[PATCH V3 15/29] OvmfPkg: Update SecEntry.nasm to support Tdx

["Min Xu" <min.m.xu@intel.com>]

RFC: https://bugzilla.tianocore.org/show_bug.cgi?id=3429

In TDX BSP and APs goes to the same entry point in SecEntry.nasm.

BSP initialize the temporary stack and then jumps to SecMain, just as
legacy Ovmf does.

APs spin in a modified mailbox loop using initial mailbox structure.
Its structure defition is in OvmfPkg/Include/IndustryStandard/IntelTdx.h.
APs wait for command to see if the command is for me. If so execute the
command.

There are 2 commands are supported:
 - WakeUp:
   BSP issues this command to move APs to final OS spinloop and Mailbox
   in reserved memory.
 - AcceptPages:
   To mitigate the performance impact of accepting pages in SEC phase on
   BSP, BSP will parse memory resources and assign each AP the task of
   accepting a subset of pages. This command may be called several times
   until all memory resources are processed. In accepting pages, PageLevel
   may fall back to smaller one if SIZE_MISMATCH error is returned.

TdxCommondefs.inc is added which includes the common definitions used by
the APs in SecEntry.nasm.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>
---
 OvmfPkg/Include/TdxCommondefs.inc |  51 +++++
 OvmfPkg/Sec/SecMain.inf           |   1 +
 OvmfPkg/Sec/X64/SecEntry.nasm     | 314 ++++++++++++++++++++++++++++++
 3 files changed, 366 insertions(+)
 create mode 100644 OvmfPkg/Include/TdxCommondefs.inc

diff --git a/OvmfPkg/Include/TdxCommondefs.inc b/OvmfPkg/Include/TdxCommondefs.inc
new file mode 100644
index 000000000000..970eac96592a
--- /dev/null
+++ b/OvmfPkg/Include/TdxCommondefs.inc
@@ -0,0 +1,51 @@
+;------------------------------------------------------------------------------
+; @file
+; TDX Common defitions used by the APs in mailbox
+;
+; Copyright (c) 2021, Intel Corporation. All rights reserved.<BR>
+; SPDX-License-Identifier: BSD-2-Clause-Patent
+;
+;------------------------------------------------------------------------------
+
+CommandOffset                             equ       00h
+ApicidOffset                              equ       04h
+WakeupVectorOffset                        equ       08h
+OSArgsOffset                              equ       10h
+FirmwareArgsOffset                        equ       800h
+WakeupArgsRelocatedMailBox                equ       800h
+AcceptPageArgsPhysicalStart               equ       800h
+AcceptPageArgsPhysicalEnd                 equ       808h
+AcceptPageArgsChunkSize                   equ       810h
+AcceptPageArgsPageSize                    equ       818h
+CpuArrivalOffset                          equ       900h
+CpusExitingOffset                         equ       0a00h
+TalliesOffset                             equ       0a08h
+ErrorsOffset                              equ       0e08h
+
+SIZE_4KB                                  equ       1000h
+SIZE_2MB                                  equ       200000h
+SIZE_1GB                                  equ       40000000h
+
+PAGE_ACCEPT_LEVEL_4K                      equ       0
+PAGE_ACCEPT_LEVEL_2M                      equ       1
+PAGE_ACCEPT_LEVEL_1G                      equ       2
+
+TDX_PAGE_ALREADY_ACCEPTED                 equ       0x00000b0a
+TDX_PAGE_SIZE_MISMATCH                    equ       0xc0000b0b
+
+; Errors of APs in Mailbox
+ERROR_NON                                 equ       0
+ERROR_INVALID_ACCEPT_PAGE_SIZE            equ       1
+ERROR_ACCEPT_PAGE_ERROR                   equ       2
+ERROR_INVALID_FALLBACK_PAGE_LEVEL         equ       3
+
+MpProtectedModeWakeupCommandNoop          equ       0
+MpProtectedModeWakeupCommandWakeup        equ       1
+MpProtectedModeWakeupCommandSleep         equ       2
+MpProtectedModeWakeupCommandAcceptPages   equ       3
+
+MailboxApicIdInvalid                      equ       0xffffffff
+MailboxApicidBroadcast                    equ       0xfffffffe
+
+%define TDCALL_TDINFO                          0x1
+%define TDCALL_TDACCEPTPAGE                    0x6
diff --git a/OvmfPkg/Sec/SecMain.inf b/OvmfPkg/Sec/SecMain.inf
index ea4b9611f52d..6083fa21a433 100644
--- a/OvmfPkg/Sec/SecMain.inf
+++ b/OvmfPkg/Sec/SecMain.inf
@@ -72,6 +72,7 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdInitValueInTempStack
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfConfidentialComputingWorkAreaHeader
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaBase
+  gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecGhcbBackupBase
 
