Microsoft Hyper-V Guests Get PCID Support With Linux 4.16
Written by Michael Larabel in Microsoft on 30 January 2018 at 05:26 AM EST. Add A Comment
MICROSOFT --
With the in-development Linux 4.16 kernel there is now support for PCID with Microsoft Hyper-V virtualization guests.

Up until now support for PCID (Process Context Identifiers) was intentionally disabled for Hyper-V guests with the code never having been tested for how it works on PCID-enabled systems. But Red Hat developers have now determined it's safe to enable and the switch is happening for Linux 4.16.

The timing is notable because Process Context Identifiers have been getting a lot of fanfare recently with PCID support being beneficial to lessening the impact of Kernel Page Table Isolation (KPTI). When PCID support is present for KPTI, the TLB flush can generally be avoided. PCID support has been available since the Intel Westmere days.

So this PCID change for Hyper-V guests should be beneficial for performance reasons to up-to-date Hyper-V guests.

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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 10,000 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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