Hello:
I have a question which might not be applicable to the stock Tianocore
codebase, but I'm hoping maybe someone here might recognize what I'm asking
about and could give me some pointers.
I have A Board (tm) with Intel Raptor Lake CPU and a UEFI 2.7-based firmware
implementation on it. Out of the box, if I go to the UEFI shell and run the
memmap command, I can see there is a gap in the available RAM starting at the
2MB mark. That is, I see this:
Available 0000000000100000-00000000001FFFFF 0000000000000100 000000000000000F
Available 0000000000201000-00000000339A6FFF 00000000000337A6 000000000000000F
Near the end of the output, I also see this:
Reserved 0000000000200000-0000000000200FFF 0000000000000001 0000000000000000
The implication is that the UEFI firmware has, for some reason, decided to
reserve the page of memory at 0x200000 for some nefarious purpose.
As it happens, this is extremely inconvenient for my purposes. In the past
I've seen where the OVMF UEFI images for Intel will try to reserve a block at
the 8MB mark for stashing things during S3 hibernation mode, and I've been
able to work around that by using the -global ICH9-LPC.disable_s3=1 command
line flag with QEMU.
But in this case, I have no idea why the firmware is reserving this page. There
are ACPI_NVS and ACPI_Reclaim ranges too, but they are further up in RAM and
not a concern for me.
The only clue I have is that if I dump the page at 0x200000 from the shell
using the mem command, I see that it contains the string 'TERR' at the start,
and a few numbers within the first 32 bytes, and the rest is all zeroes. This
suggests some sort of anchor string, but I don't know what it means.
Can anybody think of what this reserved page is for, and if maybe the firmware
setup menu might offer me a way to turn off whatever feature is reserving it?
(For the record, there is an option to disable S3 sleep support and I did try
turning that off, but it made no difference.)
Thanks in advance.
-Bill
--
=============================================================================
-Bill Paul (510) 749-2329 | VxWorks Software Architect,
wp...@windriver.com | Master of Unix-Fu - Wind River Systems
=============================================================================
"I put a dollar in a change machine. Nothing changed." - George Carlin
=============================================================================
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