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KVM on S390x. Revolutionizing the Mainframe. About Me. Alexander Graf SUSE Studio team KVM and Qemu developer Server class PowerPC KVM port S390x Qemu guest support x86 Mac OS X in KVM. Audience. In depth technology High level overview. Yes, you get both!. S390x?. Mainframe
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KVM on S390x • Revolutionizing the Mainframe
About Me • Alexander Graf • SUSE Studio team • KVM and Qemu developer • Server class PowerPC KVM port • S390x Qemu guest support • x86 Mac OS X in KVM • ...
Audience • In depth technology • High level overview Yes, you get both!
S390x? • Mainframe • Highly available • Highly compatible • 64 Bit • Introduced in 2000 • Marketing term: System z
Hypervisor? VM VM Application Application Application Application Linux Linux Hypervisor Hardware
Virtualization History x86 Xen 8086 KVM S/360 KVM S/360 VM/370 370/XA z/VM 1965 1972 1981 2000 2008 1978 2003 2007
z/VM • Virtualization method of choice on S390x • Emulates real S390x hardware • Can run classic Operating Systems
z/VM Architecture VM VM VM Application Application Application Application Linux z/OS Linux z/VM
z/VM • Made for Mainframe OSs • Not integrated into Linux • More advanced than most other hypervisors
What is KVM? • Kernel module • Creates virtual machine contexts • Requires userspace application for device emulation • Commonly KVM & Qemu are referred to as “KVM”
KVM History RHEL6 SLES11 SP1 VT-x KVM S390x KVM x86 Qemu S390x 2006 2008 2010
KVM Architecture VM VM Application Application Application Linux Linux SLES Qemu Qemu Application Linux KVM
KVM UI • Direct console mode • VNC • SDL • Currently text output only
KVM UI • Considers itself a backend • Users only see management software
Virtio • Paravirtual devices • Originated in Lguest • Network and block devices of choice for KVM
Shared Code Virtio Virtio-Block Virtio-Net Virtio-Serial Device Virtio-Ring Ring Virtio-PCI Virtio-S390 Backend
Virtio on S390x • Only emulated bus type on S390x • Virtio-Serial used for console • No performance penalties from imitating real hardware • Uses queue based transport similar to Qdio
S390 Virtio Bus RAM Device Info Ring1 Ring2 Ring3 Ring... Device Info Device 1 Device 2 Device ...
S390 Virtio Bus RAM Device Info Ring1 Ring2 Ring3 Ring... Ring Processing Done
S390 Virtio Bus Hypervisor Virtual Machine Interrupt Ring Hypercall
S390 Virtio Bus • Very simple • Limited space for device descriptors • Device overhead above RAM limit
S390 Virtio Machine • Fully paravirtual machine • Uses • virtio-serial for console • virtio-block for block • virtio-net for network • virtio-rng for random number generation • Linux only
Why? • Easy to use • Flexible • Linux way of doing things • Big ecosystem
libguestfs • Seamless access of VM images • Spawns KVM internally
KVM vs z/VM • Linux only • Tightly integrated • Opens up new possibilities • Easier to use • KSM
KVM vs z/VM • Lacking features • Very fast development • Room for coexistence!