diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SecSnpSystemRamValidate.c b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SecSnpSystemRamValidate.c index bc891c2636..7797febb8a 100644 --- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SecSnpSystemRamValidate.c +++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SecSnpSystemRamValidate.c @@ -14,6 +14,43 @@ #include "SnpPageStateChange.h" +// +// The variable used for the VMPL check. +// +STATIC UINT8 gVmpl0Data[4096]; + +/** + The function checks whether SEV-SNP guest is booted under VMPL0. + + @retval TRUE The guest is booted under VMPL0 + @retval FALSE The guest is not booted under VMPL0 + **/ +STATIC +BOOLEAN +SevSnpIsVmpl0 ( + VOID + ) +{ + UINT64 Rdx; + EFI_STATUS Status; + + // + // There is no straightforward way to query the current VMPL level. + // The simplest method is to use the RMPADJUST instruction to change + // a page permission to a VMPL level-1, and if the guest kernel is + // launched at a level <= 1, then RMPADJUST instruction will return + // an error. + // + Rdx = 1; + + Status = AsmRmpAdjust ((UINT64)gVmpl0Data, 0, Rdx); + if (EFI_ERROR (Status)) { + return FALSE; + } + + return TRUE; +} + /** