Re: [edk2-devel] [PATCH 3/3] UefiCpuPkg/PiSmmCpu: Enable 5 level paging when CPU supports

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

Laszlo,
I agree with your changes.
Will include your changes in V2.

> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Laszlo Ersek
> Sent: Monday, July 1, 2019 8:45 PM
> To: devel@edk2.groups.io; Ni, Ray <ray.ni@intel.com>
> Cc: Dong, Eric <eric.dong@intel.com>
> Subject: Re: [edk2-devel] [PATCH 3/3] UefiCpuPkg/PiSmmCpu: Enable 5 level
> paging when CPU supports
> 
> On 06/28/19 08:47, Ni, Ray wrote:
> > REF:https://bugzilla.tianocore.org/show_bug.cgi?id=1946
> >
> > The patch changes SMM environment to use 5 level paging when CPU
> > supports it.
> >
> > Signed-off-by: Ray Ni <ray.ni@intel.com>
> > Cc: Eric Dong <eric.dong@intel.com>
> > ---
> >  .../PiSmmCpuDxeSmm/SmmCpuMemoryManagement.c   |  20 +-
> >  UefiCpuPkg/PiSmmCpuDxeSmm/SmmProfile.c        | 272 ++++++----
> >  UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c       | 483 ++++++++++++------
> >  UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm   |  12 +
> >  .../PiSmmCpuDxeSmm/X64/SmmProfileArch.c       |  72 ++-
> >  5 files changed, 559 insertions(+), 300 deletions(-)
> 
> This patch does not build with GCC, because:
> 
> > diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> > index 3d5d663d99..c088010327 100644
> > --- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> > +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> > @@ -16,6 +16,7 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
> >  LIST_ENTRY                          mPagePool = INITIALIZE_LIST_HEAD_VARIABLE
> (mPagePool);
> >  BOOLEAN                             m1GPageTableSupport = FALSE;
> >  BOOLEAN                             mCpuSmmStaticPageTable;
> > +BOOLEAN                             m5LevelPagingSupport;
> 
> as-is, two translation units *define* (allocate) "m5LevelPagingSupport":
> "PageTbl.c" above, and "SmiEntry.nasm". And that breaks the build with
> GCC (it should break the build with VS as well, because it is a bug in
> the code).
> 
> However, I'm not suggesting that we add "extern" to "PageTbl.c".
> 
> Because, I don't think we should reintroduce DBs into the PiSmmCpuDxeSmm
> assembly code. That would be a regression for:
> 
>   https://bugzilla.tianocore.org/show_bug.cgi?id=866
> 
> We should *especially* not reintroduce the dual use of a byte
> - both for binary instruction encoding,
> - and as a data value (for steering C-language code).
> 
> PiSmmCpuDxeSmm had that kind of code before, but I eliminated it. For
> example, in commit 3c5ce64f23c4 ("UefiCpuPkg/PiSmmCpuDxeSmm: patch
> "XdSupported" with PatchInstructionX86()", 2018-04-04).
> 
> Therefore, please incorporate the following update, into patch #3:
> 
> > diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm
> b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm
> > index b5e0405b3b00..ae79bf024bf0 100644
> > --- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm
> > +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm
> > @@ -69,7 +69,7 @@ extern ASM_PFX(mXdSupported)
> >  global ASM_PFX(gPatchXdSupported)
> >  global ASM_PFX(gPatchSmiStack)
> >  global ASM_PFX(gPatchSmiCr3)
> > -global ASM_PFX(m5LevelPagingSupport)
> > +global ASM_PFX(gPatch5LevelPagingSupport)
> >  global ASM_PFX(gcSmiHandlerTemplate)
> >  global ASM_PFX(gcSmiHandlerSize)
> >
> > @@ -126,8 +126,8 @@ ASM_PFX(gPatchSmiCr3):
> >      mov     cr3, rax
> >      mov     eax, 0x668                   ; as cr4.PGE is not set here, refresh cr3
> >
> > -    DB      0xb1                        ; mov cl, m5LevelPagingSupport
> > -ASM_PFX(m5LevelPagingSupport): DB 0
> > +    mov     cl, strict byte 0           ; source operand will be patched
> > +ASM_PFX(gPatch5LevelPagingSupport):
> >      cmp     cl, 0
> >      je      SkipEnable5LevelPaging
> >      ;
> > diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> > index c08801032766..c31160735a37 100644
> > --- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> > +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> > @@ -17,6 +17,7 @@ LIST_ENTRY                          mPagePool =
> INITIALIZE_LIST_HEAD_VARIABLE (m
> >  BOOLEAN                             m1GPageTableSupport = FALSE;
> >  BOOLEAN                             mCpuSmmStaticPageTable;
> >  BOOLEAN                             m5LevelPagingSupport;
> > +X86_ASSEMBLY_PATCH_LABEL            gPatch5LevelPagingSupport;
> >
> >  /**
> >    Disable CET.
> > @@ -337,6 +338,7 @@ SmmInitPageTable (
> >    m1GPageTableSupport    = Is1GPageSupport ();
> >    m5LevelPagingSupport   = Is5LevelPagingSupport ();
> >    mPhysicalAddressBits   = CalculateMaximumSupportAddress ();
> > +  PatchInstructionX86 (gPatch5LevelPagingSupport, m5LevelPagingSupport, 1);
> >    DEBUG ((DEBUG_INFO, "5LevelPaging Support     - %d\n",
> m5LevelPagingSupport));
> >    DEBUG ((DEBUG_INFO, "1GPageTable Support      - %d\n",
> m1GPageTableSupport));
> >    DEBUG ((DEBUG_INFO, "PcdCpuSmmStaticPageTable - %d\n",
> mCpuSmmStaticPageTable));
> 
> With this update, the build succeeds, and a quick regression-test has
> passed for me (using OVMF/IA32X64).
> 
> I'll try to do deeper testing if you agree with this update.
> 
> Thanks,
> Laszlo
> 
>