Re: [RFC PATCH v2 09/10] OvmfPkg/QemuFwCfgLib: Add Secure Encrypted Virtualization (SEV) support

[Laszlo Ersek <lersek@redhat.com>]

On 03/27/17 21:24, Brijesh Singh wrote:
> On Mon, Mar 27, 2017 at 5:19 AM, Laszlo Ersek <lersek@redhat.com> wrote:

>> - regarding InternalQemuFwCfgDmaBytes(): would it be possible to hook
>> the SEV-related tricks into the existent function, rather than
>> copy+modify the entire function as InternalQemuFwCfgSevDmaBytes()? It
>> seems to me that a conditional "prologue" and "epilogue" in
>> InternalQemuFwCfgDmaBytes() could do the trick.
>>
>>
> I wanted to reuse the existing function but I was not sure how do you
> wanted me to handle static allocation of "Access" variable inside
> the InternalQemuFwCfgDmaBytes()
> 
>  VOID
>  InternalQemuFwCfgDmaBytes (
>    IN     UINT32   Size,
>    IN OUT VOID     *Buffer OPTIONAL,
>    IN     UINT32   Control
>    )
>  {
>    volatile FW_CFG_DMA_ACCESS Access;
>    UINT32                     AccessHigh, AccessLow;
>    UINT32                     Status;
> 
> 
> The "Access" variable is statically allocated inside this function,

The storage duration of "Access" is not "static", it is "automatic".
(Put more colloquially, it is on the stack, it is not a global variable.)

But, I do understand the point; for the SEV case, you need it to be
dynamically allocated *and* exposed to the hypervisor, with
InternalQemuFwCfgSevDmaAllocateBuffer().

So here's my suggestion: in the following (suggested) list of patches:

- new interfaces in QemuFwCfgLibInternal.h
- implementation of new APIs for SEC instance
- implementation of new APIs for PEI instance
- implementation of new APIs for DXE instance
- call new APIs from common code

the last part should actually be two patches (so not 5 but 6 patches in
total).

First, please modify InternalQemuFwCfgDmaBytes() so that it works
through a pointer, but without other (functionality) changes:

  volatile FW_CFG_DMA_ACCESS LocalAccess;
  volatile FW_CFG_DMA_ACCESS *Access;

  Access = &LocalAccess;

Second, add the SEV-specific prologue / epilogue that initially set the
"Access" pointer differently, and finally free / unmap it.

> in case
> of SEV the Dma "Access" control variable need to be dynamically allocated
> because hypervisor read/writes data into Access->status.
> 
> I could convert Access into FW_CFG_DMA_ACCESS pointer for non SEV case and
> then integerate the SEV specific changes inside the same function.

Yes, that's the idea.

> 
> I was just not sure which approach is prefrered hence decided to create a
> new function for now and at least start the discussion.

