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

[Brijesh Singh <brijesh.ksingh@gmail.com>]

The patch adds SEV support in QemuFwCfgLib. When SEV is enabled:

 * Pei phase support IO-style operations. This is mainly because we need to
   use a bounce buffer inorder to support DMA operation. Allocate a memory
   for bounce buffer can get painful in Pei phase hence if we detect FWCfg DMA
   support then silently fallback to IO.

* Dxe phase supports both IO and DMA style operations.
---
 OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c        |   73 +++++++++++++
 OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf   |    2 
 OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgLib.c        |  112 ++++++++++++++++++++
 .../Library/QemuFwCfgLib/QemuFwCfgLibInternal.h    |   38 +++++++
 OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c        |   93 +++++++++++++++++
 OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf   |    2 
 OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSec.c        |   82 +++++++++++++++
 7 files changed, 402 insertions(+)

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.
+
+  @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 InternalQemuFwCfgSevDmaAllocateBuffer
+
+  @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 InternalQemuFwCfgSevDmaAllocateBuffer
+
+  @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 InternalQemuFwCfgSevDmaAllocateBuffer
+
+  @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 InternalQemuFwCfgSevDmaAllocateBuffer
+
+  @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 ();
+}