UefiCpuPkg/CpuDxe: Enable protection for newly added page table

One of the functionalities of CpuDxe is to update memory paging attributes.
If page table protection is applied, it must be disabled temporarily before
any attributes update and enabled again afterwards.

This patch makes use of the same way as DxeIpl to allocate page table memory
from reserved memory pool, which helps to reduce potential "split" operation
and recursive calling of SetMemorySpaceAttributes().

Laszlo (lersek@redhat.com) did a regression test on QEMU virtual platform with
one middle version of this series patch. The details can be found at

 https://lists.01.org/pipermail/edk2-devel/2017-December/018625.html

There're a few changes after his work.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>

1 files changed, 16 insertions, 1 deletions

diff --git a/UefiCpuPkg/CpuDxe/CpuDxe.c b/UefiCpuPkg/CpuDxe/CpuDxe.c
index 8ddebabd02..6ae2dcd1c7 100644
--- a/UefiCpuPkg/CpuDxe/CpuDxe.c
+++ b/UefiCpuPkg/CpuDxe/CpuDxe.c
@@ -25,6 +25,7 @@
 BOOLEAN                   InterruptState = FALSE;

 EFI_HANDLE                mCpuHandle = NULL;

 BOOLEAN                   mIsFlushingGCD;

+BOOLEAN                   mIsAllocatingPageTable = FALSE;

 UINT64                    mValidMtrrAddressMask;

 UINT64                    mValidMtrrBitsMask;

 UINT64                    mTimerPeriod = 0;

@@ -407,6 +408,20 @@ CpuSetMemoryAttributes (
     return EFI_SUCCESS;

   }

 

+  //

+  // During memory attributes updating, new pages may be allocated to setup

+  // smaller granularity of page table. Page allocation action might then cause

+  // another calling of CpuSetMemoryAttributes() recursively, due to memory

+  // protection policy configured (such as PcdDxeNxMemoryProtectionPolicy).

+  // Since this driver will always protect memory used as page table by itself,

+  // there's no need to apply protection policy requested from memory service.

+  // So it's safe to just return EFI_SUCCESS if this time of calling is caused

+  // by page table memory allocation.

+  //

+  if (mIsAllocatingPageTable) {

+    DEBUG((DEBUG_VERBOSE, "  Allocating page table memory\n"));

+    return EFI_SUCCESS;

+  }

 

   CacheAttributes = Attributes & CACHE_ATTRIBUTE_MASK;

   MemoryAttributes = Attributes & MEMORY_ATTRIBUTE_MASK;

@@ -487,7 +502,7 @@ CpuSetMemoryAttributes (
   //

   // Set memory attribute by page table

   //

-  return AssignMemoryPageAttributes (NULL, BaseAddress, Length, MemoryAttributes, AllocatePages);

+  return AssignMemoryPageAttributes (NULL, BaseAddress, Length, MemoryAttributes, NULL);

 }

 

 /**