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  • 1. SSG System Software Division Virtualization Technology Overview Liu, Jinsong (jinsong.liu@intel.com)
  • 2. 2012/11/282 Agenda •Introduction  history  Usage model •Virtualization overview  cpu virtualiztion  memory virtualization  I/O virtualization •Xen/KVM architecture  Xen  KVM •Some intel work for Openstack  OAT
  • 3. 2012/11/283 Virtualization history • 60s’ IBM - CP/CMS on S360, VM370, … • 70’s 80s’ Silence • 1998 VMWare - SimOS project, Stanford • 2003 Xen - Xen project, Cambridge • After that: KVM/Hyper-v/Parallels …
  • 4. 2012/11/284 What is Virtualization • VMM is a layer of abstraction  support multiple guest OSes  de-privilege each OS to run as Guest OS • VMM is a layer of redirection  redirect physical platform to virtual platform illusions of many  provide virtaul platfom to guest os ... Virtual Machine Monitor (VMM) VMnVM0 Guest OS VM1 Platform HW I/O DevicesProcessorsMemory Apps Guest OS Apps Guest OS Apps ... Virtual Machine Monitor (VMM) VMnVM0 Guest OS VM1 Platform HW I/O DevicesProcessorsMemory Apps Guest OS Apps Guest OS Apps
  • 5. 2012/11/285 Server Virtualization Usage Model Server Consolidation Benefit: Cost Savings • Consolidate services • Power saving HWHW HW VMM Disaster Recovery HW VMM HW VMM … OS App OS App OS App … OS App HW VMM HW VMM • Benefit: Productivity Dynamic Load Balancing OS App 1 OS App 2 OS App 3 OS App 4 CPU Usage 30% CPU Usage 90% CPU Usage CPU Usage Benefit: Business Agility and Productivity R&D Production HW VMM OS App Benefit: Lost saving • RAS • live migration • relief lost
  • 6. 2012/11/286 Agenda •Introduction •Virtualization overview  CPU virtualization  Memory virtualization  I/O virtualization •Xen/KVM architecture •Some intel work for Openstack
  • 7. 2012/11/287 X86 virtualization challenges • Ring Deprivileging  Goal: isolate guest OS from • Controlling physical resources directly • Modifying VMM code and data  Ring deprivileging layout • vmm runs at full privileged ring0 • Guest kernel runs at • X86-32: deprivileging ring 1 • X86-64: deprivileging ring 3 • Guest app runs at ring 3  Ring deprivileging problems • Unnecessary faulting • some privilege instructions • some exceptions • Guest kernel protection (x86-64) • Virtualization holes  19 instructions • SIDT/SGDT/SLDT … • PUSHF/POPF …  Some userspace holes hard to fix by s/w approach • Hard to trap, or • Performance overhead
  • 8. 2012/11/288 X86 virtualization challenges Virtual Machine Monitor (VMM)Virtual Machine Monitor (VMM) VM0 Guest OS Apps VM0 Guest Kernel Guest Apps VM0 Guest OS Apps VM1 Guest Kernel Guest Apps VM0 Guest OS Apps VM2 Guest Kernel Guest Apps Ring0 Ring1 Ring3
  • 9. 2012/11/289 Typical X86 virtualization approaches • Para-virtualization (PV)  Para virtualization approach, like Xen  Modified guest OS aware and co-work with VMM  Standardization milestone: linux3.0 • VMI vs. PVOPS • Bare metal vs. virtual platform • Binary Translation (BT)  Full virtualization approach, like VMWare  Unmodified guest OS  Translate binary ‘on-the-fly’ • translation block w/ caching, • usually used for kernel, ~80% native performance • userspace app directly runs natively as much as possible, ~100% native performance • overall ~95% native performance • Complicated • Involves excessive complexities. e.g., self-modifying code • Hardware-assisted Virtualization (VT)  Full virtualization approach assisted by hardware, like KVM  Unmodified guest OS  Intel VT-x, AMD-v  Benefits: • Closing virtualization holes in hardware • Simplify VMM software • Optimizing for performance
  • 10. 2012/11/2810 Memory virtualization challenges • Guest OS has 2 assumptions  expect to own physical memory starting from 0 • BIOS/Legacy OS are designed to boot from address low 1M  expect to own basically contiguous physical memory • OS kernel requires minimal contiguous low memory • DMA require certain level of contiguous memory • Efficient MM management, e.g., less buddy overhead • Efficient TLB, e.g., super page TLB • MMU virtualization  How to keep physical TLB valid  Different approaches involve different complication and overhead
  • 11. 2012/5/1311 Machine Physical Memory Hypervisor Guest Pseudo Physical Memory 5 1 3 2 4 3 2 1 4 5 VM1 VM4VM3VM2 Memory virtualization challenges
