Hypervisors
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Hypervisors are a kind of software which runs different virtual systems called virtual machines on a single computer giving the view to guest running on each virtual machine that it is running on its own single computer. This presentation talks about hypervisors and different techniques of their implementation in brief.
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Hypervisors
- 2. Motivation • In some situations, organizations need different computers but actually do not want it.
- 3. Motivation • In some situations, organizations need different computers but actually do not want it. • E.g. a company has e-mail server, web server, FTP server, etc.
- 4. Motivation • In some situations, organizations need different computers but actually do not want it. • E.g. a company has e-mail server, web server, FTP server, etc. • Due to reliability, use separate machines
- 5. Motivation • In some situations, organizations need different computers but actually do not want it. • E.g. a company has e-mail server, web server, FTP server, etc. • Due to reliability, use separate machines Solution is virtualization
- 6. Virtualization • Allows a single computer to run different virtual systems (Virtual Machines).
- 7. Virtualization • Allows a single computer to run different virtual systems (Virtual Machines). • Abstracts the hardware of a single computer into different execution environments
- 8. Virtualization • Allows a single computer to run different virtual systems (Virtual Machines). • Abstracts the hardware of a single computer into different execution environments • Creates illusion that each execution environment is running on its own private computer
- 9. Virtualization • Allows a single computer to run different virtual systems (Virtual Machines). • Abstracts the hardware of a single computer into different execution environments • Creates illusion that each execution environment is running on its own private computer • Failure in one virtual machine do not affect other virtual machines
- 10. Types of Hypervisors • Type 1 hypervisor
- 11. Types of Hypervisors • Type 1 hypervisor Type 1 Hypervisor Hardware Windows Linux
- 12. Types of Hypervisors • Type 1 hypervisor • Type 2 hypervisor Type 1 Hypervisor Hardware Windows Linux
- 13. Types of Hypervisors • Type 1 hypervisor • Type 2 hypervisor Type 1 Hypervisor Hardware Windows Linux Type 2 Hypervisor Hardware Guest OS Host Operating System Other OS processes Type 1 Hypervisor Type 2 Hypervisor
- 14. Requirements for Virtualization • CPU has some instructions which can only be executed in kernel mode e.g. perform I/O, changing MMU settings, etc.
- 15. Requirements for Virtualization • CPU has some instructions which can only be executed in kernel mode e.g. perform I/O, changing MMU settings, etc. • These instructions are called sensitive instructions
- 16. Requirements for Virtualization • CPU has some instructions which can only be executed in kernel mode e.g. perform I/O, changing MMU settings, etc. • These instructions are called sensitive instructions • Some instructions cause a trap if executed in user mode
- 17. Requirements for Virtualization • CPU has some instructions which can only be executed in kernel mode e.g. perform I/O, changing MMU settings, etc. • These instructions are called sensitive instructions • Some instructions cause a trap if executed in user mode • These instructions are called privileged instructions
- 18. Requirements for Virtualization • CPU has some instructions which can only be executed in kernel mode e.g. perform I/O, changing MMU settings, etc. • These instructions are called sensitive instructions • Some instructions cause a trap if executed in user mode • These instructions are called privileged instructions • A machine is virtualizable if sensitive instructions are subset of privileged instructions. Popek and Goldberg, Formal Requirements for Virtualizable Third Generation Architectures, Commun. Of ACM, 1974
- 19. Different Techniques of Implementation • Binary translation • Paravirtualization • Hardware support
- 20. Binary Translation …. …. Sensitive instruction …. …. Basic Block in code of guest OS
- 21. Binary Translation …. …. Sensitive instruction …. …. Basic Block in code of guest OS …. …. VMware procedure …. ….