Thank you.
Laszlo

> 
> 
> 
> 
>> ... From skimming this patch, I think those are the only
>> functionality-related comments I have at this point, beyond the remarks
>> I made elsewhere in this series (like: line length, DEBUG_* macros, and
>> so on). Please recheck all patches for those comments.
>>
>>
> I will revist all the patches and fix those DEBUG_* macros.
> 
> 
> 
>>>
>>> diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
>> b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
>>> index ac05f4c..be8e945 100644
>>> --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
>>> +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
>>> @@ -4,6 +4,7 @@
>>>
>>>    Copyright (C) 2013, Red Hat, Inc.
>>>    Copyright (c) 2011 - 2013, Intel Corporation. All rights reserved.<BR>
>>> +  Copyright (c) 2017, Advanced Micro Devices. All rights reserved.<BR>
>>>
>>>    This program and the accompanying materials are licensed and made
>> available
>>>    under the terms and conditions of the BSD License which accompanies
>> this
>>> @@ -14,14 +15,34 @@
>>>    WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
>>>  **/
>>>
>>> +#include "Uefi.h"
>>> +
>>> +#include <Library/BaseLib.h>
>>>  #include <Library/DebugLib.h>
>>>  #include <Library/QemuFwCfgLib.h>
>>> +#include <Library/UefiBootServicesTableLib.h>
>>> +#include <Library/MemEncryptSevLib.h>
>>> +#include <Library/BmDmaLib.h>
>>>
>>>  #include "QemuFwCfgLibInternal.h"
>>>
>>>  STATIC BOOLEAN mQemuFwCfgSupported = FALSE;
>>>  STATIC BOOLEAN mQemuFwCfgDmaSupported;
>>> +STATIC BOOLEAN mQemuFwCfgSevIsEnabled = FALSE;
>>> +
>>> +/**
>>> + Returns a boolean indicating whether the SEV is enabled
>>>
>>> + @retval    TRUE    SEV is enabled
>>> + @retval    FALSE   SEV is not enabled
>>> +**/
>>> +BOOLEAN
>>> +InternalQemuFwCfgSevIsEnabled (
>>> +  VOID
>>> +  )
>>> +{
>>> +  return mQemuFwCfgSevIsEnabled;
>>> +}
>>>
>>>  /**
>>>    Returns a boolean indicating if the firmware configuration interface
>>> @@ -79,6 +100,9 @@ QemuFwCfgInitialize (
>>>      mQemuFwCfgDmaSupported = TRUE;
>>>      DEBUG ((DEBUG_INFO, "QemuFwCfg interface (DMA) is supported.\n"));
>>>    }
>>> +
>>> +  mQemuFwCfgSevIsEnabled = MemEncryptSevIsEnabled ();
>>> +
>>>    return RETURN_SUCCESS;
>>>  }
>>>
>>> @@ -114,3 +138,52 @@ InternalQemuFwCfgDmaIsAvailable (
>>>  {
>>>    return mQemuFwCfgDmaSupported;
>>>  }
>>> +
>>> +/**
>>> + Allocate a bounce buffer for SEV DMA.
>>> +
>>
>> Please document that this function either succeeds or doesn't return.
>>
>>> +  @param[in]     NumPage  Number of pages.
>>> +  @param[out]    Buffer   Allocated DMA Buffer pointer
>>> +
>>> +**/
>>> +VOID
>>> +InternalQemuFwCfgSevDmaAllocateBuffer (
>>> +  IN     UINT32   NumPages,
>>> +  OUT    VOID     **Buffer
>>> +  )
>>> +{
>>> +  EFI_STATUS  Status;
>>> +
>>> +  //
>>> +  // Allocate DMA bounce buffer
>>> +  //
>>> +  Status = BmDmaAllocateBuffer (TRUE, EfiBootServicesData, NumPages,
>> Buffer);
>>> +  if (EFI_ERROR(Status)) {
>>> +    DEBUG ((EFI_D_ERROR, "SEV: Failed to allocate bounce buffer %d
>> pages\n", NumPages));
>>> +    ASSERT_EFI_ERROR (Status);
>>> +    CpuDeadLoop ();
>>> +  }
>>> +
>>> +  DEBUG ((EFI_D_VERBOSE, "QemuFwCfgSevDma allocate buffer 0x%Lx Pages
>> %d\n", (UINTN)Buffer, NumPages));
>>> +}
>>> +
>>> +/**
>>> + Free the DMA buffer allocated using InternalQemuFwCfgSevDmaAllocat
>> eBuffer
>>> +
>>> +  @param[in]     NumPage  Number of pages.
>>> +  @param[in]     Buffer   DMA Buffer pointer
>>> +
>>> +**/
