Re: [PATCH v10 45/46] UefiCpuPkg/MpInitLib: Prepare SEV-ES guest APs for OS use

["Dong, Eric" <eric.dong@intel.com>]

Reviewed-by: Eric Dong <eric.dong@intel.com>

> -----Original Message-----
> From: Tom Lendacky <thomas.lendacky@amd.com>
> Sent: Tuesday, July 14, 2020 10:38 PM
> To: devel@edk2.groups.io
> Cc: Brijesh Singh <brijesh.singh@amd.com>; Ard Biesheuvel
> <ard.biesheuvel@arm.com>; Dong, Eric <eric.dong@intel.com>; Justen,
> Jordan L <jordan.l.justen@intel.com>; Laszlo Ersek <lersek@redhat.com>;
> Gao, Liming <liming.gao@intel.com>; Kinney, Michael D
> <michael.d.kinney@intel.com>; Ni, Ray <ray.ni@intel.com>
> Subject: [PATCH v10 45/46] UefiCpuPkg/MpInitLib: Prepare SEV-ES guest APs
> for OS use
> 
> From: Tom Lendacky <thomas.lendacky@amd.com>
> 
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198
> 
> Before UEFI transfers control to the OS, it must park the AP. This is done
> using the AsmRelocateApLoop function to transition into 32-bit non-paging
> mode. For an SEV-ES guest, a few additional things must be
> done:
>   - AsmRelocateApLoop must be updated to support SEV-ES. This means
>     performing a VMGEXIT AP Reset Hold instead of an MWAIT or HLT loop.
>   - Since the AP must transition to real mode, a small routine is copied
>     to the WakeupBuffer area. Since the WakeupBuffer will be used by
>     the AP during OS booting, it must be placed in reserved memory.
>     Additionally, the AP stack must be located where it can be accessed
>     in real mode.
>   - Once the AP is in real mode it will transfer control to the
>     destination specified by the OS in the SEV-ES AP Jump Table. The
>     SEV-ES AP Jump Table address is saved by the hypervisor for the OS
>     using the GHCB VMGEXIT AP Jump Table exit code.
> 
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
>  UefiCpuPkg/Library/MpInitLib/MpLib.h          |   8 +-
>  UefiCpuPkg/Library/MpInitLib/DxeMpLib.c       |  54 +++++++-
>  UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm | 131
> ++++++++++++++++--
>  3 files changed, 175 insertions(+), 18 deletions(-)
> 
> diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.h
> b/UefiCpuPkg/Library/MpInitLib/MpLib.h
> index b1a9d99cb3eb..267aa5201c50 100644
> --- a/UefiCpuPkg/Library/MpInitLib/MpLib.h
> +++ b/UefiCpuPkg/Library/MpInitLib/MpLib.h
> @@ -293,7 +293,8 @@ struct _CPU_MP_DATA {
>    UINT64                         GhcbBase;
>  };
> 
> -#define AP_RESET_STACK_SIZE 64
> +#define AP_SAFE_STACK_SIZE  128
> +#define AP_RESET_STACK_SIZE AP_SAFE_STACK_SIZE
> 
>  #pragma pack(1)
> 
> @@ -349,8 +350,11 @@ VOID
>    IN BOOLEAN                 MwaitSupport,
>    IN UINTN                   ApTargetCState,
>    IN UINTN                   PmCodeSegment,
> +  IN UINTN                   Pm16CodeSegment,
>    IN UINTN                   TopOfApStack,
> -  IN UINTN                   NumberToFinish
> +  IN UINTN                   NumberToFinish,
> +  IN UINTN                   SevEsAPJumpTable,
> +  IN UINTN                   WakeupBuffer
>    );
> 
>  /**
> diff --git a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
> b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
> index 9115ff9e3e30..7165bcf3124a 100644
> --- a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
> +++ b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
> @@ -12,6 +12,7 @@
>  #include <Library/UefiBootServicesTableLib.h>
>  #include <Library/DebugAgentLib.h>
>  #include <Library/DxeServicesTableLib.h>
> +#include <Library/VmgExitLib.h>
>  #include <Register/Amd/Fam17Msr.h>
>  #include <Register/Amd/Ghcb.h>
> 
> @@ -85,6 +86,13 @@ GetWakeupBuffer (
>  {
>    EFI_STATUS              Status;
>    EFI_PHYSICAL_ADDRESS    StartAddress;
> +  EFI_MEMORY_TYPE         MemoryType;
> +
> +  if (PcdGetBool (PcdSevEsIsEnabled)) {
> +    MemoryType = EfiReservedMemoryType;  } else {
> +    MemoryType = EfiBootServicesData;
> +  }
> 
>    //
>    // Try to allocate buffer below 1M for waking vector.
