UefiCpuPkg/MpInitLib: Fix MemTest86 failure.

V2 changes: Update the commit message and comments in the code. When waking vector buffer allocated by CpuDxe is tested by MemTest86 in MP mode, an error is reported because the same range of memory is modified by both CpuDxe driver and MemTest86. The waking vector buffer is not expected to be tested by MemTest86 if it is allocated out because MemTest86 only tests free memory. But current CpuDxe driver "borrows" buffer instead of allocate buffer for waking vector buffer (through allocate & free to get the buffer pointer, backup the buffer data before using it and restore it after using). With this implementation, if the buffer borrowed is not used by any other drivers, MemTest86 tool will treat it as free memory and test it. In order to fix the above issue, CpuDxe changes to allocate the buffer below 1M instead of borrowing it. But directly allocating memory below 1MB causes LegacyBios driver fails to start. LegacyBios driver allocates memory range from "0xA0000 - PcdEbdaReservedMemorySize" to 0xA0000 as Ebda Reserved Memory. The minimum value for "0xA0000 - PcdEbdaReservedMemorySize" is 0x88000. If LegacyBios driver allocate this range failed, it asserts. LegacyBios also reserves range from 0x60000 to "0x60000 + PcdOpromReservedMemorySize", it will be used as Oprom Reserve Memory. The maximum value for "0x60000 + PcdOpromReservedMemorySize" is 0x88000. LegacyBios driver tries to allocate these range page(4K size) by page. It just reports warning message if some pages are already allocated by others. Base on above investigation, one page in range 0x60000 ~ 0x88000 can be used as the waking vector buffer. LegacyBios driver only reports warning when page allocation in range [0x60000, 0x88000) fails. This library is consumed by CpuDxe driver to produce CPU Arch protocol. LagacyBios driver depends on CPU Arch protocol which guarantees below allocation runs earlier than LegacyBios driver. Cc: Ray Ni <ray.ni@intel.com> Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Eric Dong <eric.dong@intel.com> Reviewed-by: Ray Ni <ray.ni@intel.com>
tianocore · Apr 4, 2019 · e4ff634 · e4ff634
1 parent 7ed7212
commit e4ff634
Showing 1 changed file with 15 additions and 11 deletions.
diff --git a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
@@ -76,7 +76,7 @@ SaveCpuMpData (
 }
 
 /**
-  Get available system memory below 1MB by specified size.
+  Get available system memory below 0x88000 by specified size.
 
   @param[in] WakeupBufferSize   Wakeup buffer size required
 
@@ -91,25 +91,29 @@ GetWakeupBuffer (
   EFI_STATUS              Status;
   EFI_PHYSICAL_ADDRESS    StartAddress;
 
-  StartAddress = BASE_1MB;
+  //
+  // Try to allocate buffer below 1M for waking vector.
+  // LegacyBios driver only reports warning when page allocation in range
+  // [0x60000, 0x88000) fails.
+  // This library is consumed by CpuDxe driver to produce CPU Arch protocol.
+  // LagacyBios driver depends on CPU Arch protocol which guarantees below
+  // allocation runs earlier than LegacyBios driver.
+  //
+  StartAddress = 0x88000;
   Status = gBS->AllocatePages (
                   AllocateMaxAddress,
                   EfiBootServicesData,
                   EFI_SIZE_TO_PAGES (WakeupBufferSize),
                   &StartAddress
                   );
   ASSERT_EFI_ERROR (Status);
-  if (!EFI_ERROR (Status)) {
-    Status = gBS->FreePages(
-               StartAddress,
-               EFI_SIZE_TO_PAGES (WakeupBufferSize)
-               );
-    ASSERT_EFI_ERROR (Status);
-    DEBUG ((DEBUG_INFO, "WakeupBufferStart = %x, WakeupBufferSize = %x\n",
-                        (UINTN) StartAddress, WakeupBufferSize));
-  } else {
+  if (EFI_ERROR (Status)) {
     StartAddress = (EFI_PHYSICAL_ADDRESS) -1;
   }
+
+  DEBUG ((DEBUG_INFO, "WakeupBufferStart = %x, WakeupBufferSize = %x\n",
+                      (UINTN) StartAddress, WakeupBufferSize));
+
   return (UINTN) StartAddress;
 }