edk2/SOURCES/0030-OvmfPkg-Sec-Setup-MTRR-early-in-the-boot-process.patch

From 4c49c1bcb2db128cc4d2ebb29b1ac53fe3ef6b18 Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Tue, 30 Jan 2024 14:04:38 +0100
Subject: [PATCH] OvmfPkg/Sec: Setup MTRR early in the boot process.

RH-Author: Gerd Hoffmann <None>
RH-MergeRequest: 55: OvmfPkg/Sec: Setup MTRR early in the boot process.
RH-Jira: RHEL-21704
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
RH-Commit: [1/4] c4061788d34f409944898b48642d610c259161f3 (kraxel.rh/centos-src-edk2)

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.

Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-ID: <20240130130441.772484-2-kraxel@redhat.com>

[ kraxel: Downstream-only for now.  Timely upstream merge is unlikely
          due to chinese holidays and rhel-9.4 deadlines are close.
          QE regression testing passed.  So go with upstream posted
          series v3 ]

patch_name: edk2-OvmfPkg-Sec-Setup-MTRR-early-in-the-boot-process.patch
present_in_specfile: true
location_in_specfile: 49
---
 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 4e750755bf..7094d86159 100644
--- a/OvmfPkg/IntelTdx/Sec/SecMain.c
+++ b/OvmfPkg/IntelTdx/Sec/SecMain.c
@@ -26,6 +26,8 @@
 #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
 
@@ -47,6 +49,31 @@ 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 (
@@ -203,6 +230,11 @@ 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 e64c0ee324..b6ba63ef95 100644
--- a/OvmfPkg/Library/PlatformInitLib/MemDetect.c
+++ b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
@@ -1164,18 +1164,18 @@ 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 60dfa61842..725b57e2fa 100644
--- a/OvmfPkg/Sec/SecMain.c
+++ b/OvmfPkg/Sec/SecMain.c
@@ -29,6 +29,8 @@
 #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
@@ -743,6 +745,31 @@ 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.
   //