IO virtualization Profile
full virtualization
to simulate the IO devices to achieve through the VMM, VMM intercept IO requests GuestOS, the real hardware through software emulation. VMM must process the IO request all virtual machines, then all of the sequences into a single case IO IO stream may be processed underlying hardware. Benefit is not necessary to consider the case GuestOS hardware. The problem is the relatively low efficiency. For example qemu.
A complete packet from the virtual machine to a physical machine is the path: the virtual machine virtual NIC --QEMU - virtualization layer - core bridge - physical NIC.
Paravirtualization
virtualization is achieved by an analog front end and a rear end. GuestOS half of virtualized drive to the front, VMM provides the driver GuestOS communications for the back-end. Then sent to the front-end drivers after the physical drive request by the VMM backend GuestOS needs to occur with the specific communication mechanism between the VMM, backend driver IO request has been processed. To complete a full virtualization operation involves the operation of a plurality of registers, such that the VMM to intercept each access register and the corresponding simulation, will lead to multiple context switches. This embodiment can greatly reduce the frequency of context switching, to provide more room for optimization. For example virtio.
