Hi Nate, The 'PcdCpuSmmStaticPageTable' is only used in the X64 version of PageTbl.c that's why I updated only for 64 bit. SMM always builds static page table for IA32. Please refer my previous mail for more details.
Thanks, Narendra > -----Original Message----- > From: Desimone, Nathaniel L > Sent: Tuesday, April 2, 2019 5:57 AM > To: Vanguput, Narendra K <narendra.k.vangu...@intel.com>; edk2- > de...@lists.01.org > Cc: Yao, Jiewen <jiewen....@intel.com>; Dong, Eric <eric.d...@intel.com>; > Laszlo Ersek <ler...@redhat.com> > Subject: RE: [edk2] [PATCH v9] UefiCpuPkg\CpuSmm: Save & restore CR2 on- > demand paging in SMM > > This patch seems to only add the IN/OUT decorators on function parameters, > which is a good change. However, it does not address any of my previous > comments: > > 1. Why would you do this for 64 bit but not 32 bit? > 2. Why don't you add the if statement to MpService.c instead of spreading it > to PageTbl.c? > 3. What is the reason for this anyway? Adding the conditional is probably > more execution time than just reading CR2 always. > > I also share Andrew's concern that in the case of a periodic SMI happening > during OS runtime, there is nothing preventing the handler of the periodic > SMI from clobbering the value of CR2, which could potentially cause kernel > panics once we return back from SMM to the OS. I am not aware of any > periodic SMIs in OVMF, so I don't believe OVMF testing will catch these type > of issues. I consider not doing the save/restore in the 32 bit SMM to be > dangerous, especially since all recent platforms that I can think of don't > use 32 > bit SMM anymore, so any bug(s) introduced may go unnoticed for a long time. > > Thanks, > Nate > > -----Original Message----- > From: edk2-devel <edk2-devel-boun...@lists.01.org> On Behalf Of nkvangup > Sent: Monday, April 1, 2019 1:16 AM > To: edk2-devel@lists.01.org > Cc: Yao, Jiewen <jiewen....@intel.com>; Dong, Eric <eric.d...@intel.com>; > Laszlo Ersek <ler...@redhat.com> > Subject: [edk2] [PATCH v9] UefiCpuPkg\CpuSmm: Save & restore CR2 on- > demand paging in SMM > > BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=1593 > > For every SMI occurrence, save and restore CR2 register only when SMM on- > demand paging support is enabled in 64 bit operation mode. > This is not a bug but to have better improvement of code. > > Patch5 is updated with separate functions for Save and Restore of CR2 based > on review feedback. > > Patch6 - Removed Global Cr2 instead used function parameter. > > Patch7 - Removed checking Cr2 with 0 as per feedback. > > Patch8 and 9 - Aligned with EDK2 Coding style. > > Contributed-under: TianoCore Contribution Agreement 1.1 > Signed-off-by: Vanguput Narendra K <narendra.k.vangu...@intel.com> > Cc: Eric Dong <eric.d...@intel.com> > Cc: Ray Ni <ray...@intel.com> > Cc: Laszlo Ersek <ler...@redhat.com> > Cc: Yao Jiewen <jiewen....@intel.com> > --- > UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c | 26 > ++++++++++++++++++++++++++ > UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c | 9 ++++++--- > UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h | 22 > ++++++++++++++++++++++ > UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c | 30 > ++++++++++++++++++++++++++++++ > 4 files changed, 84 insertions(+), 3 deletions(-) > > diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c > b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c > index b734a1ea8c..d1e146a70c 100644 > --- a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c > +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c > @@ -316,3 +316,29 @@ SetPageTableAttributes ( > > return ; > } > + > +/** > + This function returns with no action for 32 bit. > + > + @param[out] *Cr2 Pointer to variable to hold CR2 register value. > +**/ > +VOID > +SaveCr2 ( > + OUT UINTN *Cr2 > + ) > +{ > + return ; > +} > + > +/** > + This function returns with no action for 32 bit. > + > + @param[in] Cr2 Value to write into CR2 register. > +**/ > +VOID > +RestoreCr2 ( > + IN UINTN Cr2 > + ) > +{ > + return ; > +} > diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c > b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c > index 3b0b3b52ac..ce70f77709 100644 > --- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c > +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c > @@ -1112,9 +1112,11 @@ SmiRendezvous ( > ASSERT(CpuIndex < mMaxNumberOfCpus); > > // > - // Save Cr2 because Page Fault exception in SMM may override its value > + // Save Cr2 because Page Fault exception in SMM may override its > + value, // when using on-demand paging for above 4G memory. > // > - Cr2 = AsmReadCr2 (); > + Cr2 = 0; > + SaveCr2 (&Cr2); > > // > // Perform CPU specific entry hooks > @@ -1253,10 +1255,11 @@ SmiRendezvous ( > > Exit: > SmmCpuFeaturesRendezvousExit (CpuIndex); > + > // > // Restore Cr2 > // > - AsmWriteCr2 (Cr2); > + RestoreCr2 (Cr2); > } > > /** > diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h > b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h > index 84efb22981..38f9104117 100644 > --- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h > +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h > @@ -1243,4 +1243,26 @@ EFIAPI > PiSmmCpuSmiEntryFixupAddress ( > ); > > +/** > + This function reads CR2 register when on-demand paging is enabled > + for 64 bit and no action for 32 bit. > + > + @param[out] *Cr2 Pointer to variable to hold CR2 register value. > +**/ > +VOID > +SaveCr2 ( > + OUT UINTN *Cr2 > + ); > + > +/** > + This function writes into CR2 register when on-demand paging is > +enabled > + for 64 bit and no action for 32 bit. > + > + @param[in] Cr2 Value to write into CR2 register. > +**/ > +VOID > +RestoreCr2 ( > + IN UINTN Cr2 > + ); > + > #endif > diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c > b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c > index 2c77cb47a4..95eaf0b016 100644 > --- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c > +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c > @@ -1053,3 +1053,33 @@ SetPageTableAttributes ( > > return ; > } > + > +/** > + This function reads CR2 register when on-demand paging is enabled. > + > + @param[out] *Cr2 Pointer to variable to hold CR2 register value. > +**/ > +VOID > +SaveCr2 ( > + OUT UINTN *Cr2 > + ) > +{ > + if (!mCpuSmmStaticPageTable) { > + *Cr2 = AsmReadCr2 (); > + } > +} > + > +/** > + This function restores CR2 register when on-demand paging is enabled. > + > + @param[in] Cr2 Value to write into CR2 register. > +**/ > +VOID > +RestoreCr2 ( > + IN UINTN Cr2 > + ) > +{ > + if (!mCpuSmmStaticPageTable) { > + AsmWriteCr2 (Cr2); > + } > +} > -- > 2.16.2.windows.1 > > _______________________________________________ > edk2-devel mailing list > edk2-devel@lists.01.org > https://lists.01.org/mailman/listinfo/edk2-devel _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
