[RFC PATCH v2 18/44] OvmfPkg/Sec: Enable cache early to speed up booting

["Lendacky, Thomas" <thomas.lendacky@amd.com>]

From: Tom Lendacky <thomas.lendacky@amd.com>

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198

Currently, the OVMF code relies on the hypervisor to enable the cache
support on the processor in order to improve the boot speed. However,
with SEV-ES, the hypervisor is not allowed to change the CR0 register
to enable caching.

Update the OVMF Sec support to enable caching in order to improve the
boot speed when running as an SEV-ES guest.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 OvmfPkg/Sec/SecMain.inf |  1 +
 OvmfPkg/Sec/SecMain.c   | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/OvmfPkg/Sec/SecMain.inf b/OvmfPkg/Sec/SecMain.inf
index 7f53845f5436..fdf00e5d8be3 100644
--- a/OvmfPkg/Sec/SecMain.inf
+++ b/OvmfPkg/Sec/SecMain.inf
@@ -51,6 +51,7 @@ [LibraryClasses]
   ExtractGuidedSectionLib
   LocalApicLib
   CpuExceptionHandlerLib
+  MemEncryptSevLib
 
 [Ppis]
   gEfiTemporaryRamSupportPpiGuid                # PPI ALWAYS_PRODUCED
diff --git a/OvmfPkg/Sec/SecMain.c b/OvmfPkg/Sec/SecMain.c
index 7f1dfb2e57c1..20716d484ab0 100644
--- a/OvmfPkg/Sec/SecMain.c
+++ b/OvmfPkg/Sec/SecMain.c
@@ -25,6 +25,7 @@
 #include <Library/ExtractGuidedSectionLib.h>
 #include <Library/LocalApicLib.h>
 #include <Library/CpuExceptionHandlerLib.h>
+#include <Library/MemEncryptSevLib.h>
 
 #include <Ppi/TemporaryRamSupport.h>
 
@@ -755,6 +756,15 @@ SecCoreStartupWithStack (
 
   ProcessLibraryConstructorList (NULL, NULL);
 
+  //
+  // Under SEV-ES, the hypervisor can't modify CR0 and so can't enable
+  // caching in order to speed up the boot. Enable caching early for
+  // an SEV-ES guest.
+  //
+  if (MemEncryptSevEsIsEnabled()) {
+    AsmEnableCache ();
+  }
+
   DEBUG ((EFI_D_INFO,
     "SecCoreStartupWithStack(0x%x, 0x%x)\n",
     (UINT32)(UINTN)BootFv,
-- 
2.17.1