pci driver and IOMMU groups.
4. D.A shared-filesystem device that lets a guest directly access a directory on the host with near-native performance, used heavily by KubeVirt and Kata

Answer + AI explanation with Pro

1. A.Linux bridge networking
2. B.huge pages backing
3. C.virtio-fs
4. D.libvirt domain XML

Answer + AI explanation with Pro

1. A.virtio-fs — A shared-filesystem device that lets a guest directly access a directory on the host with near-native performance, used heavily by KubeVirt and Kata
2. B.virtio-fs — A guest-side tool that configures a freshly booted cloud image (hostname, SSH keys, network, packages) from metadata supplied by the platform
3. C.virtio-fs — The declarative XML definition of a VM (CPU, memory, disks, NICs) that libvirt uses to create and manage the guest across hypervisors
4. D.virtio-fs — Multilayer virtual switch giving KVM guests VLANs, tunneling, and OpenFlow-controlled networking.

Answer + AI explanation with Pro

1. A.AMD Secure Encrypted Virtualization-Secure Nested Paging: encrypts and integrity-protects a VM's memory from the hypervisor, enabling confidential VMs on KVM
2. B.A shared-filesystem device that lets a guest directly access a directory on the host with near-native performance, used heavily by KubeVirt and Kata
3. C.A kernel module that moves virtio-net packet processing into the host kernel, bypassing the QEMU userspace data path for higher network throughput
4. D.Copy-on-write QEMU disk format supporting snapshots, thin provisioning, compression, and backing files.

Answer + AI explanation with Pro

1. A.vhost-net
2. B.mediated device (mdev)
3. C.huge pages backing
4. D.Hugepages backing

Answer + AI explanation with Pro

1. A.vhost-net — Assigns a host PCI device (GPU, NIC) directly to a guest via the vfio-pci driver and IOMMU groups.
2. B.vhost-net — Paravirtualized device model (net, blk, scsi) giving near-native I/O performance to KVM guests.
3. C.vhost-net — A kernel module that moves virtio-net packet processing into the host kernel, bypassing the QEMU userspace data path for higher network throughput
4. D.vhost-net — A Linux framework that carves a physical device, typically a GPU, into virtual instances passed through to VMs, the basis of NVIDIA vGPU on KVM

Answer + AI explanation with Pro

1. A.A userspace dataplane interface that connects virtio devices to an external process such as a DPDK/OVS poll-mode driver for line-rate networking
2. B.libvirt XML element that pins guest memory to specific host NUMA nodes for bandwidth-sensitive workloads.
3. C.virtio-scsi supports more disks, TRIM/discard, and SCSI passthrough; virtio-blk is simpler and slightly faster.
4. D.Multilayer virtual switch giving KVM guests VLANs, tunneling, and OpenFlow-controlled networking.

Answer + AI explanation with Pro

1. A.cloud-init
2. B.Open vSwitch integration
3. C.PCI passthrough (VFIO)
4. D.vhost-user

Answer + AI explanation with Pro

1. A.vhost-user — Copy-on-write QEMU disk format supporting snapshots, thin provisioning, compression, and backing files.
2. B.vhost-user — A userspace dataplane interface that connects virtio devices to an external process such as a DPDK/OVS poll-mode driver for line-rate networking
3. C.vhost-user — Paravirtualized device model (net, blk, scsi) giving near-native I/O performance to KVM guests.
4. D.vhost-user — Assigns a host PCI device (GPU, NIC) directly to a guest via the vfio-pci driver and IOMMU groups.

Answer + AI explanation with Pro

1. A.A shared-filesystem device that lets a guest directly access a directory on the host with near-native performance, used heavily by KubeVirt and Kata
2. B.Backs guest RAM with 2MB or 1GB pages to cut TLB misses and reduce page-table overhead.
3. C.A guest-side tool that configures a freshly booted cloud image (hostname, SSH keys, network, packages) from metadata supplied by the platform
4. D.libvirt XML element that pins guest memory to specific host NUMA nodes for bandwidth-sensitive workloads.

Answer + AI explanation with Pro

1. A.cloud-init
2. B.vhost-net
3. C.virtio
4. D.Open vSwitch integration

Answer + AI explanation with Pro

1. A.cloud-init — A copy-on-write base image referenced by a thin overlay qcow2, so many VMs share one read-only base while writing private deltas
2. B.cloud-init — A guest-side tool that configures a freshly booted cloud image (hostname, SSH keys, network, packages) from metadata supplied by the platform
3. C.cloud-init — Software bridge (br0) connecting guest tap interfaces to a physical NIC for direct L2 access.
4. D.cloud-init — virtio-scsi supports more disks, TRIM/discard, and SCSI passthrough; virtio-blk is simpler and slightly faster.

Answer + AI explanation with Pro

1. A.Backs guest RAM with 2MB or 1GB pages to cut TLB misses and reduce page-table overhead.
2. B.A kernel module that moves virtio-net packet processing into the host kernel, bypassing the QEMU userspace data path for higher network throughput
3. C.Software bridge (br0) connecting guest tap interfaces to a physical NIC for direct L2 access.
4. D.A Linux framework that carves a physical device, typically a GPU, into virtual instances passed through to VMs, the basis of NVIDIA vGPU on KVM

Answer + AI explanation with Pro

1. A.vhost-user
2. B.PCI passthrough (VFIO)
3. C.mediated device (mdev)
4. D.NUMA tuning (numatune)

Answer + AI explanation with Pro

1. A.mediated device (mdev) — Paravirtualized device model (net, blk, scsi) giving near-native I/O performance to KVM guests.
2. B.mediated device (mdev) — Software bridge (br0) connecting guest tap interfaces to a physical NIC for direct L2 access.
3. C.mediated device (mdev) — A Linux framework that carves a physical device, typically a GPU, into virtual instances passed through to VMs, the basis of NVIDIA vGPU on KVM
4. D.mediated device (mdev) — A userspace dataplane interface that connects virtio devices to an external process such as a DPDK/OVS poll-mode driver for line-rate networking

