Customer met system hang-up during serial port loopback test in OS.
It is a corner case happened with one CPU core doing "out dx,al" and
another CPU core(s) doing "rep outs dx,byte ptr [rsi]".
Detailed code flow is as below.
1. Serial port loopback test in OS.
One CPU core: "out dx,al" -> Writing B2h, SMI will happen.
Another CPU core(s): "rep outs dx,byte ptr [rsi]".
2. SMI happens to enter SMM.
"out dx" (SMM_IO_TYPE_OUT_DX) is saved as I/O instruction type in
SMRAM save state for CPU doing "out dx,al".
"rep outs dx" (SMM_IO_TYPE_REP_OUTS) is saved as I/O instruction
type and rsi is save as I/O Memory Address in SMRAM save state for
CPU doing "rep outs dx, byte ptr [rsi]".
NOTE: I/O Memory Address (rsi) is a virtual address mapped by
OS/Virtual Machine.
3. Some SMM code calls EFI_SMM_CPU_PROTOCOL.ReadSaveState() with
EFI_SMM_SAVE_STATE_REGISTER_IO and parse data returned.
For example:
https://github.com/tianocore/edk2/blob/master/QuarkSocPkg/
QuarkNorthCluster/Smm/DxeSmm/QncSmmDispatcher/QNC/QNCSmmSw.c#L76
4. SmmReadSaveState() is executed to read save state for
EFI_SMM_SAVE_STATE_REGISTER_IO.
- The SmmReadSaveState() function in
"UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c" calls the
SmmCpuFeaturesReadSaveStateRegister() function, from the platform's
SmmCpuFeaturesLib instance.
- If that platform-specific function returns EFI_UNSUPPORTED, then
PiSmmCpuDxeSmm falls back to the common function
ReadSaveStateRegister(), defined in file
"UefiCpuPkg/PiSmmCpuDxeSmm/SmramSaveState.c".
Current ReadSaveStateRegister() in
UefiCpuPkg/PiSmmCpuDxeSmm/SmramSaveState.c is trying to copy data
from I/O Memory Address for EFI_SMM_SAVE_STATE_IO_TYPE_REP_PREFIX,
PF will happen as SMM page table does not know and cover this
OS/Virtual Machine virtual address.
Same case is for SmmCpuFeaturesReadSaveStateRegister() in platform-
specific SmmCpuFeaturesLib instance if it has similar implementation
to read save state for EFI_SMM_SAVE_STATE_REGISTER_IO with
EFI_SMM_SAVE_STATE_IO_TYPE_REP_PREFIX.
Same case is for "ins", 'outs' and 'rep ins'.
So to fix the problem, this patch updates the code to only support
IN/OUT, but not INS/OUTS/REP INS/REP OUTS for SmmReadSaveState().
Cc: Eric Dong <eric.dong@intel.com> Cc: Ray Ni <ray.ni@intel.com> Cc: Laszlo Ersek <lersek@redhat.com> Signed-off-by: Star Zeng <star.zeng@intel.com> Reviewed-by: Laszlo Ersek <lersek@redhat.com>