Hello!
Could someone correct my understanding of reserved memory regions?
I want to reserve some region (below 4G) but this region must be
accessible for OS.
To be clear this is ACPI NVS region which must be accessible for Linux
Kernel, i.e request_mem_region() must succeed.
So what I am doing:
On PEI phase I create two HOBs:
BuildResourceDescriptorHob (
EFI_RESOURCE_SYSTEM_MEMORY,
EFI_RESOURCE_ATTRIBUTE_PRESENT |
EFI_RESOURCE_ATTRIBUTE_INITIALIZED |
EFI_RESOURCE_ATTRIBUTE_UNCACHEABLE |
EFI_RESOURCE_ATTRIBUTE_WRITE_COMBINEABLE |
EFI_RESOURCE_ATTRIBUTE_WRITE_THROUGH_CACHEABLE |
EFI_RESOURCE_ATTRIBUTE_WRITE_BACK_CACHEABLE |
EFI_RESOURCE_ATTRIBUTE_TESTED,
BASE_1MB,
LowerMemorySize - ReservedMemorySize)
);
BuildResourceDescriptorHob (
EFI_RESOURCE_MEMORY_RESERVED,
EFI_RESOURCE_ATTRIBUTE_PRESENT |
EFI_RESOURCE_ATTRIBUTE_INITIALIZED |
EFI_RESOURCE_ATTRIBUTE_UNCACHEABLE |
EFI_RESOURCE_ATTRIBUTE_TESTED,
ReservedMemoryBase,
ReservedMemorySize
);
So, DXE phase will not use reserved memory.
To insert this reserved memory region to EFI memory map I call
gBS->AllocatePages (
AllocateAddress,
EfiACPIMemoryNVS,
EFI_SIZE_TO_PAGES (ReservedMemorySize),
ReservedMemoryBase
);
So, everyone is happy, OS kernels (Linux, Windows) successfully maps
this memory.
But CSM LegacyBiosDxe asserts.
LegacyBiosBuildE820 function detects overlapped memory region, because
it processes
EFI memory map and HOB list during E820 map building.
AllocatePages() adds this region to memory map, while HOB list still
contains it also.
So here is a question: Am I reserve memory region correctly or there is
a some inaccuracy at LegacyBiosDxe?
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