Observed on MPCBL0050 board with 16G RAM. With 16G RAM setup, kernel failed to find RSDP, and will crash afterwards (refer to the log files from the Attachments). But can start up with ACPI disabled, or with 8G RAM setup and ACPI enabled.
The problem occurs very early on, when the kernel allocates space for the
temporary memory map called bootmap. The bootmap overlaps the EBDA region.
EBDA region is not historically reserved in the e820 mapping. When the
bootmap is freed it marks the EBDA region as usable.
If you notice in setup.c there is already code to work around the EBDA
in reserve_ebda_region(), this check however occurs after the bootmap
is allocated and doesn't prevent the bootmap from using this range. IDENTIFIER = WIND00122788