Answer + AI explanation with Pro

1. A.A guest-side tool that configures a freshly booted cloud image (hostname, SSH keys, network, packages) from metadata supplied by the platform
2. B.Allocating guest memory from host huge pages to cut TLB misses, commonly required for DPDK and high-performance KVM workloads
3. C.Paravirtualized device model (net, blk, scsi) giving near-native I/O performance to KVM guests.
4. D.AMD Secure Encrypted Virtualization-Secure Nested Paging: encrypts and integrity-protects a VM's memory from the hypervisor, enabling confidential VMs on KVM

Answer + AI explanation with Pro

1. A.qcow2 backing file
2. B.virtio drivers
3. C.SEV-SNP
4. D.virtio-scsi vs virtio-blk

Answer + AI explanation with Pro

1. A.SEV-SNP — The declarative XML definition of a VM (CPU, memory, disks, NICs) that libvirt uses to create and manage the guest across hypervisors
2. B.SEV-SNP — A shared-filesystem device that lets a guest directly access a directory on the host with near-native performance, used heavily by KubeVirt and Kata
3. C.SEV-SNP — Multilayer virtual switch giving KVM guests VLANs, tunneling, and OpenFlow-controlled networking.
4. D.SEV-SNP — AMD Secure Encrypted Virtualization-Secure Nested Paging: encrypts and integrity-protects a VM's memory from the hypervisor, enabling confidential VMs on KVM

Answer + AI explanation with Pro

1. A.A guest-side tool that configures a freshly booted cloud image (hostname, SSH keys, network, packages) from metadata supplied by the platform
2. B.A copy-on-write base image referenced by a thin overlay qcow2, so many VMs share one read-only base while writing private deltas
3. C.The declarative XML definition of a VM (CPU, memory, disks, NICs) that libvirt uses to create and manage the guest across hypervisors
4. D.Paravirtualized device model (net, blk, scsi) giving near-native I/O performance to KVM guests.

Answer + AI explanation with Pro

1. A.cloud-init
2. B.qcow2 format
3. C.Linux bridge networking
4. D.libvirt domain XML

Answer + AI explanation with Pro

1. A.libvirt domain XML — A kernel module that moves virtio-net packet processing into the host kernel, bypassing the QEMU userspace data path for higher network throughput
2. B.libvirt domain XML — The declarative XML definition of a VM (CPU, memory, disks, NICs) that libvirt uses to create and manage the guest across hypervisors
3. C.libvirt domain XML — Multilayer virtual switch giving KVM guests VLANs, tunneling, and OpenFlow-controlled networking.
4. D.libvirt domain XML — Paravirtualized device model (net, blk, scsi) giving near-native I/O performance to KVM guests.

Answer + AI explanation with Pro

1. A.A Linux framework that carves a physical device, typically a GPU, into virtual instances passed through to VMs, the basis of NVIDIA vGPU on KVM
2. B.libvirt XML element that pins guest memory to specific host NUMA nodes for bandwidth-sensitive workloads.
3. C.Software bridge (br0) connecting guest tap interfaces to a physical NIC for direct L2 access.
4. D.A copy-on-write base image referenced by a thin overlay qcow2, so many VMs share one read-only base while writing private deltas

Answer + AI explanation with Pro

1. A.virtio drivers
2. B.Hugepages backing
3. C.qcow2 backing file
4. D.Open vSwitch integration

Answer + AI explanation with Pro

1. A.qcow2 backing file — A userspace dataplane interface that connects virtio devices to an external process such as a DPDK/OVS poll-mode driver for line-rate networking
2. B.qcow2 backing file — The declarative XML definition of a VM (CPU, memory, disks, NICs) that libvirt uses to create and manage the guest across hypervisors
3. C.qcow2 backing file — A guest-side tool that configures a freshly booted cloud image (hostname, SSH keys, network, packages) from metadata supplied by the platform
4. D.qcow2 backing file — A copy-on-write base image referenced by a thin overlay qcow2, so many VMs share one read-only base while writing private deltas

Answer + AI explanation with Pro

1. A.A paravirtualized device standard for KVM/QEMU giving guests efficient virtio-net, virtio-blk and virtio-scsi drivers instead of slow emulated hardware
2. B.The declarative XML definition of a VM (CPU, memory, disks, NICs) that libvirt uses to create and manage the guest across hypervisors
3. C.virtio-scsi supports more disks, TRIM/discard, and SCSI passthrough; virtio-blk is simpler and slightly faster.
4. D.Allocating guest memory from host huge pages to cut TLB misses, commonly required for DPDK and high-performance KVM workloads

Answer + AI explanation with Pro

1. A.cloud-init
2. B.qcow2 format
3. C.huge pages backing
4. D.Hugepages backing

Answer + AI explanation with Pro

1. A.huge pages backing — A userspace dataplane interface that connects virtio devices to an external process such as a DPDK/OVS poll-mode driver for line-rate networking
2. B.huge pages backing — Allocating guest memory from host huge pages to cut TLB misses, commonly required for DPDK and high-performance KVM workloads
3. C.huge pages backing — Software bridge (br0) connecting guest tap interfaces to a physical NIC for direct L2 access.
4. D.huge pages backing — A kernel module that moves virtio-net packet processing into the host kernel, bypassing the QEMU userspace data path for higher network throughput

Answer + AI explanation with Pro