Hi,
On 04.11.20 23:21, Angel Pons wrote:
- Please take a look at the preliminary release notes in
Documentation/releases/coreboot-4.13-relnotes.md and add whatever happened since 4.12 that is worth mentioning. If unsure, simply push a change to Gerrit and have your fellow developers discuss it.
I have a candidate for a deprecation warning: We're currently working to make all not (clearly) necessary PCI bus master enabling optional. The added Kconfig option still defaults to `y` [1], for compatibility reasons. This has security implications and hence I propose to proceed as follows:
After the follow-up (spring) release, * remove the option and the code using it, or at least * reduce its usage to a minimum and change the default to `n`.
This should give people enough time to test (with the option disabled) and potentially fix their payloads (and OS?). If there are no concerns, I'll add that to the release notes.
There are cases where enabling PCI bus mastering already in coreboot might be necessary. For instance, Intel documents for their integrated graphics to enable it before the initialization sequence (without tel- ling us why and tests show that it ignores the bit anyway *shrug*). And also cases where it's clearly necessary, e.g. before hiding a PCI devices configuration space to put it into ACPI mode (if the OS is not aware of the device' PCI nature, it can't know that bus mastering needs to be enabled).
If anybody knows or discovers more cases where it needs to be enabled in advance by coreboot, please mention it here.
Nico