>>> +VOID
>>> +InternalQemuFwCfgSevDmaFreeBuffer (
>>> +  IN     VOID     *Buffer,
>>> +  IN     UINT32   NumPages
>>> +  )
>>> +{
>>> +  //
>>> +  // Free the bounce buffer
>>> +  //
>>> +  DEBUG ((EFI_D_VERBOSE, "QemuFwCfgSevDma free buffer 0x%Lx Pages
>> %d\n", (UINTN)Buffer, NumPages));
>>> +  BmDmaFreeBuffer (Buffer, NumPages);
>>> +}
>>> +
>>> diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
>> b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
>>> index 346bb88..536887f 100644
>>> --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
>>> +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
>>> @@ -47,4 +47,6 @@
>>>    DebugLib
>>>    IoLib
>>>    MemoryAllocationLib
>>> +  MemEncryptSevLib
>>> +  BmDmaLib
>>>
>>> diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
>> b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
>>> index 1bf725d..d2560a3 100644
>>> --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
>>> +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c
>>> @@ -47,6 +47,111 @@ QemuFwCfgSelectItem (
>>>
>>>
>>>  /**
>>> +  Transfer an array of bytes, or skip a number of bytes, using the SEV
>> DMA bounce
>>> +  interface. The function is same as InternalQemuFwCfgDmaBytes with
>> excpetion that
>>> +  it uses bounce buffer
>>> +
>>> +  @param[in]     Size     Size in bytes to transfer or skip.
>>> +
>>> +  @param[in,out] HostBuffer Buffer to read data into or write data
>> from. Ignored,
>>> +                            and may be NULL, if Size is zero, or
>> Control is
>>> +                            FW_CFG_DMA_CTL_SKIP.
>>> +
>>> +  @param[in]     Control  One of the following:
>>> +                          FW_CFG_DMA_CTL_WRITE - write to fw_cfg from
>> Buffer.
>>> +                          FW_CFG_DMA_CTL_READ  - read from fw_cfg into
>> Buffer.
>>> +                          FW_CFG_DMA_CTL_SKIP  - skip bytes in fw_cfg.
>>> +**/
>>> +VOID
>>> +InternalQemuFwCfgSevDmaBytes (
>>> +  IN     UINT32   Size,
>>> +  IN OUT VOID     *HostBuffer OPTIONAL,
>>> +  IN     UINT32   Control
>>> +  )
>>> +{
>>> +  volatile FW_CFG_DMA_ACCESS *Access;
>>> +  UINT32                     AccessHigh, AccessLow;
>>> +  UINT32                     Status;
>>> +  UINT32                     NumPages;
>>> +  VOID                       *DmaBuffer, *Buffer;
>>> +
>>> +  //
>>> +  // Calculate number of pages we need to allocate for this operation
>>> +  //
>>> +  if (Control == FW_CFG_DMA_CTL_SKIP) {
>>> +    //
>>> +    // Control data does not need the actual buffer
>>> +    //
>>> +    NumPages = EFI_SIZE_TO_PAGES (sizeof (*Access));
>>> +  } else {
>>> +    NumPages = EFI_SIZE_TO_PAGES (sizeof (*Access) + Size);
>>> +  }
>>> +
>>> +  //
>>> +  // Allocate DMA bounce buffer
>>> +  //
>>> +  InternalQemuFwCfgSevDmaAllocateBuffer (NumPages, &DmaBuffer);
>>> +
>>> +  Access = (FW_CFG_DMA_ACCESS *)DmaBuffer;
>>> +  Buffer = DmaBuffer + sizeof(*Access);
>>> +
>>> +  Access->Control = SwapBytes32 (Control);
>>> +  Access->Length  = SwapBytes32 (Size);
>>> +  Access->Address = SwapBytes64 ((UINTN)Buffer);
>>> +
>>> +  //
>>> +  // Copy data from Host buffer into DMA buffer
>>> +  //
>>> +  if (HostBuffer && (Control == FW_CFG_DMA_CTL_WRITE)) {
>>> +    CopyMem (Buffer, HostBuffer, Size);
>>> +  }
>>> +
>>> +  //
>>> +  // Delimit the transfer from (a) modifications to Access, (b) in case
>> of a
>>> +  // write, from writes to Buffer by the caller.
>>> +  //
>>> +  MemoryFence ();
>>> +
>>> +  //
>>> +  // Start the transfer.