 [FeaturePcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdSmmSmramRequire
diff --git a/OvmfPkg/Sec/X64/SecEntry.nasm b/OvmfPkg/Sec/X64/SecEntry.nasm
index 1cc680a70716..d0833db68410 100644
--- a/OvmfPkg/Sec/X64/SecEntry.nasm
+++ b/OvmfPkg/Sec/X64/SecEntry.nasm
@@ -10,12 +10,17 @@
 ;------------------------------------------------------------------------------
 
 #include <Base.h>
+%include "TdxCommondefs.inc"
 
 DEFAULT REL
 SECTION .text
 
 extern ASM_PFX(SecCoreStartupWithStack)
 
+%macro  tdcall  0
+  db  0x66, 0x0f, 0x01, 0xcc
+%endmacro
+
 ;
 ; SecCore Entry Point
 ;
@@ -35,6 +40,32 @@ extern ASM_PFX(SecCoreStartupWithStack)
 global ASM_PFX(_ModuleEntryPoint)
 ASM_PFX(_ModuleEntryPoint):
 
+    ;
+    ; Guest type is stored in OVMF_WORK_AREA
+    ;
+    %define OVMF_WORK_AREA        FixedPcdGet32 (PcdOvmfWorkAreaBase)
+    %define VM_GUEST_TYPE_TDX     2
+    mov     eax, OVMF_WORK_AREA
+    cmp     byte[eax], VM_GUEST_TYPE_TDX
+    jne     InitStack
+
+    mov     rax, TDCALL_TDINFO
+    tdcall
+
+    ;
+    ; R8  [31:0]  NUM_VCPUS
+    ;     [63:32] MAX_VCPUS
+    ; R9  [31:0]  VCPU_INDEX
+    ; Td Guest set the VCPU0 as the BSP, others are the APs
+    ; APs jump to spinloop and get released by DXE's MpInitLib
+    ;
+    mov     rax, r9
+    and     rax, 0xffff
+    test    rax, rax
+    jne     ParkAp
+
+InitStack:
+
     ;
     ; Fill the temporary RAM with the initial stack value.
     ; The loop below will seed the heap as well, but that's harmless.
@@ -67,3 +98,286 @@ ASM_PFX(_ModuleEntryPoint):
     sub     rsp, 0x20
     call    ASM_PFX(SecCoreStartupWithStack)
 
