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.dong@intel.com> Cc: Ray Ni <ray.ni@intel.com> Cc: Laszlo Ersek <lersek@redhat.com> Reviewed-by: Eric Dong <eric.dong@intel.com> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> Regression-tested-by: Laszlo Ersek <lersek@redhat.com>
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@@ -70,14 +70,14 @@ STATIC GDT_ENTRIES GdtTemplate = {
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0x0,
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},
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//
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// SPARE4_SEL
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// SYS_CODE16_SEL
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//
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{
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0x0, // limit 15:0
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0x0FFFF, // limit 15:0
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0x0, // base 15:0
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0x0, // base 23:16
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0x0, // type
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0x0, // limit 19:16, flags
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0x09A, // present, ring 0, code, execute/read
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0x08F, // page-granular, 16-bit
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0x0, // base 31:24
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},
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//
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