Reviewed-by: Eric Dong <eric.d...@intel.com> > -----Original Message----- > From: Tom Lendacky <thomas.lenda...@amd.com> > Sent: Friday, June 5, 2020 9:28 PM > To: devel@edk2.groups.io > Cc: Brijesh Singh <brijesh.si...@amd.com>; Ard Biesheuvel > <ard.biesheu...@arm.com>; Dong, Eric <eric.d...@intel.com>; Justen, > Jordan L <jordan.l.jus...@intel.com>; Laszlo Ersek <ler...@redhat.com>; > Gao, Liming <liming....@intel.com>; Kinney, Michael D > <michael.d.kin...@intel.com>; Ni, Ray <ray...@intel.com> > Subject: [PATCH v9 40/46] UefiCpuPkg: Add a 16-bit protected mode code > segment descriptor > > BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198 > > A hypervisor is not allowed to update an SEV-ES guests register state, so > when booting an SEV-ES guest AP, the hypervisor is not allowed to set the > RIP to the guest requested value. Instead, an SEV-ES AP must be transition > from 64-bit long mode to 16-bit real mode in response to an INIT-SIPI-SIPI > sequence. This requires a 16-bit code segment descriptor. > For PEI, create this descriptor in the reset vector GDT table. For DXE, create > this descriptor from the newly reserved entry at location 0x28. > > Cc: Eric Dong <eric.d...@intel.com> > Cc: Ray Ni <ray...@intel.com> > Cc: Laszlo Ersek <ler...@redhat.com> > Signed-off-by: Tom Lendacky <thomas.lenda...@amd.com> > --- > UefiCpuPkg/CpuDxe/CpuGdt.h | 4 ++-- > UefiCpuPkg/CpuDxe/CpuGdt.c | 8 ++++---- > UefiCpuPkg/ResetVector/Vtf0/Ia16/Real16ToFlat32.asm | 9 +++++++++ > 3 files changed, 15 insertions(+), 6 deletions(-) > > diff --git a/UefiCpuPkg/CpuDxe/CpuGdt.h b/UefiCpuPkg/CpuDxe/CpuGdt.h > index 3a0210b2f172..1c94487cbee8 100644 > --- a/UefiCpuPkg/CpuDxe/CpuGdt.h > +++ b/UefiCpuPkg/CpuDxe/CpuGdt.h > @@ -36,7 +36,7 @@ struct _GDT_ENTRIES { > GDT_ENTRY LinearCode; GDT_ENTRY SysData; GDT_ENTRY SysCode;- > GDT_ENTRY Spare4;+ GDT_ENTRY SysCode16; GDT_ENTRY LinearData64; > GDT_ENTRY LinearCode64; GDT_ENTRY Spare5;@@ -49,7 +49,7 @@ struct > _GDT_ENTRIES { > #define LINEAR_CODE_SEL OFFSET_OF (GDT_ENTRIES, LinearCode) > #define SYS_DATA_SEL OFFSET_OF (GDT_ENTRIES, SysData) #define > SYS_CODE_SEL OFFSET_OF (GDT_ENTRIES, SysCode)-#define SPARE4_SEL > OFFSET_OF (GDT_ENTRIES, Spare4)+#define SYS_CODE16_SEL OFFSET_OF > (GDT_ENTRIES, SysCode16) #define LINEAR_DATA64_SEL OFFSET_OF > (GDT_ENTRIES, LinearData64) #define LINEAR_CODE64_SEL OFFSET_OF > (GDT_ENTRIES, LinearCode64) #define SPARE5_SEL OFFSET_OF > (GDT_ENTRIES, Spare5)diff --git a/UefiCpuPkg/CpuDxe/CpuGdt.c > b/UefiCpuPkg/CpuDxe/CpuGdt.c > index 64efadeba601..a1ab543f2da5 100644 > --- a/UefiCpuPkg/CpuDxe/CpuGdt.c > +++ b/UefiCpuPkg/CpuDxe/CpuGdt.c > @@ -70,14 +70,14 @@ STATIC GDT_ENTRIES GdtTemplate = { > 0x0, }, //- // SPARE4_SEL+ // SYS_CODE16_SEL // {- 0x0, > // limit > 15:0+ 0x0FFFF, // limit 15:0 0x0, // base 15:0 > 0x0, // base > 23:16- 0x0, // type- 0x0, // limit 19:16, flags+ > 0x09A, // > present, ring 0, code, execute/read+ 0x08F, // page-granular, > 16-bit > 0x0, // base 31:24 }, //diff --git > a/UefiCpuPkg/ResetVector/Vtf0/Ia16/Real16ToFlat32.asm > b/UefiCpuPkg/ResetVector/Vtf0/Ia16/Real16ToFlat32.asm > index ce4ebfffb688..0e79a3984b16 100644 > --- a/UefiCpuPkg/ResetVector/Vtf0/Ia16/Real16ToFlat32.asm > +++ b/UefiCpuPkg/ResetVector/Vtf0/Ia16/Real16ToFlat32.asm > @@ -129,5 +129,14 @@ LINEAR_CODE64_SEL equ $-GDT_BASE > DB 0 ; base 31:24 %endif +; linear code segment > descriptor+LINEAR_CODE16_SEL equ $-GDT_BASE+ DW 0xffff ; > limit > 15:0+ DW 0 ; base 15:0+ DB 0 ; base > 23:16+ DB > PRESENT_FLAG(1)|DPL(0)|SYSTEM_FLAG(1)|DESC_TYPE(CODE32_TYPE)+ > DB > GRANULARITY_FLAG(1)|DEFAULT_SIZE32(0)|CODE64_FLAG(0)|UPPER_LIMI > T(0xf)+ DB 0 ; base 31:24+ GDT_END: -- > 2.27.0
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