ACPI Platform Runtime Mechanism Support Is Getting Underway For Linux

Written by Michael Larabel in Hardware on 14 June 2021 at 08:00 AM EDT. 4 Comments
Platform Runtime Mechanism was incorporated into the ACPI 6.4 specification earlier this year and allows moving some system management interrupt (SMI) handlers out of the system management mode (SMM) "black box" and into the OS/VMM execution context. With Linux 5.14 initial work on ACPI Platform Runtime Mechanism is set to land.

Platform Runtime Mechanism, allows moving of the SMI handlers that do not require SMM privileges to be punted into the OS/VMM context. There are security and performance benefits of PRM and with it now being part of the public ACPI specification, the Linux kernel support is on its way. Microsoft for their part has already offered PRM support as part of Windows Insider Preview builds for months.

More background information on the Platform Runtime Mechanism can be found via the prior article Intel + Microsoft Continue Work On Replacing More SMM "Black Boxes" With PRM.

Now on the kernel front for the upcoming Linux 5.14, an initial PRM pull has landed into linux-pm's -next code. The pull has the initial changes for PRM and implementing the OperationRegion handler for this mechanism. A new Kconfig build time knob of ACPI_PRMT is added for that Platform Runtime Mechanism support.

More PRM technical information in general is available from the documentation.
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