  • 12. 2012/11/2812 Memory virtualization approaches • Direct page table  Guest/VMM in same linear space  Guest/VMM share same page table • Shadow page table  Guest page table unmodified • gva -> gpa  VMM shadow page table • gva -> hpa  Complication and memory overhead • Extended page table  Guest page table unmodified • gva -> gpa • full control CR3, page fault  VMM extended page table • gpa -> hpa • hardware based • good scalability for SMP • low memory overhead • Reduce page fault VMexit greatly • Flexible choices  Para virtualization • Direct page table • Shadow page table  Full virtualization • Shadow page table • Extended page table GVA GPA HPA Extended page table Shadow page table Direct page table Guest page table
  • 13. 13 Shadow page table • Guest page table remains unmodified to guest  Translate from gva -> gpa • Hypervisor create a new page table for physical  Use hpa in PDE/PTE  Translate from gva -> hpa  Invisible to guest Page Directory Page Table PDE PTE Page Directory Page Table PDE PTE vCR3 pCR3 Virtual Physical 2012/11/28
  • 14. 14 • Extended page table  Guest can have full control over its page tables and events • CR3, INVLPG, page fault  VMM controls Extended Page Tables • Complicated shadow page table is eliminated • Improved scalability for SMP guest Guest Page Tables Extended Page Tables Guest Physical Address Host Physical Address Guest Linear Address Guest CR3 EPT base pointer Extended page table 2012/11/28
  • 15. 2012/11/2815 I/O virtualization requirements • I/O device from OS point of view  Resource configuration and probe  I/O request: IO, MMIO  I/O data: DMA  Interrupt • I/O Virtualization require  presenting guestos driver a complete device interface • Presenting an existing interface • Software Emulation • Direct assignment • Presenting a brand new interface • Paravirtualization Device CPU Shared Memory Interrupt Register Access DMA
  • 16. 2012/11/2816 I/O virtualization approaches • Emulated I/O  Software emulates real hardware device  VMs run same driver for the emulated hardware device  Good legacy software compatibility  Emulation overheads limit performance • Paravirtualized I/O  Uses abstract interfaces and stack for I/O services  FE driver: guest run virtualization-aware drivers  BE driver: driver based on simplified I/O interface and stack  Better performance over emulated I/O • Direct I/O  Directly assign device to Guest • Guest access I/O device directly • High performance and low CPU utilization  DMA issue • Guest set guest physical address • DMA hardware only accept host physical address  Solution: DMA Remapping (a.k.a IOMMU) • I/O page table is introduced • DMA engine translate according to I/O page table  Some limitations under live migration
  • 17. 2012/11/2817 Virtual platform models ULM Hypervisor Host OS Guest OS Guest Apps LKM Guest OS Guest Apps ULM U-Hypervisor Service VMPreferred OS Apps P Processor Mgt code M Memory Mgt code DR Device Driver DM Device Model P P PM M M DR DR DR DM DM Hypervisor Model DM Host-based Model Hybrid Model N NoDMA N Preferred OS Apps Guest OS Guest Apps
  • 18. 2012/11/2818 Agenda •Introduction •Virtualization •Xen/KVM architecture •Some intel work for Openstack
  • 19. 2012/11/2819 Xen Architecture 0P 1/3P 3P I/O: PIT, APIC, PIC, IOAPICProcessor Memory Control Interface HypercallsEvent ChannelScheduler Inter-domain Event Channels Xen Hypervisor FrontendVirtual Drivers XenLinux64 DomainU Backend Virtualdriver Callback / Hypercall Native Device Drivers Control Panel (xm/xend) XenLinux64 Domain 0 Device Models Virtual Platform VM Exit 0D HVM Domain (64-bit) 3D Guest BIOS Unmodified OS FE Drivers Virtual Platform VM Exit Guest BIOS Unmodified OS FE Drivers HVM Domain (32-bit)
  • 20. 2012/11/2820 KVM Architecture VMCS VMCS VMCS vCPU vMEM vTimer vPIC vAPIC vIOAPIC Windows Guest Linux Guest Qemu-kvm Linux Kernel Root Non Root KVM module
  • 21. 2012/11/2821 Agenda •Introduction •Virtualization •Xen/KVM architecture •Some intel work for Openstack
  • 22. Trusted Pools - Implementation Attestation Service Scheduler EC2APIOSAPI Query API User specifies :: Mem > 2G Disk > 50G GPGPU=Intel trusted_host=trusted HW/TXT Hypervisor / tboot OS App App App OS App App App Host agent Attestation Server Privacy CA Appraiser Whitelist DB Whitelist API HostAgentAPI QueryAPI OpenStack TrustedFilterCreate Attest Report Query trusted/ untrusted Create VM OAT- Based Tboot- Enabled