Microsoft Better Seeds The RNG For Hyper-V VMs In Linux 6.9

Written by Michael Larabel in Microsoft on 21 March 2024 at 06:30 AM EDT. 2 Comments
Microsoft has submitted their various Hyper-V updates to the in-development Linux 6.9 kernel.

Most of the Hyper-V updates for Linux 6.9 are small, low-level changes but one worth mentioning is that Hyper-V entropy will now be used to better seed the guest random number generator (RNG) for VMs.

Current generation Hyper-V VMs already use the EFI RNG protocol for obtaining some entropy during the early boot phase, but Hyper-V does provide more entropy via a custom ACPI table named "OEM0". With Linux 6.9 is now support for obtaining entropy from Microsoft's OEM0 table for Hyper-V VMs to obtain more entropy than just from the EFI RNG protocol. Additionally, this new method works for Gen1 Hyper-V VMs being booted via the BIOS rather than UEFI. Those older VMs don't obtain any entropy from the Hyper-V host right now but with Linux 6.9+ will obtain entropy from OEM0 for seeding the RNG.

The handful of other patches making up the Hyper-V pull request for Linux 6.9 are all minor items.
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