Two independent layers of paging will interact, perform poorly.
Guest OS incorrectly believe a page to be in physical memory ( green/gold pages ) VMM believes an unneeded page is still in use (teal pages) Guest evicts a page despite available physical memory (red pages)
Driver allocate pinned physical pages within the VM
Increase memory pressure in the guest OS, reclaim space to satisfy the driver allocation request
Driver communicates the physical page number for each allocated page to ESX server
Frees up memory for general use within the guest OS
Virtualizing I/O Devices on VMware Workstation
Supported v irtual devices of V Mwa re
PS/2 keyboard, PS/2 mouse, floppy drive, IDE controllers with ATA disks and ATAPI CD-ROMs, a Soundblaster 16 sound card, serial and parallel ports, virtual BusLogic SCSI controllers, AMD PCNet Ethernet adapters, and an SVGA video controller.
I ntercept I/O operations issued by the guest OS. ( IA-32 IN and OUT )
E mulated either in the VMM or the VMApp.
Virtualizing I/O devices can incur overhead from world switches between the VMM and the host
H andling the privileged instructions used to communicate with the hardware
Case Study: The Intel VT-x (Vanderpool) Technology
enhance the performance VM implementation through hardware enhancements of the processor.
The inclusion of the new VMX mode of operation (VMX root/non-root operation)
VMX root operation
Fully privileged, intended for VM monitor New instructions – VMX instructions
VMX non-root operation
Not fully privileged, intended for guest software
Reduces Guest SW privilege w/o relying on rings
Technological Overview Root Mode (VMM) Non-Root (VM1) Non-Root (VM2) Regular Mode Regular Mode vmxon v mlaunch VM1 v mlaunch VM2 v mresume VM2 v mresume VM2 v mresume VM1 vmxoff VM1 exits VM2 exits VM2 exits VM2 exits VM1 exits
VT-x Operations IA-32 Operation VMX Root Operation VMX Non-root Operation . . . VMXON VMLAUNCH VMRESUME VM Exit Ring 0 Ring 3 Ring 0 Ring 3 VM 1 Ring 0 Ring 3 VM 2 Ring 0 Ring 3 VM n VMCS 2 VMCS n VMCS 1