>>> +  //
>>> +  AccessHigh = (UINT32)RShiftU64 ((UINTN)Access, 32);
>>> +  AccessLow  = (UINT32)(UINTN)Access;
>>> +  IoWrite32 (FW_CFG_IO_DMA_ADDRESS,     SwapBytes32 (AccessHigh));
>>> +  IoWrite32 (FW_CFG_IO_DMA_ADDRESS + 4, SwapBytes32 (AccessLow));
>>> +
>>> +  //
>>> +  // Don't look at Access->Control before starting the transfer.
>>> +  //
>>> +  MemoryFence ();
>>> +
>>> +  //
>>> +  // Wait for the transfer to complete.
>>> +  //
>>> +  do {
>>> +    Status = SwapBytes32 (Access->Control);
>>> +    ASSERT ((Status & FW_CFG_DMA_CTL_ERROR) == 0);
>>> +  } while (Status != 0);
>>> +
>>> +  //
>>> +  // After a read, the caller will want to use Buffer.
>>> +  //
>>> +  MemoryFence ();
>>> +
>>> +  //
>>> +  // Copy data from DMA buffer into Host Buffer
>>> +  //
>>> +  if (HostBuffer && (Control == FW_CFG_DMA_CTL_READ)) {
>>> +    CopyMem (HostBuffer, Buffer, Size);
>>> +  }
>>> +
>>> +  //
>>> +  // Free the DMA bounce buffer
>>> +  //
>>> +  InternalQemuFwCfgSevDmaFreeBuffer (DmaBuffer, NumPages);
>>> +}
>>> +
>>> +/**
>>>    Transfer an array of bytes, or skip a number of bytes, using the DMA
>>>    interface.
>>>
>>> @@ -79,6 +184,13 @@ InternalQemuFwCfgDmaBytes (
>>>      return;
>>>    }
>>>
>>> +  //
>>> +  // When SEV is enabled then use SEV version of DmaReadWrite
>>> +  //
>>> +  if (InternalQemuFwCfgSevIsEnabled ()) {
>>> +    return InternalQemuFwCfgSevDmaBytes (Size, Buffer, Control);
>>> +  }
>>> +
>>>    Access.Control = SwapBytes32 (Control);
>>>    Access.Length  = SwapBytes32 (Size);
>>>    Access.Address = SwapBytes64 ((UINTN)Buffer);
>>> diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLibInternal.h
>> b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLibInternal.h
>>> index 6e87c62..8e2ff45 100644
>>> --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLibInternal.h
>>> +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLibInternal.h
>>> @@ -2,6 +2,7 @@
>>>    Internal interfaces specific to the QemuFwCfgLib instances in OvmfPkg.
>>>
>>>    Copyright (C) 2016, Red Hat, Inc.
>>> +  Copyright (C) 2017, Advanced Micro Devices.
>>>
>>>    This program and the accompanying materials are licensed and made
>> available
>>>    under the terms and conditions of the BSD License which accompanies
>> this
>>> @@ -43,4 +44,41 @@ InternalQemuFwCfgDmaIsAvailable (
>>>    VOID
>>>    );
>>>
>>> +/**
>>> + Returns a boolean indicating whether the SEV is enabled
>>> +
>>> + @retval    TRUE    SEV is enabled
>>> + @retval    FALSE   SEV is not enabled
>>> +**/
>>> +BOOLEAN
>>> +InternalQemuFwCfgSevIsEnabled (
>>> +  VOID
>>> +  );
>>> +
>>> +/**
>>> + Allocate a bounce buffer for SEV DMA.
>>> +
>>> +  @param[in]     NumPage  Number of pages.
>>> +  @param[out]    Buffer   Allocated DMA Buffer pointer
>>> +
>>> +**/
>>> +VOID
>>> +InternalQemuFwCfgSevDmaAllocateBuffer (
>>> +  IN     UINT32   NumPages,
>>> +  OUT    VOID     **Buffer
>>> +  );
>>> +
>>> +/**
>>> + Free the DMA buffer allocated using InternalQemuFwCfgSevDmaAllocat
>> eBuffer
>>> +
>>> +  @param[in]     NumPage  Number of pages.
>>> +  @param[in]     Buffer   DMA Buffer pointer
>>> +
>>> +**/
>>> +VOID
>>> +InternalQemuFwCfgSevDmaFreeBuffer (
>>> +  IN     VOID     *Buffer,
>>> +  IN     UINT32   NumPages
>>> +  );
>>> +
>>>  #endif
>>> diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
>> b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
>>> index ac05f4c..3dc9270 100644
>>> --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
