[edk2-devel] [PATCH 1/3] OvmfPkg/PlatformInitLib: check PcdUse1GPageTable

[Gerd Hoffmann]

If PcdUse1GPageTable is not enabled restrict the physical address space
used to 1TB, to limit the amount of memory needed for identity mapping
page tables.

The same already happens in case the processor has no support for
gigabyte pages.

Signed-off-by: Gerd Hoffmann <kraxel at redhat.com>
---
 OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf | 1 +
 OvmfPkg/Library/PlatformInitLib/MemDetect.c         | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf b/OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf
index 86a82ad3e084..5a79d95b689c 100644
--- a/OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf
+++ b/OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf
@@ -58,6 +58,7 @@ [LibraryClasses.X64]
 
 [Pcd]
   gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress
+  gEfiMdeModulePkgTokenSpaceGuid.PcdUse1GPageTable
 
 [FixedPcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaBase
diff --git a/OvmfPkg/Library/PlatformInitLib/MemDetect.c b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
index acf90b4e93fd..1102b00ecbf0 100644
--- a/OvmfPkg/Library/PlatformInitLib/MemDetect.c
+++ b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
@@ -663,6 +663,11 @@ PlatformAddressWidthFromCpuid (
       PhysBits = 40;
     }
 
+    if (!FixedPcdGetBool (PcdUse1GPageTable) && (PhysBits > 40)) {
+      DEBUG ((DEBUG_INFO, "%a: limit PhysBits to 40 (PcdUse1GPageTable is false)\n", __func__));
+      PhysBits = 40;
+    }
+
     PlatformInfoHob->PhysMemAddressWidth = PhysBits;
     PlatformInfoHob->FirstNonAddress     = LShiftU64 (1, PlatformInfoHob->PhysMemAddressWidth);
   }
-- 
2.40.1



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