- 22. Paravirtualization • Modifies guest OS source code, and directly executes hypervisor calls
- 23. Hardware Support – Bird’s-eye View • In 2006, Intel introduced VT-x Hardware OS User Applications VMM
- 24. Hardware Support – Bird’s-eye View • In 2006, Intel introduced VT-x Hardware OS User Applications VMM VMX Root Mode VMX Non-Root Mode
- 25. VT-x Operating Modes • Set of processor operations called VMX operations
- 26. VT-x Operating Modes • Set of processor operations called VMX operations • Two kinds of VMX operation
- 27. VT-x Operating Modes • Set of processor operations called VMX operations • Two kinds of VMX operation • VMX root operation • Fully privileged, generally for VMM
- 28. VT-x Operating Modes • Set of processor operations called VMX operations • Two kinds of VMX operation • VMX root operation • Fully privileged, generally for VMM • VMX non-root operation • Not fully privileged, generally for guest • Reduces the privilege of guest software developed to operate in ring 0
- 29. VM Entry and Exit • Two types of transitions
- 30. VM Entry and Exit • Two types of transitions • VM entry • Transition from VM root operation to VM non root operation • Loads guest state from VMCS • Stores VMM state to VMCS
- 31. VM Entry and Exit • Two types of transitions • VM entry • Transition from VM root operation to VM non root operation • Loads guest state from VMCS • Stores VMM state to VMCS • VM exit • Transition from VM non-root operation to VM root operation • Stores guest state to VMCS • Loads VMM state from VMCS
- 32. VM Entry and Exit Guest 0 Guest 1 VMM VMXON VMXOFF VM EntryVM Exit VM Exit Picture: Copied from Intel Manual Sept 2014
- 33. Virtual Machine Control Structure • Control Structures stored in memory
- 34. Virtual Machine Control Structure • Control Structures stored in memory • One VMCS active per virtual processor at a time
- 35. Virtual Machine Control Structure • Control Structures stored in memory • One VMCS active per virtual processor at a time • Stores guest state, host state, VMX controls and VM-exit information
- 36. VM Exits in VMX Non-Root Operation • Some instructions cause VM-exit unconditionally • e.g. CPUID, INVD, XSETBV, INVEPT, VMCLEAR, VMLAUNCH, etc.
- 37. VM Exits in VMX Non-Root Operation • Some instructions cause VM-exit unconditionally • e.g. CPUID, INVD, XSETBV, INVEPT, VMCLEAR, VMLAUNCH, etc. • Some instructions cause VM-exit conditionally based on VM- execution control settings in VMCS • e.g. HLT, INVLPG, MONITOR, VMREAD, etc.
- 38. VM Exits in VMX Non-Root Operation • Some instructions cause VM-exit unconditionally • e.g. CPUID, INVD, XSETBV, INVEPT, VMCLEAR, VMLAUNCH, etc. • Some instructions cause VM-exit conditionally based on VM- execution control settings in VMCS • e.g. HLT, INVLPG, MONITOR, VMREAD, etc. • Exceptions
- 39. VM Exits in VMX Non-Root Operation • Some instructions cause VM-exit unconditionally • e.g. CPUID, INVD, XSETBV, INVEPT, VMCLEAR, VMLAUNCH, etc. • Some instructions cause VM-exit conditionally based on VM- execution control settings in VMCS • e.g. HLT, INVLPG, MONITOR, VMREAD, etc. • Exceptions • Triple Faults
- 40. VM Exits in VMX Non-Root Operation • Some instructions cause VM-exit unconditionally • e.g. CPUID, INVD, XSETBV, INVEPT, VMCLEAR, VMLAUNCH, etc. • Some instructions cause VM-exit conditionally based on VM- execution control settings in VMCS • e.g. HLT, INVLPG, MONITOR, VMREAD, etc. • Exceptions • Triple Faults • External Interrupts
- 41. VM Exits in VMX Non-Root Operation • Some instructions cause VM-exit unconditionally • e.g. CPUID, INVD, XSETBV, INVEPT, VMCLEAR, VMLAUNCH, etc. • Some instructions cause VM-exit conditionally based on VM- execution control settings in VMCS • e.g. HLT, INVLPG, MONITOR, VMREAD, etc. • Exceptions • Triple Faults • External Interrupts • Non-Maskable Interrupts
- 42. VM Exits in VMX Non-Root Operation • Some instructions cause VM-exit unconditionally • e.g. CPUID, INVD, XSETBV, INVEPT, VMCLEAR, VMLAUNCH, etc. • Some instructions cause VM-exit conditionally based on VM- execution control settings in VMCS • e.g. HLT, INVLPG, MONITOR, VMREAD, etc. • Exceptions • Triple Faults • External Interrupts • Non-Maskable Interrupts and more…
- 43. References • A.S.Tanenbaum, Modern Operating Systems, 3rd Edition,2008 • Abraham Silberschatz, Peter B. Galvin, Greg Gagne, Operating System Concepts, 8th Edition, 2010 • Understanding Full Virtualization, Paravirtualization and Hardware-assist by VMware • Understanding Intel Virtualization Technology (Power point presentation) by Narendar B. Sahgal and Dion Rodgers • Intel 64 and IA-32 Architectures Software Developer’s Manual Volume 3
Editor's Notes
- Basic block is defined in compiler theory. It is a block of instructions which has single entry point and single exit point. By definition, they cannot have any instructions which can modify the program counter except at the end.
- Basic block is defined in compiler theory. It is a block of instructions which has single entry point and single exit point. By definition, they cannot have any instructions which can modify the program counter except at the end.