[edk2-devel] [PATCH v2 2/2] UefiCpuPkg/CpuMpPei: Don't write CR3 in ConvertMemoryPageToNotPresent

["Zhiguang Liu" <zhiguang.liu@intel.com>]

The purpose of writing CR3 in ConvertMemoryPageToNotPresent is just
to flush TLB, because CR3 won't be changed in function
ConvertMemoryPageToNotPresent.
After ConvertMemoryPageToNotPresent, there is always a flush TLB
function. Also, because ConvertMemoryPageToNotPresent in called in a
loop, to improve performance, there is no need to flush TLB
inside ConvertMemoryPageToNotPresent. Just flushing TLB after the loop
is enough.

Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Zhiguang Liu <zhiguang.liu@intel.com>
---
 UefiCpuPkg/CpuMpPei/CpuPaging.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/UefiCpuPkg/CpuMpPei/CpuPaging.c b/UefiCpuPkg/CpuMpPei/CpuPaging.c
index 15c7015fb8..b923d9b502 100644
--- a/UefiCpuPkg/CpuMpPei/CpuPaging.c
+++ b/UefiCpuPkg/CpuMpPei/CpuPaging.c
@@ -76,7 +76,8 @@ AllocatePageTableMemory (
 
 /**
   This function modifies the page attributes for the memory region specified
-  by BaseAddress and Length to not present.
+  by BaseAddress and Length to not present. This function only change page
+  table, but not flush TLB. Caller have the responsbility to flush TLB.
 
   Caller should make sure BaseAddress and Length is at page boundary.
 
@@ -167,7 +168,6 @@ ConvertMemoryPageToNotPresent (
   }
 
   ASSERT_EFI_ERROR (Status);
-  AsmWriteCr3 (PageTable);
   return Status;
 }
 
-- 
2.31.1.windows.1



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