+    ;
+    ; Note: BSP never gets here. APs will be unblocked by DXE
+    ;
+    ; R8  [31:0]  NUM_VCPUS
+    ;     [63:32] MAX_VCPUS
+    ; R9  [31:0]  VCPU_INDEX
+    ;
+ParkAp:
+
+    mov     rbp,  r9
+
+.do_wait_loop:
+    mov     rsp, FixedPcdGet32 (PcdOvmfSecGhcbBackupBase)
+
+    ;
+    ; register itself in [rsp + CpuArrivalOffset]
+    ;
+    mov       rax, 1
+    lock xadd dword [rsp + CpuArrivalOffset], eax
+    inc       eax
+
+.check_arrival_cnt:
+    cmp       eax, r8d
+    je        .check_command
+    mov       eax, dword[rsp + CpuArrivalOffset]
+    jmp       .check_arrival_cnt
+
+.check_command:
+    mov     eax, dword[rsp + CommandOffset]
+    cmp     eax, MpProtectedModeWakeupCommandNoop
+    je      .check_command
+
+    cmp     eax, MpProtectedModeWakeupCommandWakeup
+    je      .do_wakeup
+
+    cmp     eax, MpProtectedModeWakeupCommandAcceptPages
+    jne     .check_command
+
+    ;
+    ; AP Accept Pages
+    ;
+    ; Accept Pages in TDX is time-consuming, especially for big memory.
+    ; One of the mitigation is to accept pages by BSP and APs parallely.
+    ;
+    ; For example, there are 4 CPUs (1 BSP and 3 APs). Totally there are
+    ; 1G memory to be accepted.
+    ;
+    ; BSP is responsible for the memory regions of:
+    ;    Start : StartAddress + ChunkSize * (4) * Index
+    ;    Length: ChunkSize
+    ; APs is reponsible for the memory regions of:
+    ;    Start : StartAddress + ChunkSize * (4) * Index + ChunkSize * CpuId
+    ;    Length: ChunkSize
+    ;
+    ; TDCALL_TDACCEPTPAGE supports the PageSize of 4K and 2M. Sometimes when
+    ; the PageSize is 2M, TDX_PAGE_SIZE_MISMATCH is returned as the error code.
+    ; In this case, TDVF need fall back to 4k PageSize to accept again.
+    ;
+    ; If any errors happened in accept pages, an error code is recorded in
+    ; Mailbox [ErrorsOffset + CpuIndex]
+    ;
+.ap_accept_page:
+
+    ;
+    ; Clear the errors and fallback flag
+    ;
+    mov     al, ERROR_NON
+    mov     byte[rsp + ErrorsOffset + rbp], al
+    xor     r12, r12
+
+    ;
+    ; Get PhysicalAddress/ChunkSize/PageSize
+    ;
+    mov     rcx, [rsp + AcceptPageArgsPhysicalStart]
+    mov     rbx, [rsp + AcceptPageArgsChunkSize]
+
+    ;
+    ; Set AcceptPageLevel based on the AcceptPagesize
+    ; Currently only 2M/4K page size is acceptable
+    ;
+    mov     r15, [rsp + AcceptPageArgsPageSize]
+    cmp     r15, SIZE_4KB
+    je      .set_4kb
+    cmp     r15, SIZE_2MB
+    je      .set_2mb
+
+    mov     al, ERROR_INVALID_ACCEPT_PAGE_SIZE
+    mov     byte[rsp + ErrorsOffset + rbp], al
+    jmp     .do_finish_command
+
+.set_4kb:
+    mov     r15, PAGE_ACCEPT_LEVEL_4K
+    jmp     .physical_address
+
+.set_2mb:
+    mov     r15, PAGE_ACCEPT_LEVEL_2M
+
+.physical_address:
+    ;
+    ; PhysicalAddress += (CpuId * ChunkSize)
+    ;
+    xor     rdx, rdx
+    mov     eax, ebp
+    mul     ebx
+    add     rcx, rax
+    shl     rdx, 32
+    add     rcx, rdx
+
+.do_accept_next_range:
+    ;
+    ; Make sure we don't accept page beyond ending page
+    ; This could happen is ChunkSize crosses the end of region
+    ;
+    cmp     rcx, [rsp + AcceptPageArgsPhysicalEnd ]
+    jge     .do_finish_command
+
+    ;
+    ; Save starting address for this region
+    ;
+    mov     r11, rcx
+
+    ;
+    ; Size = MIN(ChunkSize, PhysicalEnd - PhysicalAddress);
+    ;
+    mov     rax, [rsp + AcceptPageArgsPhysicalEnd]
+    sub     rax, rcx
+    cmp     rax, rbx
+    jge     .do_accept_loop
+    mov     rbx, rax
+
+.do_accept_loop:
+    ;
+    ; RCX: Accept address
+    ; R15: Accept Page Level
