The SEV-ES DebugSwap feature enables type B swaping of debug registers
on #VMEXIT and makes #DB and DR7 intercepts unnecessary and unwanted.
When DebugSwap is enabled, this stops booting if #VC for #DB or
DB7 read/write occurs as this signals unwanted interaction from the HV.
This adds new API which uses SEV-ES working area in PEI and SEC.
This does not change the existing behavour for DXE just yet but soon.
Signed-off-by: Alexey Kardashevskiy <aik@...>
---
OvmfPkg/Include/Library/MemEncryptSevLib.h | 12 ++++++++++
OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLibInternal.c | 25 +++++++++++++++++---
OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLibInternal.c | 19 +++++++++++++++
OvmfPkg/Library/BaseMemEncryptSevLib/SecMemEncryptSevLibInternal.c | 20 ++++++++++++++++
OvmfPkg/Library/CcExitLib/CcExitVcHandler.c | 8 +++++++
5 files changed, 81 insertions(+), 3 deletions(-)
diff --git a/OvmfPkg/Include/Library/MemEncryptSevLib.h b/OvmfPkg/Include/Library/MemEncryptSevLib.h
index 4fa9c0d70083..0fa86aecc38c 100644
--- a/OvmfPkg/Include/Library/MemEncryptSevLib.h
+++ b/OvmfPkg/Include/Library/MemEncryptSevLib.h
@@ -166,6 +166,18 @@ MemEncryptSevGetEncryptionMask (
VOID
);
+/**
+ Returns a boolean to indicate whether DebugSwap is enabled.
+
+ @retval TRUE DebugSwap is enabled
+ @retval FALSE DebugSwap is not enabled
+**/
+BOOLEAN
+EFIAPI
+MemEncryptSevEsDebugSwapIsEnabled (
+ VOID
+ );
+
/**
Returns the encryption state of the specified virtual address range.
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLibInternal.c b/OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLibInternal.c
index 4aba0075b9e2..ffe5399c73ca 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLibInternal.c
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLibInternal.c
@@ -40,19 +40,23 @@ AmdMemEncryptionAttrCheck (
IN CONFIDENTIAL_COMPUTING_GUEST_ATTR Attr
)
{
+ UINT64 CurrentLevel = CurrentAttr & ~CCAttrAmdSevFeatureMask;
+
switch (Attr) {
case CCAttrAmdSev:
//
// SEV is automatically enabled if SEV-ES or SEV-SNP is active.
//
- return CurrentAttr >= CCAttrAmdSev;
+ return CurrentLevel >= CCAttrAmdSev;
case CCAttrAmdSevEs:
//
// SEV-ES is automatically enabled if SEV-SNP is active.
//
- return CurrentAttr >= CCAttrAmdSevEs;
+ return CurrentLevel >= CCAttrAmdSevEs;
case CCAttrAmdSevSnp:
- return CurrentAttr == CCAttrAmdSevSnp;
+ return CurrentLevel == CCAttrAmdSevSnp;
+ case CCAttrAmdSevFeatureDebugSwap:
+ return !!(CurrentAttr & CCAttrAmdSevFeatureDebugSwap);
default:
return FALSE;
}
@@ -159,3 +163,18 @@ MemEncryptSevGetEncryptionMask (
return mSevEncryptionMask;
}
+
+/**
+ Returns a boolean to indicate whether DebugSwap is enabled.
+
+ @retval TRUE DebugSwap is enabled
+ @retval FALSE DebugSwap is not enabled
+**/
+BOOLEAN
+EFIAPI
+MemEncryptSevEsDebugSwapIsEnabled (
+ VOID
+ )
+{
+ return ConfidentialComputingGuestHas (CCAttrAmdSevFeatureDebugSwap);
+}
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLibInternal.c b/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLibInternal.c
index 41d1246a5b31..e2ebc8afcaee 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLibInternal.c
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/PeiMemEncryptSevLibInternal.c
@@ -141,3 +141,22 @@ MemEncryptSevGetEncryptionMask (
return SevEsWorkArea->EncryptionMask;
}
+
+/**
+ Returns a boolean to indicate whether DebugSwap is enabled.
+
+ @retval TRUE DebugSwap is enabled
+ @retval FALSE DebugSwap is not enabled
+**/
+BOOLEAN
+EFIAPI
+MemEncryptSevEsDebugSwapIsEnabled (
+ VOID
+ )
+{
+ MSR_SEV_STATUS_REGISTER Msr;
+
+ Msr.Uint32 = InternalMemEncryptSevStatus ();
+
+ return Msr.Bits.DebugSwap ? TRUE : FALSE;
+}
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/SecMemEncryptSevLibInternal.c b/OvmfPkg/Library/BaseMemEncryptSevLib/SecMemEncryptSevLibInternal.c
index 27148c7e337a..974be9555296 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/SecMemEncryptSevLibInternal.c
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/SecMemEncryptSevLibInternal.c
@@ -142,6 +142,26 @@ MemEncryptSevGetEncryptionMask (
return SevEsWorkArea->EncryptionMask;
}
+
+/**
+ Returns a boolean to indicate whether DebugSwap is enabled.
+
+ @retval TRUE DebugSwap is enabled
+ @retval FALSE DebugSwap is not enabled
+**/
+BOOLEAN
+EFIAPI
+MemEncryptSevEsDebugSwapIsEnabled (
+ VOID
+ )
+{
+ MSR_SEV_STATUS_REGISTER Msr;
+
+ Msr.Uint32 = InternalMemEncryptSevStatus ();
+
+ return Msr.Bits.DebugSwap ? TRUE : FALSE;
+}
+
/**
Locate the page range that covers the initial (pre-SMBASE-relocation) SMRAM
Save State Map.
diff --git a/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c b/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
index 985e5479775c..811cad164ea2 100644
--- a/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
+++ b/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
@@ -2136,6 +2136,10 @@ Dr7WriteExit (
UINT64 *Register;
UINT64 Status;
+ if (MemEncryptSevEsDebugSwapIsEnabled ()) {
+ return UnsupportedExit (Ghcb, Regs, InstructionData);
+ }
+
Ext = &InstructionData->Ext;
SevEsData = (SEV_ES_PER_CPU_DATA *)(Ghcb + 1);
@@ -2188,6 +2192,10 @@ Dr7ReadExit (
SEV_ES_PER_CPU_DATA *SevEsData;
UINT64 *Register;
+ if (MemEncryptSevEsDebugSwapIsEnabled ()) {
+ return UnsupportedExit (Ghcb, Regs, InstructionData);
+ }
+
Ext = &InstructionData->Ext;
SevEsData = (SEV_ES_PER_CPU_DATA *)(Ghcb + 1);
--
2.38.1
