It's not a requirement. > -----Original Message----- > From: Tom Lendacky <thomas.lenda...@amd.com> > Sent: Friday, December 13, 2019 5:19 AM > To: devel@edk2.groups.io; Ni, Ray <ray...@intel.com> > Cc: Justen, Jordan L <jordan.l.jus...@intel.com>; Laszlo Ersek > <ler...@redhat.com>; Ard Biesheuvel > <ard.biesheu...@linaro.org>; Kinney, Michael D <michael.d.kin...@intel.com>; > Gao, Liming <liming....@intel.com>; Dong, > Eric <eric.d...@intel.com>; Brijesh Singh <brijesh.si...@amd.com>; Wang, Jian > J <jian.j.w...@intel.com>; Wu, Hao A > <hao.a...@intel.com>; Bi, Dandan <dandan...@intel.com> > Subject: Re: [edk2-devel] [RFC PATCH v3 33/43] MdeModulePkg: Reserve a 16-bit > protected mode code segment descriptor > > On 12/12/19 12:57 AM, Ni, Ray via Groups.Io wrote: > > Is the 16bit code segment descriptor needed in early DXE before CpuDxe (DXE > > MP)? > > I don't believe it is. I did this to keep all of the CS descriptors > consistent since the ones here seemed to line up with the ones in > UefiCpuPkg/CpuDxe/CpuGdt.c. I can remove this change if that isn't > a requirement. > > Thanks, > Tom > > > > >> -----Original Message----- > >> From: Tom Lendacky <thomas.lenda...@amd.com> > >> Sent: Thursday, November 21, 2019 4:07 AM > >> To: devel@edk2.groups.io > >> Cc: Justen, Jordan L <jordan.l.jus...@intel.com>; Laszlo Ersek > >> <ler...@redhat.com>; Ard Biesheuvel > >> <ard.biesheu...@linaro.org>; Kinney, Michael D > >> <michael.d.kin...@intel.com>; Gao, Liming <liming....@intel.com>; > Dong, > >> Eric <eric.d...@intel.com>; Ni, Ray <ray...@intel.com>; Brijesh Singh > >> <brijesh.si...@amd.com>; Wang, Jian J > >> <jian.j.w...@intel.com>; Wu, Hao A <hao.a...@intel.com>; Bi, Dandan > >> <dandan...@intel.com> > >> Subject: [RFC PATCH v3 33/43] MdeModulePkg: Reserve a 16-bit protected > >> mode code segment descriptor > >> > >> BZ: > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.tianocore.org%2Fshow_bug.cgi%3Fid%3D21 > 98&data=02%7C01%7Cthomas.lendacky%40amd.com%7C8ec88e8912cd4b99eb0f08d77ed09b2c%7C3dd8961fe4884e60 > 8e11a82d994e183d%7C0%7C0%7C637117306738013792&sdata=PwSQc53mtPMUTALaRhQrcQzGI3ooPUMhcktYLi1ezfk > %3D&reserved=0 > >> > >> SEV-ES guest AP boot support needs to transition from 64-bit long mode > >> into 16-bit real mode. This will require a 16-bit code segment descriptor. > >> Reserve one of the spare segment descriptors (0x28) for this purpose. > >> > >> Cc: Jian J Wang <jian.j.w...@intel.com> > >> Cc: Hao A Wu <hao.a...@intel.com> > >> Cc: Dandan Bi <dandan...@intel.com> > >> Cc: Liming Gao <liming....@intel.com> > >> Signed-off-by: Tom Lendacky <thomas.lenda...@amd.com> > >> --- > >> MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c > b/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c > >> index 284b34818ca7..c9cf2e36214f 100644 > >> --- a/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c > >> +++ b/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c > >> @@ -33,7 +33,7 @@ GLOBAL_REMOVE_IF_UNREFERENCED IA32_GDT gGdtEntries[] = { > >> /* 0x10 */ {{0xffff, 0, 0, 0xf, 1, 0, 1, 0xf, 0, 0, 1, 1, 0}}, > >> //linear code segment descriptor > >> /* 0x18 */ {{0xffff, 0, 0, 0x3, 1, 0, 1, 0xf, 0, 0, 1, 1, 0}}, > >> //system data segment descriptor > >> /* 0x20 */ {{0xffff, 0, 0, 0xa, 1, 0, 1, 0xf, 0, 0, 1, 1, 0}}, > >> //system code segment descriptor > >> -/* 0x28 */ {{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}}, > >> //spare segment descriptor > >> +/* 0x28 */ {{0xffff, 0, 0, 0xa, 1, 0, 1, 0xf, 0, 0, 0, 1, 0}}, > >> //system code16 segment descriptor > >> /* 0x30 */ {{0xffff, 0, 0, 0x2, 1, 0, 1, 0xf, 0, 0, 1, 1, 0}}, > >> //system data segment descriptor > >> /* 0x38 */ {{0xffff, 0, 0, 0xa, 1, 0, 1, 0xf, 0, 1, 0, 1, 0}}, > >> //system code segment descriptor > >> /* 0x40 */ {{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}}, > >> //spare segment descriptor > >> -- > >> 2.17.1 > > > > > > > >
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