> @@ -97,7 +105,7 @@ GetWakeupBuffer (
>    StartAddress = 0x88000;
>    Status = gBS->AllocatePages (
>                    AllocateMaxAddress,
> -                  EfiBootServicesData,
> +                  MemoryType,
>                    EFI_SIZE_TO_PAGES (WakeupBufferSize),
>                    &StartAddress
>                    );
> @@ -159,8 +167,10 @@ GetSevEsAPMemory (
>    VOID
>    )
>  {
> -  EFI_STATUS            Status;
> -  EFI_PHYSICAL_ADDRESS  StartAddress;
> +  EFI_STATUS                Status;
> +  EFI_PHYSICAL_ADDRESS      StartAddress;
> +  MSR_SEV_ES_GHCB_REGISTER  Msr;
> +  GHCB                      *Ghcb;
> 
>    //
>    // Allocate 1 page for AP jump table page @@ -176,6 +186,16 @@
> GetSevEsAPMemory (
> 
>    DEBUG ((DEBUG_INFO, "Dxe: SevEsAPMemory = %lx\n", (UINTN)
> StartAddress));
> 
> +  //
> +  // Save the SevEsAPMemory as the AP jump table.
> +  //
> +  Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);  Ghcb
> =
> + Msr.Ghcb;
> +
> +  VmgInit (Ghcb);
> +  VmgExit (Ghcb, SVM_EXIT_AP_JUMP_TABLE, 0, (UINT64) (UINTN)
> + StartAddress);  VmgDone (Ghcb);
> +
>    return (UINTN) StartAddress;
>  }
> 
> @@ -330,17 +350,26 @@ RelocateApLoop (
>    BOOLEAN                MwaitSupport;
>    ASM_RELOCATE_AP_LOOP   AsmRelocateApLoopFunc;
>    UINTN                  ProcessorNumber;
> +  UINTN                  StackStart;
> 
>    MpInitLibWhoAmI (&ProcessorNumber);
>    CpuMpData    = GetCpuMpData ();
>    MwaitSupport = IsMwaitSupport ();
> +  if (CpuMpData->SevEsIsEnabled) {
> +    StackStart = CpuMpData->SevEsAPResetStackStart;
> +  } else {
> +    StackStart = mReservedTopOfApStack;  }
>    AsmRelocateApLoopFunc = (ASM_RELOCATE_AP_LOOP) (UINTN)
> mReservedApLoopFunc;
>    AsmRelocateApLoopFunc (
>      MwaitSupport,
>      CpuMpData->ApTargetCState,
>      CpuMpData->PmCodeSegment,
> -    mReservedTopOfApStack - ProcessorNumber * AP_SAFE_STACK_SIZE,
> -    (UINTN) &mNumberToFinish
> +    CpuMpData->Pm16CodeSegment,
> +    StackStart - ProcessorNumber * AP_SAFE_STACK_SIZE,
> +    (UINTN) &mNumberToFinish,
> +    CpuMpData->SevEsAPBuffer,
> +    CpuMpData->WakeupBuffer
>      );
>    //
>    // It should never reach here
> @@ -374,6 +403,21 @@ MpInitChangeApLoopCallback (
>    while (mNumberToFinish > 0) {
>      CpuPause ();
>    }
> +
> +  if (CpuMpData->SevEsIsEnabled && (CpuMpData->WakeupBuffer !=
> (UINTN) -1)) {
> +    //
> +    // There are APs present. Re-use reserved memory area below 1MB from
> +    // WakeupBuffer as the area to be used for transitioning to 16-bit mode
> +    // in support of booting of the AP by an OS.
