From 4d4f56992460c039d0cfe48c394c2e07aecf1d22 Mon Sep 17 00:00:00 2001
From: Dhaval <dhaval@rivosinc.com>
Date: Tue, 18 Jun 2024 21:19:05 +0530
Subject: MdeModulePkg: Avoid efi memory allocation for SP memory

HBM/CXL memory systems are treated as special purpose memories. In many
cases it is desirable not to use special purpose memory for regular edk2
usages as these memories (HBm/CXL) are either meant for special purposes
or are less reliable to be used. Until such memory systems evolve and
we have better clarity from UEFI spec, avoid using them for edk2
boot memory purposes.

Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Oliver Smith-Denny <osde@linux.microsoft.com>
Signed-off-by: Dhaval Sharma <dhaval@rivosinc.com>
Co-authored-by: Tim Wawrzynczak <tim@rivosinc.com>
---
 MdeModulePkg/Core/Dxe/Mem/Page.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/MdeModulePkg/Core/Dxe/Mem/Page.c b/MdeModulePkg/Core/Dxe/Mem/Page.c
index 5a51d9d..e4daa74 100644
--- a/MdeModulePkg/Core/Dxe/Mem/Page.c
+++ b/MdeModulePkg/Core/Dxe/Mem/Page.c
@@ -1183,6 +1183,13 @@ CoreFindFreePagesI (
       continue;
     }
 
+    //
+    // Don't allocate out of Special-Purpose memory.
+    //
+    if ((Entry->Attribute & EFI_MEMORY_SP) != 0) {
+      continue;
+    }
+
     DescStart = Entry->Start;
     DescEnd   = Entry->End;
 
-- 
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