[PATCH v6 35/42] OvmfPkg/Sec: Enable cache early to speed up booting

["Lendacky, Thomas" <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>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 OvmfPkg/Sec/SecMain.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/OvmfPkg/Sec/SecMain.c b/OvmfPkg/Sec/SecMain.c
index 1dd185aabc8a..fa66ced816dd 100644
--- a/OvmfPkg/Sec/SecMain.c
+++ b/OvmfPkg/Sec/SecMain.c
@@ -877,6 +877,13 @@ SecCoreStartupWithStack (
     // For non SEV-ES guests, just load the IDTR.
     //
     AsmWriteIdtr (&IdtDescriptor);
+  } else {
+    //
+    // 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.
+    //
+    AsmEnableCache ();
   }
 
   DEBUG ((EFI_D_INFO,
-- 
2.17.1