Virtualization Basics, VMware

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VirtualizationBasics, VMware KVM

• Lecturer Erez Melcer
• Course Advanced topics in OS
• Hebrew University in Jerusalem Israel

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Agenda

• Virtualization basics.
• CPU virtualization architectures.
• Memory virtualization architectures.
• VMware architecture products.
• VMware demo.
• KVM architecture products.
• KVM demo.
• Comparison KVM vs. VMware.
• Summary.

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Basics definition

• Wikipedia a technique for hiding the physical
  characteristics of computing resources from the
  way in which other systems, applications, or end
  users interact with those resources.
• In this presentationthe abstraction of
  physical resources in order to run multiple
  operating systems on the same underlying
  hardware

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Basics history

• Started in the 1960s IBM M44/44X.
• Abandoned in the 1980s and 1990s, due to
  cheiper x86 machines being the mainstream.
• VMware startedx86 virtualizationin 1999.

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Basics why virtualize?

• Consolidate Servers (less hardware, IT power)
• Run legacy software (that is not fit for new
  hardware)
• Sandbox un-trusted software.
• Multiple different OSes on same hardware
  simultaneously.
• Debug and performance monitoring.
• Fault containment (OS fault allows other OSes and
  their apps to continue)
• Migrating OSes (allows more up time)

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Basics acronyms

• PI privileged instruction.
• VM virtual machine.
• BT binary translation.

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CPU virtualization architectures

• Regular (non-virtualized) systemOS has full
  control over computer recourses and is free to
  issue PI.
• NoteUser-space alwaysruns directly on
  CPU.Only kernel has PIThat need to behandled
  differently invirtualized environment.

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CPU virtualization architectures

• Full virtualizationVirtualization layer uses BT
  to replace PI with instructions that have the
  same affect on the VM.
• Unmodified guest.
• Software overhead.

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CPU virtualization architectures

• Para-virtualizationGuest OS is modified to call
  functions insteadof issuing PI.
• Good performance
• Modified Kernel(Only Linux)(management
  overhead)

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CPU virtualization architectures

• Hardware assistCPU support of virtualization
  that eliminates the need for BT.
• Unmodified guest.
• Good performance(not yet).

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Memory virtualization architectures

• Hardware supports virtual to physical
  translation.
• For virtualization another layer is neededguest
  physical to host physical.
• This is done with shadow page tables, that hold
  guest virtual to host physical translation and
  are loaded to the hardware for direct translation.

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Memory virtualization architectures
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VMware
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VMware virtualization layer

• Full virtualization (first BT for x86).
• 2 architectures
• Hosted virtualization layer runs as an
  application on a hosting OS. supports more
  hardware.
• Hypervisor virtualization layer runs as the main
  OS (on bare wires). better performance.
• Virtualization layer manages the VMMs

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VMware VMM

• Virtual machine manager implements the
  abstraction of the hardware runs the guest OS
  on it.
• In charge of
• The binary translation of privileged
  instructions.
• Switching the MMU tables for 1 level translation
  of virtual memory.
• Connecting virtual I/O devices to real ones via
  routing multiplexing.

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VMware I/O virtualization

• software emulated devices rather than direct
  pass-through, in order to get a rich set of
  features
• Live migration.
• Software network switch.

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VMware desktop products

• VMware VDI Centralize PC in data centers.Saves
  costs on hardware and IT, while maintaining known
  look fell of the Desktop PC.
• VMware ACE Controlling virtual desktops.Allows
  IT to deploy, maintain control all desktop
  environments, from managed company-owned PCs to
  difficult to reach employee-owned.
• VMware Workstation Create and use virtual
  machines on a PC.Allows creation usage of
  virtual machines on the PC.

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VMware desktop products

• VMware Fusion Virtual machines for the
  Mac.Allows Mac OS to be the host OS. Also
  supports running Windows applications in the Mac
  environment.
• VMware Player Run virtual machines.Free, but
  allows only running of pre-created virtual
  machines.

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VMware server products

• VMware Infrastructure 3

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VMware server products

• VMware ESX Server VM-ware's Hypervisor.Runs as
  the host OS and is the base of Infrastructure 3.
• VMware ESX Server 3i A new hardware-integrated
  version of the ESX Server. It is only 32MB and
  has all the functionality.
• VMware Virtual SMP Runs virtual machines on up
  to 4 physical CPUs.
• VMware High Availability (HA) Keep virtualized
  apps running.Allows the automatic restart of
  virtual machines on different physical machines.
• VMware DRS Workload and power optimizing.Locates
  virtual machines on physical ones to optimize
  balance load and priorities. Low recourse
  requests cause virtual machine consolidation on
  physical ones and putting empty machines on
  stand-by.
• VMware VMotion Live migration of virtual
  machines.This is used in HA DRS.