> +    //
> +    CopyMem (
> +      (VOID *) CpuMpData->WakeupBuffer,
> +      (VOID *) (CpuMpData->AddressMap.RendezvousFunnelAddress +
> +                  CpuMpData->AddressMap.SwitchToRealPM16ModeOffset),
> +      CpuMpData->AddressMap.SwitchToRealPM16ModeSize
> +      );
> +  }
> +
>    DEBUG ((DEBUG_INFO, "%a() done!\n", __FUNCTION__));  }
> 
> diff --git a/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
> b/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
> index 6956b408d004..3b8ec477b8b3 100644
> --- a/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
> +++ b/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
> @@ -465,6 +465,10 @@ BITS 16
>      ;     - IP for Real Mode (two bytes)
>      ;     - CS for Real Mode (two bytes)
>      ;
> +    ; This label is also used with AsmRelocateApLoop. During MP finalization,
> +    ; the code from PM16Mode to SwitchToRealProcEnd is copied to the start
> of
> +    ; the WakeupBuffer, allowing a parked AP to be booted by an OS.
> +    ;
>  PM16Mode:
>      mov        eax, cr0                    ; Read CR0
>      btr        eax, 0                      ; Set PE=0
> @@ -487,32 +491,95 @@ PM16Mode:
>  SwitchToRealProcEnd:
> 
>  ;-------------------------------------------------------------------------------------
> -;  AsmRelocateApLoop (MwaitSupport, ApTargetCState, PmCodeSegment,
> TopOfApStack, CountTofinish);
> +;  AsmRelocateApLoop (MwaitSupport, ApTargetCState, PmCodeSegment,
> +Pm16CodeSegment, TopOfApStack, CountTofinish, SevEsAPJumpTable,
> +WakeupBuffer);
>  ;-------------------------------------------------------------------------------------
>  global ASM_PFX(AsmRelocateApLoop)
>  ASM_PFX(AsmRelocateApLoop):
>  AsmRelocateApLoopStart:
>  BITS 64
> +    cmp        qword [rsp + 56], 0
> +    je         NoSevEs
> +
> +    ;
> +    ; Perform some SEV-ES related setup before leaving 64-bit mode
> +    ;
> +    push       rcx
> +    push       rdx
> +
> +    ;
> +    ; Get the RDX reset value using CPUID
> +    ;
> +    mov        rax, 1
> +    cpuid
> +    mov        rsi, rax          ; Save off the reset value for RDX
> +
> +    ;
> +    ; Prepare the GHCB for the AP_HLT_LOOP VMGEXIT call
> +    ;   - Must be done while in 64-bit long mode so that writes to
> +    ;     the GHCB memory will be unencrypted.
> +    ;   - No NAE events can be generated once this is set otherwise
> +    ;     the AP_RESET_HOLD SW_EXITCODE will be overwritten.
