Linux 5.14 To Support XMM Fast Hypercalls For Hyper-V On KVM
Written by Michael Larabel in Virtualization on 24 June 2021 at 12:00 AM EDT. 2 Comments
VIRTUALIZATION --
With the KVM code set to be merged in the coming weeks for the Linux 5.14 kernel, support for fast XMM hypercalls is coming for its Hyper-V guest support in allowing for some performance benefits.

Microsoft Hyper-V's hypercall interface - for the calling mechanism into guests - supports the notion of XMM fast hypercalls. The XMM fast hypercall support allows for some calls to enjoy improved performance. This fast hypercalls interface makes use of six XMM registers compared to otherwise the maximum of two general purpose registers for hypercalls.

The XMM fast hypercalls details are outlined via the Microsoft documentation.

Amazon engineers for Linux 5.14 have contributed support for advertising XMM fast hypercall support to Hyper-V guests within KVM. The necessary patches were queued and thus the feature now advertised with the material in kvm.git's "-next" branch. Amazon is planning on contributing more Linux kernel patches for other hypercall interfaces that make use of this functionality moving forward.
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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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