On 5/23/2024 2:17 AM, Du Lin wrote:
Thanks for the quick response.
Agree that the PI and UEFI specs are vague on SP. That is also why I opted to
minimize code changes to DXE core for SP support in patch
https://edk2.groups.io/g/devel/message/118712.
Would it make more sense to let the caller determine if SP memory is available
for UEFI via EFI resource types (e.g., EFI_RESOURCE_SYSTEM_MEMORY vs
EFI_RESOURCE_MEMORY_RESERVED)?
CDAT can be read in PEI phase via DOE method and CDAT is important to support CXL 2.0. I
believe CDAT spec is referencing EFI_MEMORY_TYPE and Memory Attributes defined in UEFI
spec section 7.2. "EfiConventionalMemory Type with EFI_MEMORY_SP Attribute" may
suggest that the memory type shall be EfiConventionalMemory and the attribute shall have
SP set when reporting the memory to OS. And the concern is whether this combination can
still be supported if we always mark resource HOBs with SP set as
EfiGcdMemoryTypeReserved.
Thanks for the clarification. I agree that it makes sense to let the
resource HOB creator determine whether UEFI will put this in
system memory or reserved memory. DxeCore at that point could decide
to not allocate any memory with the EFI_MEMORY_SP attribute (or it
could decide it doesn't care).
We are meeting with some CXL stakeholders to make sure there is no
concern with changing this patch and then we will respin this.
Thanks,
Oliver
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