答复: [edk2] [PATCH] IntelSiliconPkg VTdDxe: a question about the source code

["Jerry Zhou(BJ-RD)" <JerryZhou@zhaoxin.com>]

Hi Star,
         I'am so interested in DMA protection in UEFI. It's a really good design!
         But I have a question about the implemention of DisableDmar() in IntelSiliconPkg\feature\vtd\intelvtddxe\VtdReg.c
         Is it a typing error in the code segment below?

    //
    // Disable VTd
    //
    MmioWrite32 (mVtdUnitInformation[Index].VtdUnitBaseAddress + R_GCMD_REG, B_GMCD_REG_SRTP);
    do {
      Reg32 = MmioRead32 (mVtdUnitInformation[Index].VtdUnitBaseAddress + R_GSTS_REG);
　　} while((Reg32 & B_GSTS_REG_RTPS) == 0);
　　
　　The software should program the B_GMCD_REG_TE field in global command register and then poll the B_GSTS_REG_TE field in global status register if the DMAR is expected to be disabled or enabled according to Vt-d specification.
　　
Thanks
Jerry Zhou
Ext:892418



-----邮件原件-----
发件人: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] 代表 Star Zeng
发送时间: 2018年10月24日 11:32
收件人: edk2-devel@lists.01.org
抄送: Jiewen Yao; Star Zeng
主题: [edk2] [PATCH] IntelSiliconPkg VTdDxe: Option to force no early access attr request

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1272

To have high confidence in usage for platform, add option (BIT2 of
PcdVTdPolicyPropertyMask) to force no IOMMU access attribute request
recording before DMAR table is installed.

Check PcdVTdPolicyPropertyMask BIT2 before RequestAccessAttribute()
and ProcessRequestedAccessAttribute(), then RequestAccessAttribute(),
ProcessRequestedAccessAttribute() and mAccessRequestXXX variables
could be optimized by compiler when PcdVTdPolicyPropertyMask BIT2 = 1.

Test done:
1: Created case that has IOMMU access attribute request before DMAR
   table is installed, ASSERT was triggered after setting
   PcdVTdPolicyPropertyMask BIT2 to 1.

2. Confirmed RequestAccessAttribute(), ProcessRequestedAccessAttribute()
   and mAccessRequestXXX variables were optimized by compiler after
   setting PcdVTdPolicyPropertyMask BIT2 to 1.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Rangasai V Chaganty <rangasai.v.chaganty@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Star Zeng <star.zeng@intel.com>
---
IntelSiliconPkg/Feature/VTd/IntelVTdDxe/DmaProtection.c | 8 +++++++-
IntelSiliconPkg/Feature/VTd/IntelVTdDxe/IntelVTdDxe.c   | 7 +++++++
IntelSiliconPkg/IntelSiliconPkg.dec                     | 1 +
3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/DmaProtection.c b/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/DmaProtection.c
index 86d50eb6f288..7784545631b3 100644
--- a/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/DmaProtection.c
+++ b/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/DmaProtection.c
@@ -515,7 +515,13 @@ SetupVtd (

   ParseDmarAcpiTableRmrr ();

-  ProcessRequestedAccessAttribute ();
+  if ((PcdGet8 (PcdVTdPolicyPropertyMask) & BIT2) == 0) {
+    //
+    // Support IOMMU access attribute request recording before DMAR table is installed.
+    // Here is to process the requests.
+    //
+    ProcessRequestedAccessAttribute ();
+  }

   for (Index = 0; Index < mVtdUnitNumber; Index++) {
     DEBUG ((DEBUG_INFO,"VTD Unit %d (Segment: %04x)\n", Index, mVtdUnitInformation[Index].Segment));
diff --git a/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/IntelVTdDxe.c b/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/IntelVTdDxe.c
index 25d7c80af1d4..09948ce50e94 100644
--- a/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/IntelVTdDxe.c
+++ b/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/IntelVTdDxe.c
@@ -254,6 +254,13 @@ VTdSetAttribute (
     // Record the entry to driver global variable.
     // As such once VTd is activated, the setting can be adopted.
     //
+    if ((PcdGet8 (PcdVTdPolicyPropertyMask) & BIT2) != 0) {
+      //
+      // Force no IOMMU access attribute request recording before DMAR table is installed.
+      //
+      ASSERT_EFI_ERROR (EFI_NOT_READY);
+      return EFI_NOT_READY;
+    }
     Status = RequestAccessAttribute (Segment, SourceId, DeviceAddress, Length, IoMmuAccess);
   } else {
     PERF_CODE (
diff --git a/IntelSiliconPkg/IntelSiliconPkg.dec b/IntelSiliconPkg/IntelSiliconPkg.dec
index b9646d773b95..900e8f63c64d 100644
--- a/IntelSiliconPkg/IntelSiliconPkg.dec
+++ b/IntelSiliconPkg/IntelSiliconPkg.dec
@@ -64,6 +64,7 @@ [PcdsFixedAtBuild, PcdsPatchableInModule, PcdsDynamic, PcdsDynamicEx]
   ## The mask is used to control VTd behavior.<BR><BR>
   #  BIT0: Enable IOMMU during boot (If DMAR table is installed in DXE. If VTD_INFO_PPI is installed in PEI.)
   #  BIT1: Enable IOMMU when transfer control to OS (ExitBootService in normal boot. EndOfPEI in S3)
+  #  BIT2: Force no IOMMU access attribute request recording before DMAR table is installed.
   # @Prompt The policy for VTd driver behavior.
   gIntelSiliconPkgTokenSpaceGuid.PcdVTdPolicyPropertyMask|1|UINT8|0x00000002

--
2.7.0.windows.1

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