+    ; R12: Flag of fall back accept
+    ;
+    mov     rax, TDCALL_TDACCEPTPAGE
+    xor     rdx, rdx
+    or      rcx, r15
+
+    tdcall
+
+    ;
+    ; Check status code in RAX
+    ;
+    test    rax, rax
+    jz      .accept_success
+
+    shr     rax, 32
+    cmp     eax, TDX_PAGE_ALREADY_ACCEPTED
+    jz      .already_accepted
+
+    cmp     eax, TDX_PAGE_SIZE_MISMATCH
+    jz      .accept_size_mismatch
+
+    ;
+    ; other error
+    ;
+    mov     al, ERROR_ACCEPT_PAGE_ERROR
+    mov     byte[rsp + ErrorsOffset + rbp], al
+    jmp     .do_finish_command
+
+.accept_size_mismatch:
+    ;
+    ; Check the current PageLevel.
+    ; ACCEPT_LEVEL_4K is the least level and cannot fall back any more.
+    ; If in this case, just record the error and return
+    ;
+    cmp     r15, PAGE_ACCEPT_LEVEL_4K
+    jne     .do_fallback_accept
+    mov     al, ERROR_INVALID_FALLBACK_PAGE_LEVEL
+    mov     byte[rsp + ErrorsOffset + rbp], al
+    jmp     .do_finish_command
+
+.do_fallback_accept:
+    ;
+    ; In fall back accept, just loop 512 times (2M = 512 * 4K)
+    ; Save the rcx in r13.
+    ; Decrease the PageLevel in R15.
+    ; R12 indicates it is in a fall back accept loop.
+    ;
+    mov     r14, 512
+    and     rcx, ~0x3ULL
+    mov     r13, rcx
+    xor     rdx, rdx
+    dec     r15
+    mov     r12, 1
+
+    jmp     .do_accept_loop
+
+.accept_success:
+    ;
+    ; Keep track of how many accepts per cpu
+    ;
+    inc dword[rsp + TalliesOffset + rbp * 4]
+
+    ;
+    ; R12 indicate whether it is a fall back accept
+    ; If it is a success of fall back accept
+    ; Just loop 512 times to .do_accept_loop
+    ;
+    test    r12, r12
+    jz      .normal_accept_success
+
+    ;
+    ; This is fallback accept success
+    ;
+    add     rcx, SIZE_4KB
+    dec     r14
+    test    r14, r14
+    jz      .fallback_accept_done
+    jmp     .do_accept_loop
+
+.fallback_accept_done:
+    ;
+    ; Fall back accept done.
+    ; Restore the start address to RCX from R13
+    ; Clear the fall back accept flag
+    ;
+    mov     rcx, r13
+    inc     r15
+    xor     r12, r12
+
+.already_accepted:
+    ;
+    ; Handle the sitution of fall back accpet
+    ;
+    test    r12, r12
+    jnz     .accept_success
+
+.normal_accept_success:
+    ;
+    ; Reduce accept size by a PageSize, and increment address
+    ;
+    mov     r12, [rsp + AcceptPageArgsPageSize]
+    sub     rbx, r12
+    add     rcx, r12
+    xor     r12, r12
+
+    ;
+    ; We may be given multiple pages to accept, make sure we
+    ; aren't done
+    ;
+    test    rbx, rbx
+    jne     .do_accept_loop
+
+    ;
+    ; Restore address before, and then increment by stride (num-cpus * ChunkSize)
+    ;
+    xor     rdx, rdx
+    mov     rcx, r11
+    mov     eax, r8d
+    mov     ebx, [rsp + AcceptPageArgsChunkSize]
+    mul     ebx
+    add     rcx, rax
+    shl     rdx, 32
+    add     rcx, rdx
+    jmp     .do_accept_next_range
+
+.do_finish_command:
+    mov       eax, 0FFFFFFFFh
+    lock xadd dword [rsp + CpusExitingOffset], eax
+    dec       eax
+
+.check_exiting_cnt:
+    cmp       eax, 0
+    je        .do_wait_loop
+    mov       eax, dword[rsp + CpusExitingOffset]
+    jmp       .check_exiting_cnt
+
+.do_wakeup:
+    ;
+    ; BSP sets these variables before unblocking APs
+    ;   RAX:  WakeupVectorOffset
+    ;   RBX:  Relocated mailbox address
+    ;   RBP:  vCpuId
+    ;
+    mov     rax, 0
+    mov     eax, dword[rsp + WakeupVectorOffset]
+    mov     rbx, [rsp + WakeupArgsRelocatedMailBox]
+    nop
+    jmp     rax
+    jmp     $
-- 
2.29.2.windows.2