Intel i5-2500K BX80623I52500K User Manual

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Datasheet, Volume 1

The processor core supports the following Intel VT-x features:

• Extended Page Tables (EPT)

— EPT is hardware assisted page table virtualization
— It eliminates VM exits from guest OS to the VMM for shadow page-table 

maintenance

• Virtual Processor IDs (VPID)

— Ability to assign a VM ID to tag processor core hardware structures (such as 

TLBs) 

— This avoids flushes on VM transitions to give a lower-cost VM transition time 

and an overall reduction in virtualization overhead.

• Guest Preemption Timer

— Mechanism for a VMM to preempt the execution of a guest OS after an amount 

of time specified by the VMM. The VMM sets a timer value before entering a 

guest

— The feature aids VMM developers in flexibility and Quality of Service (QoS) 

assurances

• Descriptor-Table Exiting

— Descriptor-table exiting allows a VMM to protect a guest OS from internal 

(malicious software based) attack by preventing relocation of key system data 

structures like IDT (interrupt descriptor table), GDT (global descriptor table), 

LDT (local descriptor table), and TSS (task segment selector). 

— A VMM using this feature can intercept (by a VM exit) attempts to relocate 

these data structures and prevent them from being tampered by malicious 

software.

The key Intel VT-d objectives are domain-based isolation and hardware-based 
virtualization. A domain can be abstractly defined as an isolated environment in a 
platform to which a subset of host physical memory is allocated. Virtualization allows 
for the creation of one or more partitions on a single system. This could be multiple 
partitions in the same operating system, or there can be multiple operating system 
instances running on the same system – offering benefits such as system 
consolidation, legacy migration, activity partitioning, or security.