diff --git a/OvmfPkg/ResetVector/Ia32/PageTables64.asm b/OvmfPkg/ResetVector/Ia32/PageTables64.asm index 6201cad1f5..db1590aedd 100644 --- a/OvmfPkg/ResetVector/Ia32/PageTables64.asm +++ b/OvmfPkg/ResetVector/Ia32/PageTables64.asm @@ -37,12 +37,66 @@ BITS 32 PAGE_READ_WRITE + \ PAGE_PRESENT) +; Check if Secure Encrypted Virtualization (SEV) feature is enabled +; +; If SEV is enabled then EAX will be at least 32 +; If SEV is disabled then EAX will be zero. +; +CheckSevFeature: + ; Check if we have a valid (0x8000_001F) CPUID leaf + mov eax, 0x80000000 + cpuid + + ; This check should fail on Intel or Non SEV AMD CPUs. In future if + ; Intel CPUs supports this CPUID leaf then we are guranteed to have exact + ; same bit definition. + cmp eax, 0x8000001f + jl NoSev + + ; Check for memory encryption feature: + ; CPUID Fn8000_001F[EAX] - Bit 1 + ; + mov eax, 0x8000001f + cpuid + bt eax, 1 + jnc NoSev + + ; Check if memory encryption is enabled + ; MSR_0xC0010131 - Bit 0 (SEV enabled) + mov ecx, 0xc0010131 + rdmsr + bt eax, 0 + jnc NoSev + + ; Get pte bit position to enable memory encryption + ; CPUID Fn8000_001F[EBX] - Bits 5:0 + ; + mov eax, ebx + and eax, 0x3f + jmp SevExit + +NoSev: + xor eax, eax + +SevExit: + OneTimeCallRet CheckSevFeature ; -; Modified: EAX, ECX +; Modified: EAX, EBX, ECX, EDX ; SetCr3ForPageTables64: + OneTimeCall CheckSevFeature + xor edx, edx + test eax, eax + jz SevNotActive + + ; If SEV is enabled, C-bit is always above 31 + sub eax, 32 + bts edx, eax + +SevNotActive: + ; ; For OVMF, build some initial page tables at ; PcdOvmfSecPageTablesBase - (PcdOvmfSecPageTablesBase + 0x6000). @@ -64,14 +118,19 @@ clearPageTablesMemoryLoop: ; Top level Page Directory Pointers (1 * 512GB entry) ; mov dword[PT_ADDR (0)], PT_ADDR (0x1000) + PAGE_PDP_ATTR + mov dword[PT_ADDR (4)], edx ; ; Next level Page Directory Pointers (4 * 1GB entries => 4GB) ; mov dword[PT_ADDR (0x1000)], PT_ADDR (0x2000) + PAGE_PDP_ATTR + mov dword[PT_ADDR (0x1004)], edx mov dword[PT_ADDR (0x1008)], PT_ADDR (0x3000) + PAGE_PDP_ATTR + mov dword[PT_ADDR (0x100C)], edx mov dword[PT_ADDR (0x1010)], PT_ADDR (0x4000) + PAGE_PDP_ATTR + mov dword[PT_ADDR (0x1014)], edx mov dword[PT_ADDR (0x1018)], PT_ADDR (0x5000) + PAGE_PDP_ATTR + mov dword[PT_ADDR (0x101C)], edx ; ; Page Table Entries (2048 * 2MB entries => 4GB) @@ -83,6 +142,7 @@ pageTableEntriesLoop: shl eax, 21 add eax, PAGE_2M_PDE_ATTR mov [ecx * 8 + PT_ADDR (0x2000 - 8)], eax + mov [(ecx * 8 + PT_ADDR (0x2000 - 8)) + 4], edx loop pageTableEntriesLoop ;