Re: [edk2-devel] [PATCH 3/4] MdeModulePkg/DxeIpl: Introduce PCD PcdUse5LevelPageTable

["Ni, Ray" <ray.ni@intel.com>]

Hao,
Certain OS loaders may fail to boot when 5-level paging is used. PCD can be used to restrict to 4-level paging.

> -----Original Message-----
> From: Wu, Hao A
> Sent: Tuesday, July 23, 2019 10:06 AM
> To: devel@edk2.groups.io; Ni, Ray <ray.ni@intel.com>
> Cc: Dong, Eric <eric.dong@intel.com>; Laszlo Ersek <lersek@redhat.com>
> Subject: RE: [edk2-devel] [PATCH 3/4] MdeModulePkg/DxeIpl: Introduce PCD PcdUse5LevelPageTable
> 
> > -----Original Message-----
> > From: devel@edk2.groups.io [mailto:devel@edk2.groups.io] On Behalf Of Ni,
> > Ray
> > Sent: Monday, July 22, 2019 4:16 PM
> > To: devel@edk2.groups.io
> > Cc: Dong, Eric; Laszlo Ersek
> > Subject: [edk2-devel] [PATCH 3/4] MdeModulePkg/DxeIpl: Introduce PCD
> > PcdUse5LevelPageTable
> >
> > REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2008
> >
> > The PCD indicates if 5-Level Paging will be enabled in long mode.
> > 5-Level Paging will not be enabled when the PCD is TRUE but CPU
> > doesn't support 5-Level Paging.
> >
> > Signed-off-by: Ray Ni <ray.ni@intel.com>
> > Cc: Eric Dong <eric.dong@intel.com>
> > Cc: Laszlo Ersek <lersek@redhat.com>
> > ---
> >  MdeModulePkg/MdeModulePkg.dec | 7 +++++++
> 
> 
> Hello,
> 
> Please help to add the PCD description string definitions in MdeModulePkg.uni.
> 
> One question, is this PCD introduced for the consideration of memory
> consumption by the page table entries? Or is there any other purpose?
> 
> Best Regards,
> Hao Wu
> 
> 
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/MdeModulePkg/MdeModulePkg.dec
> > b/MdeModulePkg/MdeModulePkg.dec
> > index 12e0bbf579..21388595a9 100644
> > --- a/MdeModulePkg/MdeModulePkg.dec
> > +++ b/MdeModulePkg/MdeModulePkg.dec
> > @@ -1991,6 +1991,13 @@ [PcdsFixedAtBuild, PcdsPatchableInModule,
> > PcdsDynamic, PcdsDynamicEx]
> >    # @Prompt The address mask when memory encryption is enabled.
> >
> > gEfiMdeModulePkgTokenSpaceGuid.PcdPteMemoryEncryptionAddressOrM
> > ask|0x0|UINT64|0x30001047
> >
> > +  ## Indicates if 5-Level Paging will be enabled in long mode. 5-Level Paging
> > will not be enabled
> > +  #  when the PCD is TRUE but CPU doesn't support 5-Level Paging.
> > +  #   TRUE  - 5-Level Paging will be enabled.<BR>
> > +  #   FALSE - 5-Level Paging will not be enabled.<BR>
> > +  # @Prompt Enable 5-Level Paging support in long mode.
> > +
> > gEfiMdeModulePkgTokenSpaceGuid.PcdUse5LevelPageTable|FALSE|BOOLE
> > AN|0x0001105F
> > +
> >    ## Capsule In Ram is to use memory to deliver the capsules that will be
> > processed after system
> >    #  reset.<BR><BR>
> >    #  This PCD indicates if the Capsule In Ram is supported.<BR>
> > --
> > 2.21.0.windows.1
> >
> >
> >