[edk2-devel] [PATCH v3 1/4] OvmfPkg/Sec: Setup MTRR early in the boot process.

["Gerd Hoffmann" <kraxel@redhat.com>]

Specifically before running lzma uncompress of the main firmware volume.
This is needed to make sure caching is enabled, otherwise the uncompress
can be extremely slow.

Adapt the ASSERTs and MTRR setup in PlatformInitLib to the changes.

Background:  Depending on virtual machine configuration kvm may uses EPT
memory types to apply guest MTRR settings.  In case MTRRs are disabled
kvm will use the uncachable memory type for all mappings.  The
vmx_get_mt_mask() function in the linux kernel handles this and can be
found here:

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/arch/x86/kvm/vmx/vmx.c?h=v6.7.1#n7580

In most VM configurations kvm uses MTRR_TYPE_WRBACK unconditionally.  In
case the VM has a mdev device assigned that is not the case though.

Before commit e8aa4c6546ad ("UefiCpuPkg/ResetVector: Cache Disable
should not be set by default in CR0") kvm also ended up using
MTRR_TYPE_WRBACK due to KVM_X86_QUIRK_CD_NW_CLEARED.  After that commit
kvm evaluates guest mtrr settings, which why setting up MTRRs early is
important now.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 OvmfPkg/IntelTdx/Sec/SecMain.c              | 32 +++++++++++++++++++++
 OvmfPkg/Library/PlatformInitLib/MemDetect.c | 10 +++----
 OvmfPkg/Sec/SecMain.c                       | 32 +++++++++++++++++++++
 3 files changed, 69 insertions(+), 5 deletions(-)

diff --git a/OvmfPkg/IntelTdx/Sec/SecMain.c b/OvmfPkg/IntelTdx/Sec/SecMain.c
index 42a587adfa57..a218ca17a01a 100644
--- a/OvmfPkg/IntelTdx/Sec/SecMain.c
+++ b/OvmfPkg/IntelTdx/Sec/SecMain.c
@@ -27,6 +27,8 @@
 #include <Library/TdxHelperLib.h>
 #include <Library/CcProbeLib.h>
 #include <Library/PeilessStartupLib.h>
+#include <Register/Intel/ArchitecturalMsr.h>
+#include <Register/Intel/Cpuid.h>
 
 #define SEC_IDT_ENTRY_COUNT  34
 
@@ -48,6 +50,31 @@ IA32_IDT_GATE_DESCRIPTOR  mIdtEntryTemplate = {
   }
 };
 
+//
+// Enable MTRR early, set default type to write back.
+// Needed to make sure caching is enabled,
+// without this lzma decompress can be very slow.
+//
+STATIC
+VOID
+SecMtrrSetup (
+  VOID
+  )
+{
+  CPUID_VERSION_INFO_EDX           Edx;
+  MSR_IA32_MTRR_DEF_TYPE_REGISTER  DefType;
+
+  AsmCpuid (CPUID_VERSION_INFO, NULL, NULL, NULL, &Edx.Uint32);
+  if (!Edx.Bits.MTRR) {
+    return;
+  }
+
+  DefType.Uint64    = AsmReadMsr64 (MSR_IA32_MTRR_DEF_TYPE);
+  DefType.Bits.Type = 6; /* write back */
+  DefType.Bits.E    = 1; /* enable */
+  AsmWriteMsr64 (MSR_IA32_MTRR_DEF_TYPE, DefType.Uint64);
+}
+
 VOID
 EFIAPI
 SecCoreStartupWithStack (
@@ -204,6 +231,11 @@ SecCoreStartupWithStack (
   InitializeApicTimer (0, MAX_UINT32, TRUE, 5);
   DisableApicTimerInterrupt ();
 
+  //
+  // Initialize MTRR
+  //
+  SecMtrrSetup ();
+
   PeilessStartup (&SecCoreData);
 
