proxmox serial port pass through definition

Proxmox Serial Port Pass Through Definition Driver In The

For example, if a system included multiple video adapters, those adapters could be passed through to unique guest domains.

But platform implies more than just a processor: it also includes the other important elements that make up a platform, including storage, networking, and other hardware resources.

Some hardware resources can easily be virtualized, such as the processor or storage, but other hardware resources cannot, such as a video adapter or a serial port.

Peripheral Component Interconnect (PCI) passthrough provides the means to use those resources efficiently, when sharing is not possible or useful.

This article explores the concept of passthrough, discusses its implementation in hypervisors, and details the hypervisors that support this recent innovation.

The first architecture incorporates device emulation within the hypervisor, while the second pushes device emulation to a hypervisor-external application.

In this model, the hypervisor includes emulations of common devices that the various guest operating systems can share, including virtual disks, virtual network adapters, and other necessary platform elements.

QEMU (which provides not only device emulation but a hypervisor as well) provides for device emulation and is used by a large number of independent hypervisors (Kernel-based Virtual Machine KVM and VirtualBox being just two).

This model is advantageous, because the device emulation is independent of the hypervisor and can therefore be shared between hypervisors.

It also permits arbitrary device emulation without having to burden the hypervisor (which operates in a privileged state) with this functionality.

The most important advantage relates to whats called the trusted computing base (TCB).

The TCB of a system is the set of all components that are critical to its security.

The security of the hypervisor is crucial, as it isolates multiple independent guest operating systems.

With less code in the hypervisor (pushing the device emulation into the less privileged user space), the less chance of leaking privileges to untrusted users.

Device emulation can mimic a specific device (such as a Novell NE1000 network adapter) or a specific type of disk (such as an Integrated Device Electronics IDE drive).

The physical hardware can differ greatlyfor example, while an IDE drive is emulated to the guest operating systems, the physical hardware platform can use a serial ATA (SATA) drive.

This is useful, because IDE support is common among many operating systems and can be used as a common denominator instead of all guest operating systems supporting more advanced drive types.

Whether device emulation is performed in the hypervisor or in user space within an independent VM, overhead exists.

This overhead is worthwhile as long as the devices need to be shared by multiple guest operating systems.

If sharing is not necessary, then there are more efficient methods for sharing devices.

But why is this useful Not surprisingly, there are a number of reasons why device passthrough is worthwhile.

Two of the most important reasons are performance and providing exclusive use of a device that is not inherently shareable.

Proxmox Serial Port Pass Through Definition Driver In The

This is perfect for networking applications (or those that have high disk IO) that have not adopted virtualization because of contention and performance degradation through the hypervisor (to a driver in the hypervisor or through the hypervisor to a user space emulation).

But assigning devices to specific guests is also useful when those devices cannot be shared.