OvmfPkg/TdxDxe/X64/ApRunLoop.nasm

;------------------------------------------------------------------------------ ;
; Copyright (c) 2021, Intel Corporation. All rights reserved.<BR>
; SPDX-License-Identifier: BSD-2-Clause-Patent
;
; Module Name:
;
;   ApRunLoop.nasm
;
; Abstract:
;
;   This is the assembly code for run loop for APs in the guest TD
;
;-------------------------------------------------------------------------------

%include "TdxCommondefs.inc"

DEFAULT REL

SECTION .text

BITS 64

%define TDVMCALL_EXPOSE_REGS_MASK       0xffcc
%define TDVMCALL                        0x0
%define EXIT_REASON_CPUID               0xa

%macro  tdcall  0
  db  0x66, 0x0f, 0x01, 0xcc
%endmacro

%macro tdcall_regs_preamble 2
    mov rax, %1

    xor rcx, rcx
    mov ecx, %2

    ; R10 = 0 (standard TDVMCALL)

    xor r10d, r10d

    ; Zero out unused (for standard TDVMCALL) registers to avoid leaking
    ; secrets to the VMM.

    xor esi, esi
    xor edi, edi

    xor edx, edx
    xor ebp, ebp
    xor r8d, r8d
    xor r9d, r9d
    xor r14, r14
    xor r15, r15
%endmacro

;
; Relocated Ap Mailbox loop
;
; @param[in]  RBX:  Relocated mailbox address
; @param[in]  RBP:  vCpuId
;
; @return     None  This routine does not return
;
global ASM_PFX(AsmRelocateApMailBoxLoop)
ASM_PFX(AsmRelocateApMailBoxLoop):
AsmRelocateApMailBoxLoopStart:

    mov         r11, EXIT_REASON_CPUID
    mov         r12, 0xb
    tdcall_regs_preamble TDVMCALL, TDVMCALL_EXPOSE_REGS_MASK
    tdcall
    test        r10, r10
    jnz         Panic
    mov         r8, r15

MailBoxLoop:
    ; Spin until command set
    cmp        dword [rbx + CommandOffset], MpProtectedModeWakeupCommandNoop
    je         MailBoxLoop
    ; Determine if this is a broadcast or directly for my apic-id, if not, ignore
    cmp        dword [rbx + ApicidOffset], MailboxApicidBroadcast
    je         MailBoxProcessCommand
    cmp        dword [rbx + ApicidOffset], r8d
    jne        MailBoxLoop
MailBoxProcessCommand:
    cmp        dword [rbx + CommandOffset], MpProtectedModeWakeupCommandWakeup
    je         MailBoxWakeUp
    cmp        dword [rbx + CommandOffset], MpProtectedModeWakeupCommandSleep
    je         MailBoxSleep
    ; Don't support this command, so ignore
    jmp        MailBoxLoop
MailBoxWakeUp:
    mov        rax, [rbx + WakeupVectorOffset]
    ; OS sends a wakeup command for a given APIC ID, firmware is supposed to reset
    ; the command field back to zero as acknowledgement.
    mov        qword [rbx + CommandOffset], 0
    jmp        rax
MailBoxSleep:
    jmp       $
Panic:
    ud2
BITS 64
AsmRelocateApMailBoxLoopEnd:

;-------------------------------------------------------------------------------------
;  AsmGetRelocationMap (&RelocationMap);
;-------------------------------------------------------------------------------------
global ASM_PFX(AsmGetRelocationMap)
ASM_PFX(AsmGetRelocationMap):
    lea        rax, [AsmRelocateApMailBoxLoopStart]
    mov        qword [rcx], rax
    mov        qword [rcx +  8h], AsmRelocateApMailBoxLoopEnd - AsmRelocateApMailBoxLoopStart
    ret