   ASSERT (FALSE);
diff --git a/OvmfPkg/Library/PlatformInitLib/MemDetect.c b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
index f042517bb64a..e89f63eee054 100644
--- a/OvmfPkg/Library/PlatformInitLib/MemDetect.c
+++ b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
@@ -1082,18 +1082,18 @@ PlatformQemuInitializeRam (
     MtrrGetAllMtrrs (&MtrrSettings);
 
     //
-    // MTRRs disabled, fixed MTRRs disabled, default type is uncached
+    // See SecMtrrSetup(), default type should be write back
     //
-    ASSERT ((MtrrSettings.MtrrDefType & BIT11) == 0);
+    ASSERT ((MtrrSettings.MtrrDefType & BIT11) != 0);
     ASSERT ((MtrrSettings.MtrrDefType & BIT10) == 0);
-    ASSERT ((MtrrSettings.MtrrDefType & 0xFF) == 0);
+    ASSERT ((MtrrSettings.MtrrDefType & 0xFF) == MTRR_CACHE_WRITE_BACK);
 
     //
     // flip default type to writeback
     //
-    SetMem (&MtrrSettings.Fixed, sizeof MtrrSettings.Fixed, 0x06);
+    SetMem (&MtrrSettings.Fixed, sizeof MtrrSettings.Fixed, MTRR_CACHE_WRITE_BACK);
     ZeroMem (&MtrrSettings.Variables, sizeof MtrrSettings.Variables);
-    MtrrSettings.MtrrDefType |= BIT11 | BIT10 | 6;
+    MtrrSettings.MtrrDefType |= BIT10;
     MtrrSetAllMtrrs (&MtrrSettings);
 
     //
diff --git a/OvmfPkg/Sec/SecMain.c b/OvmfPkg/Sec/SecMain.c
index 31da5d0ace51..46c54f2984ff 100644
--- a/OvmfPkg/Sec/SecMain.c
+++ b/OvmfPkg/Sec/SecMain.c
@@ -30,6 +30,8 @@
 #include <Ppi/MpInitLibDep.h>
 #include <Library/TdxHelperLib.h>
 #include <Library/CcProbeLib.h>
+#include <Register/Intel/ArchitecturalMsr.h>
+#include <Register/Intel/Cpuid.h>
 #include "AmdSev.h"
 
 #define SEC_IDT_ENTRY_COUNT  34
@@ -744,6 +746,31 @@ FindAndReportEntryPoints (
   return;
 }
 
+//
+// Enable MTRR early, set default type to write back.
+// Needed to make sure caching is enabled,
+// without this lzma decompress can be very slow.
+//
+STATIC
+VOID
+SecMtrrSetup (
+  VOID
+  )
+{
+  CPUID_VERSION_INFO_EDX           Edx;
+  MSR_IA32_MTRR_DEF_TYPE_REGISTER  DefType;
+
+  AsmCpuid (CPUID_VERSION_INFO, NULL, NULL, NULL, &Edx.Uint32);
+  if (!Edx.Bits.MTRR) {
+    return;
+  }
+
+  DefType.Uint64    = AsmReadMsr64 (MSR_IA32_MTRR_DEF_TYPE);
+  DefType.Bits.Type = 6; /* write back */
+  DefType.Bits.E    = 1; /* enable */
+  AsmWriteMsr64 (MSR_IA32_MTRR_DEF_TYPE, DefType.Uint64);
+}
+
 VOID
 EFIAPI
 SecCoreStartupWithStack (
@@ -942,6 +969,11 @@ SecCoreStartupWithStack (
   InitializeApicTimer (0, MAX_UINT32, TRUE, 5);
   DisableApicTimerInterrupt ();
 
+  //
+  // Initialize MTRR
+  //
+  SecMtrrSetup ();
+
   //
   // Initialize Debug Agent to support source level debug in SEC/PEI phases before memory ready.
   //
-- 
2.43.0



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