OvmfPkg/SmmAccess: close and lock SMRAM at default SMBASE

During normal boot, when EFI_DXE_SMM_READY_TO_LOCK_PROTOCOL is installed
by platform BDS, the SMM IPL locks SMRAM (TSEG) through
EFI_SMM_ACCESS2_PROTOCOL.Lock(). See SmmIplReadyToLockEventNotify() in
"MdeModulePkg/Core/PiSmmCore/PiSmmIpl.c".

During S3 resume, S3Resume2Pei locks SMRAM (TSEG) through
PEI_SMM_ACCESS_PPI.Lock(), before executing the boot script. See
S3ResumeExecuteBootScript() in
"UefiCpuPkg/Universal/Acpi/S3Resume2Pei/S3Resume.c".

Those are precisely the places where the SMRAM at the default SMBASE
should be locked too. Add such an action to SmramAccessLock().

Notes:

- The SMRAM at the default SMBASE doesn't support the "closed and
  unlocked" state (and so it can't be closed without locking it, and it
  cannot be opened after closing it).

- The SMRAM at the default SMBASE isn't (and shouldn't) be exposed with
  another EFI_SMRAM_DESCRIPTOR in the GetCapabilities() members of
  EFI_SMM_ACCESS2_PROTOCOL / PEI_SMM_ACCESS_PPI. That's because the SMRAM
  in question is not "general purpose"; it's only QEMU's solution to
  protect the initial SMI handler from the OS, when a VCPU is hot-plugged.

  Consequently, the state of the SMRAM at the default SMBASE is not
  reflected in the "OpenState" / "LockState" fields of the protocol and
  PPI.

- An alternative to extending SmramAccessLock() would be to register an
  EFI_DXE_SMM_READY_TO_LOCK_PROTOCOL notify in SmmAccess2Dxe (for locking
  at normal boot), and an EDKII_S3_SMM_INIT_DONE_GUID PPI notify in
  SmmAccessPei (for locking at S3 resume).

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1512
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Message-Id: <20200129214412.2361-10-lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/OvmfPkg/SmmAccess/SmramInternal.h b/OvmfPkg/SmmAccess/SmramInternal.h
index 74d962b4ec..a4d8827adf 100644
--- a/OvmfPkg/SmmAccess/SmramInternal.h
+++ b/OvmfPkg/SmmAccess/SmramInternal.h
@@ -39,6 +39,14 @@ InitQ35TsegMbytes (
   );

 

 /**

+  Save PcdQ35SmramAtDefaultSmbase into mQ35SmramAtDefaultSmbase.

+**/

+VOID

+InitQ35SmramAtDefaultSmbase (

+  VOID

+  );

+

+/**

   Read the MCH_SMRAM and ESMRAMC registers, and update the LockState and

   OpenState fields in the PEI_SMM_ACCESS_PPI / EFI_SMM_ACCESS2_PROTOCOL object,

   from the D_LCK and T_EN bits.