# coreboot 4.15

coreboot 4.15 was released on November 5th, 2021.

Since 4.14 there have been more than 2597 new commits by more than 219 developers. Of these, over 73 contributed to coreboot for the first time.

Welcome to the project!

Thank you to all the developers who continue to make coreboot the great open source firmware project that it is.

## Important Announcement

We are going to be changing the cadence from every 6 months, to every 3 months. That means the 4.16 release will be coming in February, 2022.

## New mainboards

- Asus p8h61-m_pro_cm6630

- Asus p8h77-v

- Asus p8z77-v

- Google nipperkin

- Lenovo w541

- Siemens mc_ehl

- Supermicro x9sae

- System76 addw1

- System76 addw2

- System76 bonw14

- System76 darp6

- System76 darp7

- System76 galp2

- System76 galp3

- System76 galp3-b

- System76 galp4

- System76 galp5

- System76 gaze14

- System76 lemp10

- System76 oryp7

- System76 oryp8

## Removed mainboards

- Google Mancomb

## Deprecations and incompatible changes

### COREBOOTPAYLOAD option

Drop the deprecated COREBOOTPAYLOAD option, and replace it with MrChromebox’s updated UefiPayloadPkg option. Simplify the Kconfig options to make it easier to build from upstream edk2 master. Drop the EDK2_USE_8254_TIMER Kconfig option since it applies only to CorebootPayloadPkg. Clean up the Makefile now that we’re only building from a single edk2 package/target.

### Remove old lp4x and ddr4 versions of spd_tools

The migration to the new unified version of spd_tools is complete, so the old lp4x and ddr4 versions can be removed.

### Remove AMD PI 00630F01

No board currently uses AMD PI 00630F01 so remove it.

## Significant changes

### Merged family of Asus mainboards using H61 chipset

By using newer coreboot features like board variants and override devicetrees, lots of code can now be shared. This should ease maintenance and also make it easier for newcomers to add support for even more mainboards.

### Changed default setting for Intel chipset lockdown

Previously, the default behaviour for Intel chipset lockdown was to let the FSP do it. Since all related mainboards used the coreboot mechanisms for chipset lockdown, the default behaviour was changed to that.

### Payloads unit testing

Libpayload now supports the mock architecture, which can be used for unit testing payloads. (For examples see depthcharge payload)

### Unit testing infrastructure

Unit testing of libpayload is now possible in the same fashion as in the main coreboot tree.

### Introduce new method for accessing cpu_info

There is currently a fundamental flaw in the current cpu_info() implementation. It assumes that current stack is CONFIG_STACK_SIZE aligned. This assumption breaks down when performing SMM relocation.

The first step in performing SMM relocation is changing the SMBASE. This is accomplished by installing the smmstub at 0x00038000, which is the default SMM entry point. The stub is configured to set up a new stack with the size of 1 KiB (CONFIG_SMM_STUB_STACK_SIZE), and an entry point of smm_do_relocation located in RAMSTAGE RAM.

This means that when smm_do_relocation is executed, it is running in SMM with a different sized stack. When cpu_info() gets called it will be using CONFIG_STACK_SIZE to calculate the location of the cpu_info struct. This results in reading random memory. Since cpu_info() has to run in multiple environments, we can’t use a compile time constant to locate the cpu_info struct.

This CL introduces a new way of locating cpu_info. It uses a per-cpu segment descriptor that points to a per-cpu segment that is allocated on the stack. By using a segment descriptor to point to the per-cpu data, we no longer need to calculate the location of the cpu_info struct. This has the following advantages:

- Stacks no longer need to be CONFIG_STACK_SIZE aligned.

- Accessing an unconfigured segment will result in an exception. This ensures no one can call cpu_info() from an unsupported environment.

- Segment selectors are cleared when entering SMM and restored when leaving SMM.

- There is a 1:1 mapping between cpu and cpu_info. When using COOP_MULTITASKING, a new cpu_info is currently allocated at the top of each thread’s stack. This no longer needs to happen.