Takahiro Shinagawa: Introduction to the BitVisor and Comparison with Xen

1. Xen Summit Tokyo 2008
マスタ サブタイトルの書式設定
Takahiro Shinagawa
University of Tsukuba
Introduction to BitVisor and
Comparison with Xen
2008/11/21 Xen Summit Tokyo 2008

2. What is BitVisor ?
A VMM featuring security functionalities

 Has been developed by “Secure VM Project”
A R&D project with governmental support
▪
Initiated by NISC (National Information Security Center)
▪
Funded by SCF of MEXT
▪
SCF: Special Coordination Funds for Promoting Science and Technology

MEXT: Ministry of education, culture, sports, science and technology

 developed from scratch (an all-Japanese product)
Several universities and organizations are involved
▪
* VMM: Virtual Machine
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Monitor

3. Background & Purpose
Increasing threats of information leakage

 From lost or stolen PCs and USB memories
 Through the Internet
Via viruses and P2P file-sharing software
▪
Using a VMM to prevent information leakage

 Enforce encryption and authentication
Encrypt storages and networks
▪
▪ Authenticate with smart cards
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4. Functions of the BitVisor
Storage management Guest OS

 Encryption of HDDs
and USB memories ＶＭＭ
Storage ID Network
management management management
Encryptio Auth & VPN
n Keys
ID management
 VMM core
Hardware Virtualization
 Key & ID management
Hardware
using smart cards
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5. Assumptions behind Design
Decisions
Security of the VMM itself is important

 VMM should be kept as small as possible
Used in desktop environments

 Windows is the target OS to be secured
Limited development cost & period

 3 years, 5 full-time researchers, limited budget
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6. Para Pass-through Architecture
Pass-through most I/Os

Guest OS
 Guest handles the devices Device Driver
Devices are not virtualized
▪
Para pass-through VMM
Parapass-through driver
Intercept partial I/Os Control I/Os Other I/Os Data I/Os

Pass-through
Access Encryption
Control
 Control I/Os are monitored Hardware
Device
for access control
▪
 Data I/Os are converted
▪ for encryption
66
2008/11/21 Xen Summit Tokyo 2008

7. Advantages
The VMM becomes small

 CPU & memory virtualization is simplified
No scheduling and protection among VMs
▪
 Drivers are simplified
Need to handle only control I/Os and data I/Os
▪
Overhead becomes lower

 Pass-through most I/Os
▪ Even Windows Vista Aero will work
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8. Disadvantages
Multiple OSes cannot run simultaneously

 The guest OS directly handles the devices
-> Acceptable since the target is desktop computers
Hardware support is limited

 A driver is required for each (monitored) device
-> Acceptable in office (government) environments
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9. Comparison with other VMMs
Type II VMM
 Guest OS Guest OS
VMM
Device Model
 TCB = Host OS + VMM
Host OS
Device Driver
Ex. Linux(56M LOC)+QEMU(310K LOC)
▪
hardware
Guest OS Guest OS
VMM
Device Model
Type I VMM

Device Driver
 VMM has device model and drivers hardware
Ex. VMWare ESX hypervisor has 200K LOC
▪
* LOC: Lines Of
Code
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10. Comparison with Xen (Size)
Xen

Guest
Domain 0
 VMM (hypervisor) is relatively small OS
Device
Model
Device Driver
About 100 K LOC [Murray et al. VEE2008]
▪ VMM
hardware
 TCB is not necesssarily small
Including Domain 0
▪
BitVisor

 VMM is small
▪ VMM core has about 20 K LOC
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11. Comparison with Xen (Overhead)
Xen BitVisor
Need scheduling among Yes No
VMs (support multiple (support only
VMs) single VM)
Need shadow paging Yes Yes
(for address (for protection of
translation and the VMM)
protection among
VMs and the
VMM)
- Shadow paging Optimized Preliminary
implementation (EPT/NPT will help)
Device driver Para- Parapass-through
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12. Experimental Setup
Hardware

 Intel Core 2 Duo E8600 (3.33GHz)
 4GB memory
 10,000rpm HDD
(Western Digital Raptor WD740GD)
▪
Software

 VMM: BitVisor 0.3 (64bit)
 Guest OS: Fedora 9Tokyo 2008 Windows Vista (64bit)
Xen Summit (64bit),
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13. Experimental Result 1
Now Printing
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14. Experimental Result 2
Now Printing
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15. Summary
A Secure VMM called BitVisor was introduced

 Encryption of storages and networks
 Authentication and key management using smart
cards
Comparisons with Xen were presented

 Difference in the architectures
Para-virtualization v.s. Para-passthrough
▪
 Difference in the performances
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16. Current Status
BitVisor 0.7 has been (will be) released

 Intel VT, 32/64bit, and SMP/Multicore
Also AMD SVM (single processor only)
▪
 Major operating systems are supported
Windows Vista/XP, Linux, FreeBSD, ...
▪
 HDD encryption (ATA only)
 USB memory encryption (UHCI only)
 Type B smart cards
 IPsec VPN (Intel PRO100 only)
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17. Download
http://www.securevm.org/
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