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VMware server products

• VMware VMFS A cluster file system that
  leverages shared storage to allow multiple
  instances of ESX Server to read and write to the
  same storage, concurrently.
• VMware Server Free server version.Allows
  creation of virtual machines, but has less
  features than the Workstation.
• And more

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VMware demo
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KVM architecture

• Hardware assisted architecture.
• Linux Kernel as the Virtualization layer.
• Loadable Linux kernel modules.
• Supports Intel-VT AMD-V
• Only hosted, due to part of Linux.
• Main concept reuse of code
• Linux kernel abilities.
• QEMU project.

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KVM CPU virtualization

• Built in a triply-nested loop
• Modified QEMU process calls kernel to enter guest
  mode handles virtual motherboard.
• Kernel causes CPU to enter guest mode.Checks
  reason of exit. Interrupts and page faults are
  handles by kernel, I/O is forwarded to QEMU.
• CPU runs in guest mode until an instruction that
  needs assistance, a fault, or an external
  interrupt.

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KVM memory virtualization

• Works with shadow page tables that map guest
  virtual to host physical.
• First version trapped special TLB update
  instructions and did them on shadow page as well.
• Easy to implement.
• Bad performance, due to many context switches
  that flush the TLB. Shadow page rebuild is very
  expensive.

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KVM memory virtualization

• Enhanced version trapped memory writes to page
  tables by write-protecting the page tables.
• Harder to implement
• Write protecting memory regions.
• Reverse mapping of guest page tables.
• Parsing the caught x86 write instruction.
• Checking if pages are still used for page tables.
• Good performance, due to page table caching
  instead of rebuilding.

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KVM I/O virtualization

• I/O is forwarded to QEMU in user-space.There
  its fed into the motherboard model.
• Interrupts can be inserted from QEMU into the
  virtual machine.

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KVM demo

• KVM is currently run from Linux shell

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KVM demo
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KVM demo

• In Ubuntu 8.04 (Hardy Heron) KVM will be the
  supported virtualization package.
• It will use Red Hats Virtual Machine Manager
  GUI

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Comparison KVM vs. VMware.

• CPU virtualization
• VM-wareFull-virtualization solution, with use
  of para-virtualization drivers.
• KVMHardware assist solution, with
  para-virtualization drivers.
• My insightAs hardware assistance becomes more
  useful, it will be the major (and correct) way to
  implement virtualization.VM-ware is aware of
  this fact and is preparing for the age of
  hardware assist. It will be interesting to see
  how they keep ahead in this market when their
  major advantage, good binary translation, is not
  relevant.

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Comparison KVM vs. VMware.

• Memory virtualization Memory is virtualized
  very similarly in both KVM and VM-ware.This is
  the major overhead in virtualization and will be
  improved in nested TLB support in feature CPUs.

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Comparison KVM vs. VMware.

• I/O virtualizationAlso I/O virtualization is
  similar in both VM-ware and KVM.It is forwarded
  to user-space, QEMU in KVM and VM-ware user-space
  layer in VM-ware. This allows both of them to
  support advanced features in software, such as
  live migration.

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Comparison KVM vs. VMware.

• Cost
• VM-Ware
• VM-ware gives basic virtualization solutions for
  free.
• VM-ware Workstation costs about 190.
• VM-ware ESX server costs about 500 for the basic
  suite and up to 5,750 for the full enterprise
  suite.
• KVMKVM is an open-source project under the GPL
  license, so it is free to use and improve.KVM
  offers today features that are in VM-ware's
  enterprise suite for free, such as live
  migration.
• My insightIf KVM continues on its course, gains
  more community support, and hardware support is
  improved than their product will be very
  appealing and will win a major segment share in
  the low to middle market.VM-ware will keep its
  lead in the high end market due to being far
  ahead (though they rely on binary translation
  that will soon be obsolete).

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Comparison KVM vs. VMware.

• Patriotism
• VM-ware is an American company.
• KVM is funded by Qumranet that has offices in
  Raanana and California. It is managed by Avi
  Kivity.

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Summary

• VM-ware were first to market and have a major
  lead on everyone else. They have a fuller more
  mature product line and support. For this reason
  hardware vendors work with them and they might
  have a look ahead on next generation hardware
  support before KVM.
• KVM is an open-source project that re-uses the
  Linux Kernel feature for virtualization. This
  re-use gives them continuous updates and
  improvements just from gaining the Kernel
  scheduling and memory handling updates. As
  open-source solutions gain more use and support
  all the time, and Ubuntu has chosen them as their
  virtualization solution, they are a rising power
  in the virtualization world.