Hypervisors
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The document discusses hypervisors and virtualization, highlighting the need for organizations to use multiple virtual systems on a single physical machine for reliability and efficiency. It explains different types of hypervisors (Type 1 and Type 2), virtualization requirements, and various implementation techniques like binary translation and paravirtualization. Furthermore, it outlines the hardware support introduced by Intel with its VT-x technology and describes the operations and transitions involved in virtual machine control.
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
- #21: 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.
- #22: 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.