>>> +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
>>> @@ -4,6 +4,7 @@
>>>
>>>    Copyright (C) 2013, Red Hat, Inc.
>>>    Copyright (c) 2011 - 2013, Intel Corporation. All rights reserved.<BR>
>>> +  Copyright (c) 2017, Advanced Micro Devices. All rights reserved.<BR>
>>>
>>>    This program and the accompanying materials are licensed and made
>> available
>>>    under the terms and conditions of the BSD License which accompanies
>> this
>>> @@ -14,14 +15,55 @@
>>>    WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
>>>  **/
>>>
>>> +#include <Library/BaseLib.h>
>>>  #include <Library/DebugLib.h>
>>>  #include <Library/QemuFwCfgLib.h>
>>> +#include <Register/Cpuid.h>
>>> +#include <Register/AmdSevMap.h>
>>>
>>>  #include "QemuFwCfgLibInternal.h"
>>>
>>>  STATIC BOOLEAN mQemuFwCfgSupported = FALSE;
>>>  STATIC BOOLEAN mQemuFwCfgDmaSupported;
>>>
>>> +/**
>>> + Returns a boolean indicating whether the SEV is enabled
>>> +
>>> + @retval    TRUE    SEV is enabled
>>> + @retval    FALSE   SEV is not enabled
>>> +**/
>>> +BOOLEAN
>>> +InternalQemuFwCfgSevIsEnabled (
>>> +  VOID
>>> +  )
>>> +{
>>> +  UINT32 RegEax;
>>> +  MSR_SEV_STATUS_REGISTER Msr;
>>> +  CPUID_MEMORY_ENCRYPTION_INFO_EAX  Eax;
>>> +
>>> +  //
>>> +  // Check if memory encryption leaf exist
>>> +  //
>>> +  AsmCpuid (CPUID_EXTENDED_FUNCTION, &RegEax, NULL, NULL, NULL);
>>> +  if (RegEax >= CPUID_MEMORY_ENCRYPTION_INFO) {
>>> +    //
>>> +    // CPUID Fn8000_001F[EAX] Bit 1 (Sev supported)
>>> +    //
>>> +    AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, &Eax.Uint32, NULL, NULL,
>> NULL);
>>> +
>>> +    if (Eax.Bits.SevBit) {
>>> +      //
>>> +      // Check MSR_0xC0010131 Bit 0 (Sev Enabled)
>>> +      //
>>> +      Msr.Uint32 = AsmReadMsr32 (MSR_SEV_STATUS);
>>> +      if (Msr.Bits.SevBit) {
>>> +        return TRUE;
>>> +      }
>>> +    }
>>> +  }
>>> +
>>> +  return FALSE;
>>> +}
>>>
>>>  /**
>>>    Returns a boolean indicating if the firmware configuration interface
>>> @@ -79,6 +121,17 @@ QemuFwCfgInitialize (
>>>      mQemuFwCfgDmaSupported = TRUE;
>>>      DEBUG ((DEBUG_INFO, "QemuFwCfg interface (DMA) is supported.\n"));
>>>    }
>>> +
>>> +  //
>>> +  // When SEV is enabled then we do not support DMA interface.
>>> +  // This is because we need to use bounce buffer to support DMA
>> operation in SEV guest.
>>> +  // Allocating memory for bounce buffer can get painful in Pei phase
>>> +  //
>>> +  if (mQemuFwCfgDmaSupported && InternalQemuFwCfgSevIsEnabled ()) {
>>> +    mQemuFwCfgDmaSupported = FALSE;
>>> +    DEBUG ((DEBUG_INFO, "QemuFwCfg disabling DMA interface and
>> defaulting to IO Port.\n"));
>>> +  }
>>> +
>>>    return RETURN_SUCCESS;
>>>  }
>>>
>>> @@ -114,3 +167,43 @@ InternalQemuFwCfgDmaIsAvailable (
>>>  {
>>>    return mQemuFwCfgDmaSupported;
>>>  }
>>> +
>>> +/**
>>> + Allocate a bounce buffer for SEV DMA.
>>> +
>>> +  @param[in]     NumPage  Number of pages.
>>> +  @param[out]    Buffer   Allocated DMA Buffer pointer
>>> +
>>> +**/
>>> +VOID
>>> +InternalQemuFwCfgSevDmaAllocateBuffer (
>>> +  IN     UINT32   NumPages,
>>> +  OUT    VOID     **Buffer
>>> +  )
>>> +{
>>> +  //
>>> +  // We should never reach here
>>> +  //
>>> +  ASSERT (FALSE);
>>> +  CpuDeadLoop ();
>>> +}
>>> +
>>> +/**
>>> + Free the DMA buffer allocated using InternalQemuFwCfgSevDmaAllocat
>> eBuffer
>>> +
>>> +  @param[in]     NumPage  Number of pages.
>>> +  @param[in]     Buffer   DMA Buffer pointer
>>> +
>>> +**/
>>> +VOID
>>> +InternalQemuFwCfgSevDmaFreeBuffer (
