Re: [edk2-devel] [Patch V2 2/6] MdePkg/BaseLib: Use PcdSpeculationBarrierType

["Michael D Kinney" <michael.d.kinney@intel.com>]

Laszlo,

I agree the current usage is only for IA32/X64 source
files so your suggestion make sense.  If there is
a use case for other archs in the future for this PCD,
then the INF would have to be updated.

Mike

> -----Original Message-----
> From: Laszlo Ersek [mailto:lersek@redhat.com]
> Sent: Tuesday, April 30, 2019 4:50 AM
> To: devel@edk2.groups.io; Kinney, Michael D
> <michael.d.kinney@intel.com>
> Cc: Gao, Liming <liming.gao@intel.com>
> Subject: Re: [edk2-devel] [Patch V2 2/6]
> MdePkg/BaseLib: Use PcdSpeculationBarrierType
> 
> On 04/30/19 03:30, Michael D Kinney wrote:
> > Use PcdSpeculationBarrierType in the x86
> implementation
> > of SpeculationBarrier() to select between
> AsmLfence(),
> > AsmCpuid(), and no operation.
> >
> > Cc: Liming Gao <liming.gao@intel.com>
> > Signed-off-by: Michael D Kinney
> <michael.d.kinney@intel.com>
> > ---
> >  MdePkg/Library/BaseLib/BaseLib.inf             | 1 +
> >  MdePkg/Library/BaseLib/X86SpeculationBarrier.c | 8
> ++++++--
> >  2 files changed, 7 insertions(+), 2 deletions(-)
> >
> > diff --git a/MdePkg/Library/BaseLib/BaseLib.inf
> b/MdePkg/Library/BaseLib/BaseLib.inf
> > index 533e83e0b2..3586beb0ab 100644
> > --- a/MdePkg/Library/BaseLib/BaseLib.inf
> > +++ b/MdePkg/Library/BaseLib/BaseLib.inf
> > @@ -394,6 +394,7 @@ [Pcd]
> >
> gEfiMdePkgTokenSpaceGuid.PcdMaximumAsciiStringLength
> ## SOMETIMES_CONSUMES
> >
> gEfiMdePkgTokenSpaceGuid.PcdMaximumUnicodeStringLength
> ## SOMETIMES_CONSUMES
> >
> gEfiMdePkgTokenSpaceGuid.PcdControlFlowEnforcementPrope
> rtyMask   ## SOMETIMES_CONSUMES
> > +  gEfiMdePkgTokenSpaceGuid.PcdSpeculationBarrierType
> ## SOMETIMES_CONSUMES
> >
> >  [FeaturePcd]
> >    gEfiMdePkgTokenSpaceGuid.PcdVerifyNodeInList  ##
> CONSUMES
> 
> So, based on the example of
> 
> 
> MdePkg/Library/SecPeiDxeTimerLibCpu/SecPeiDxeTimerLibCp
> u.inf
> 
> and a few other INF files, I think we could use
> 
>   [Pcd.IA32, Pcd.X64]
> 
> here as well.
> 
> Just an idea.
> 
> Reviewed-by: Laszlo Ersek <lersek@redhat.com>
> 
> Thanks
> Laszlo
> 
> > diff --git
> a/MdePkg/Library/BaseLib/X86SpeculationBarrier.c
> b/MdePkg/Library/BaseLib/X86SpeculationBarrier.c
> > index 8e5f983bb8..b28fd8de9b 100644
> > --- a/MdePkg/Library/BaseLib/X86SpeculationBarrier.c
> > +++ b/MdePkg/Library/BaseLib/X86SpeculationBarrier.c
> > @@ -1,7 +1,7 @@
> >  /** @file
> >    SpeculationBarrier() function for IA32 and x64.
> >
> > -  Copyright (C) 2018, Intel Corporation. All rights
> reserved.<BR>
> > +  Copyright (C) 2018 - 2019, Intel Corporation. All
> rights reserved.<BR>
> >
> >    SPDX-License-Identifier: BSD-2-Clause-Patent
> >
> > @@ -22,5 +22,9 @@ SpeculationBarrier (
> >    VOID
> >    )
> >  {
> > -  AsmLfence ();
> > +  if (PcdGet8 (PcdSpeculationBarrierType) == 0x01) {
> > +    AsmLfence ();
> > +  } else if (PcdGet8 (PcdSpeculationBarrierType) ==
> 0x02) {
> > +    AsmCpuid (0x01, NULL, NULL, NULL, NULL);
> > +  }
> >  }
> >