Laszlo, I tried to design this PCD so it could be used for other architectures as needed in the future by expanding the enum. I marked enum values 0x01(LFENCE) and 0x02(CPUID) for IA32/X64. Value 0x00 (NOP) is for all archs.
Mike > -----Original Message----- > From: devel@edk2.groups.io > [mailto:devel@edk2.groups.io] On Behalf Of Laszlo Ersek > Sent: Tuesday, April 30, 2019 4:47 AM > To: devel@edk2.groups.io; Kinney, Michael D > <michael.d.kin...@intel.com> > Cc: Gao, Liming <liming....@intel.com> > Subject: Re: [edk2-devel] [Patch V2 1/6] MdePkg: Add > PcdSpeculationBarrierType > > On 04/30/19 03:30, Michael D Kinney wrote: > > Add > gEfiMdePkgTokenSpaceGuid.PcdSpeculationBarrierType that > > uses the PCD type FixedAtBuild. This performs a > build time > > selection for the type of speculation barrier to use > in the > > BaseLib function SpeculationBarrier(). The > recommended > > speculation barrier for x86 is LFENCE and this is the > default > > value for this PCD. x86 CPUs that do not support > LFENCE must > > select one of the other supported values which > includes CPUID > > and nothing. > > > > Cc: Liming Gao <liming....@intel.com> > > Signed-off-by: Michael D Kinney > <michael.d.kin...@intel.com> > > --- > > MdePkg/MdePkg.dec | 9 +++++++++ > > MdePkg/MdePkg.uni | 8 ++++++++ > > 2 files changed, 17 insertions(+) > > > > diff --git a/MdePkg/MdePkg.dec b/MdePkg/MdePkg.dec > > index e2ea8fff66..28d4a966c2 100644 > > --- a/MdePkg/MdePkg.dec > > +++ b/MdePkg/MdePkg.dec > > @@ -2062,6 +2062,15 @@ [PcdsFixedAtBuild] > > # @Prompt Enable control flow enforcement. > > > gEfiMdePkgTokenSpaceGuid.PcdControlFlowEnforcementPrope > rtyMask|0x0|UINT32|0x30001017 > > > > + ## Indicates the type of instruction sequence to > use for a speculation > > + # barrier. The default instruction sequence is > LFENCE.<BR><BR> > > + # 0x00 - No operation.<BR> > > + # 0x01 - LFENCE (IA32/X64).<BR> > > + # 0x02 - CPUID (IA32/X64).<BR> > > + # Other - reserved > > + # @Prompt Speculation Barrier Type. > > + > gEfiMdePkgTokenSpaceGuid.PcdSpeculationBarrierType|0x01 > |UINT8|0x30001018 > > + > > [PcdsFixedAtBuild,PcdsPatchableInModule] > > ## Indicates the maximum length of unicode string > used in the following > > # BaseLib functions: StrLen(), StrSize(), > StrCmp(), StrnCmp(), StrCpy(), StrnCpy()<BR><BR> > > In MdePkg.dec, we have: > - [Includes.X64] > - [LibraryClasses.X64] > - [Guids.X64] > > but no PCD declarations that are architecture-specific. > Is that > intentional? Because, this PCD could be a good > candidate for "IA32/X64 > only". (Looking at the next patch too.) > > But, that's just my curiosity. > > Reviewed-by: Laszlo Ersek <ler...@redhat.com> > > Thanks > Laszlo > > > > diff --git a/MdePkg/MdePkg.uni b/MdePkg/MdePkg.uni > > index c359bb4b5b..5c1fa24065 100644 > > --- a/MdePkg/MdePkg.uni > > +++ b/MdePkg/MdePkg.uni > > @@ -149,6 +149,14 @@ > > > " BIT0 - SMM CET Shadow Stack is enabled.<BR>\n" > > > " Other - reserved" > > > > +#string > STR_gEfiMdePkgTokenSpaceGuid_PcdSpeculationBarrierType_ > PROMPT #language en-US "Speculation Barrier Type." > > + > > +#string > STR_gEfiMdePkgTokenSpaceGuid_PcdSpeculationBarrierType_ > HELP #language en-US "Indicates the type of > instruction sequence to use for a speculation.barrier. > The default instruction sequence is LFENCE.<BR><BR>\n" > > + > "0x00 - No operation.<BR>\n" > > + > "0x01 - LFENCE (IA32/X64).<BR>\n" > > + > "0x02 - CPUID (IA32/X64).<BR>\n" > > + > "Other - reserved" > > + > > #string > STR_gEfiMdePkgTokenSpaceGuid_PcdMaximumAsciiStringLengt > h_PROMPT #language en-US "Maximum Length of Ascii > String" > > > > #string > STR_gEfiMdePkgTokenSpaceGuid_PcdMaximumAsciiStringLengt > h_HELP #language en-US "Sets the maximum number of > ASCII characters used for string functions. This > affects the following BaseLib functions: AsciiStrLen(), > AsciiStrSize(), AsciiStrCmp(), AsciiStrnCmp(), > AsciiStrCpy(), AsciiStrnCpy(). <BR><BR>\n" > > > > > -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#39853): https://edk2.groups.io/g/devel/message/39853 Mute This Topic: https://groups.io/mt/31415900/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