>>> +  IN     VOID     *Buffer,
>>> +  IN     UINT32   NumPages
>>> +  )
>>> +{
>>> +  //
>>> +  // We should never reach here
>>> +  //
>>> +  ASSERT (FALSE);
>>> +  CpuDeadLoop ();
>>> +}
>>> diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
>> b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
>>> index 4f966a8..83cc0de 100644
>>> --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
>>> +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
>>> @@ -39,7 +39,9 @@
>>>
>>>  [Packages]
>>>    MdePkg/MdePkg.dec
>>> +  MdeModulePkg/MdeModulePkg.dec
>>>    OvmfPkg/OvmfPkg.dec
>>> +  UefiCpuPkg/UefiCpuPkg.dec
>>>
>>>  [LibraryClasses]
>>>    BaseLib
>>> diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSec.c
>> b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSec.c
>>> index 465ccbe..70b0a47 100644
>>> --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSec.c
>>> +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSec.c
>>> @@ -16,8 +16,11 @@
>>>    WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
>>>  **/
>>>
>>> +#include <Library/BaseLib.h>
>>>  #include <Library/DebugLib.h>
>>>  #include <Library/QemuFwCfgLib.h>
>>> +#include <Register/Cpuid.h>
>>> +#include <Register/AmdSevMap.h>
>>>
>>>  #include "QemuFwCfgLibInternal.h"
>>>
>>> @@ -94,3 +97,82 @@ InternalQemuFwCfgDmaIsAvailable (
>>>  {
>>>    return FALSE;
>>>  }
>>> +
>>> +/**
>>> + Returns a boolean indicating whether the SEV is enabled
>>> +
>>> + @retval    TRUE    SEV is enabled
>>> + @retval    FALSE   SEV is not enabled
>>> +**/
>>> +BOOLEAN
>>> +InternalQemuFwCfgSevIsEnabled (
>>> +  VOID
>>> +  )
>>> +{
>>> +  UINT32 RegEax;
>>> +  MSR_SEV_STATUS_REGISTER Msr;
>>> +  CPUID_MEMORY_ENCRYPTION_INFO_EAX  Eax;
>>> +
>>> +  //
>>> +  // Check if memory encryption leaf exist
>>> +  //
>>> +  AsmCpuid (CPUID_EXTENDED_FUNCTION, &RegEax, NULL, NULL, NULL);
>>> +  if (RegEax >= CPUID_MEMORY_ENCRYPTION_INFO) {
>>> +    //
>>> +    // CPUID Fn8000_001F[EAX] Bit 1 (Sev supported)
>>> +    //
>>> +    AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, &Eax.Uint32, NULL, NULL,
>> NULL);
>>> +
>>> +    if (Eax.Bits.SevBit) {
>>> +      //
>>> +      // Check MSR_0xC0010131 Bit 0 (Sev Enabled)
>>> +      //
>>> +      Msr.Uint32 = AsmReadMsr32 (MSR_SEV_STATUS);
>>> +      if (Msr.Bits.SevBit) {
>>> +        return TRUE;
>>> +      }
>>> +    }
>>> +  }
>>> +
>>> +  return FALSE;
>>> +}
>>> +
>>> +/**
>>> + Allocate a bounce buffer for SEV DMA.
>>> +
>>> +  @param[in]     NumPage  Number of pages.
>>> +  @param[out]    Buffer   Allocated DMA Buffer pointer
>>> +
>>> +**/
>>> +VOID
>>> +InternalQemuFwCfgSevDmaAllocateBuffer (
>>> +  IN     UINT32   NumPages,
>>> +  OUT    VOID     **Buffer
>>> +  )
>>> +{
>>> +  //
>>> +  // We should never reach here
>>> +  //
>>> +  ASSERT (FALSE);
>>> +  CpuDeadLoop ();
>>> +}
>>> +
>>> +/**
>>> + Free the DMA buffer allocated using InternalQemuFwCfgSevDmaAllocat
>> eBuffer
>>> +
>>> +  @param[in]     NumPage  Number of pages.
>>> +  @param[in]     Buffer   DMA Buffer pointer
>>> +
>>> +**/
>>> +VOID
>>> +InternalQemuFwCfgSevDmaFreeBuffer (
>>> +  IN     VOID     *Buffer,
>>> +  IN     UINT32   NumPages
>>> +  )
>>> +{
>>> +  //
>>> +  // We should never reach here
>>> +  //
>>> +  ASSERT (FALSE);
>>> +  CpuDeadLoop ();
>>> +}
>>>
>>> _______________________________________________
>>> edk2-devel mailing list
>>> edk2-devel@lists.01.org
>>> https://lists.01.org/mailman/listinfo/edk2-devel
>>>
>>
>>
> 
>