Intel Enabling Resizable BAR To Work With I/O Virtualization On Linux
Written by Michael Larabel in Hardware on 16 December 2021 at 04:37 AM EST. 3 Comments
HARDWARE --
Resizable BAR support (also known as ReBAR / AMD Smart Access Memory) has been popular with gamers for supported configurations for being able to improve GPU performance. Intel is now working on enabling the Linux kernel to support Resizable BAR when in the context of I/O Virtualization.

Resizable BAR is a PCI Express feature can allow for the entire vRAM contents to be accessible by the CPU rather than being limited to a 256MB window. In turn that can lead to more efficient transfers between the CPU and GPU, but is contingent upon CPU/GPU/system support. Linux has supported Resizable BAR behavior as part of the PCIe specification and various Linux graphics drivers do make use of Resizable BAR in capable system configurations.

The new patches being worked on by Intel are for enabling Resizable BAR support in the PCI VF (Virtual Function) code so that existing ReBAR query/enabling interface can work with I/O Virtualization (IOV) BAR as well. This in turn should be useful for those assigning a graphics card via SR-IOV for gaming within a virtual machine and the like to be able to enable Resizable BAR.

That in-progress Resizable BAR support for IOV can be found via this patch thread.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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