> +    ;
> +    mov        rcx, 0xc0010130
> +    rdmsr                        ; Retrieve current GHCB address
> +    shl        rdx, 32
> +    or         rdx, rax
> +
> +    mov        rdi, rdx
> +    xor        rax, rax
> +    mov        rcx, 0x800
> +    shr        rcx, 3
> +    rep stosq                    ; Clear the GHCB
> +
> +    mov        rax, 0x80000004   ; VMGEXIT AP_RESET_HOLD
> +    mov        [rdx + 0x390], rax
> +
> +    pop        rdx
> +    pop        rcx
> +
> +NoSevEs:
>      cli                          ; Disable interrupt before switching to 32-bit mode
> -    mov        rax, [rsp + 40]   ; CountTofinish
> +    mov        rax, [rsp + 48]   ; CountTofinish
>      lock dec   dword [rax]       ; (*CountTofinish)--
> -    mov        rsp, r9
> -    push       rcx
> -    push       rdx
> 
> -    lea        rsi, [PmEntry]    ; rsi <- The start address of transition code
> +    mov        rax, [rsp + 56]   ; SevEsAPJumpTable
> +    mov        rbx, [rsp + 64]   ; WakeupBuffer
> +    mov        rsp, [rsp + 40]   ; TopOfApStack
> +
> +    push       rax               ; Save SevEsAPJumpTable
> +    push       rbx               ; Save WakeupBuffer
> +    push       r9                ; Save Pm16CodeSegment
> +    push       rcx               ; Save MwaitSupport
> +    push       rdx               ; Save ApTargetCState
> +
> +    lea        rax, [PmEntry]    ; rax <- The start address of transition code
> 
>      push       r8
> -    push       rsi
> -    DB         0x48
> -    retf
> +    push       rax
> +
> +    ;
> +    ; Clear R8 - R15, for reset, before going into 32-bit mode
> +    ;
> +    xor        r8, r8
> +    xor        r9, r9
> +    xor        r10, r10
> +    xor        r11, r11
> +    xor        r12, r12
> +    xor        r13, r13
> +    xor        r14, r14
> +    xor        r15, r15
> +
> +    ;
> +    ; Far return into 32-bit mode
> +    ;
> +o64 retf
> +
>  BITS 32
>  PmEntry:
>      mov        eax, cr0
>      btr        eax, 31           ; Clear CR0.PG
>      mov        cr0, eax          ; Disable paging and caches
> 
> -    mov        ebx, edx          ; Save EntryPoint to rbx, for rdmsr will overwrite rdx
>      mov        ecx, 0xc0000080
>      rdmsr
>      and        ah, ~ 1           ; Clear LME
> @@ -525,6 +592,8 @@ PmEntry:
>      add        esp, 4
>      pop        ecx,
>      add        esp, 4
> +
> +MwaitCheck:
>      cmp        cl, 1              ; Check mwait-monitor support
>      jnz        HltLoop
>      mov        ebx, edx           ; Save C-State to ebx
> @@ -538,10 +607,50 @@ MwaitLoop:
>      shl        eax, 4
>      mwait
>      jmp        MwaitLoop
> +
>  HltLoop:
> +    pop        edx                ; PM16CodeSegment
> +    add        esp, 4
> +    pop        ebx                ; WakeupBuffer
> +    add        esp, 4
> +    pop        eax                ; SevEsAPJumpTable
> +    add        esp, 4
> +    cmp        eax, 0             ; Check for SEV-ES
> +    je         DoHlt
> +
> +    cli
> +    ;
> +    ; SEV-ES is enabled, use VMGEXIT (GHCB information already
> +    ; set by caller)
> +    ;
> +BITS 64
> +    rep        vmmcall
> +BITS 32
> +
> +    ;
> +    ; Back from VMGEXIT AP_HLT_LOOP
> +    ;   Push the FLAGS/CS/IP values to use
> +    ;
> +    push       word 0x0002        ; EFLAGS
> +    xor        ecx, ecx
> +    mov        cx, [eax + 2]      ; CS
> +    push       cx
> +    mov        cx, [eax]          ; IP
> +    push       cx
> +    push       word 0x0000        ; For alignment, will be discarded
> +
> +    push       edx
> +    push       ebx
> +
> +    mov        edx, esi           ; Restore RDX reset value
> +
> +    retf
> +
> +DoHlt:
>      cli
>      hlt
> -    jmp        HltLoop
> +    jmp        DoHlt
> +
>  BITS 64
>  AsmRelocateApLoopEnd:
> 
> --
> 2.27.0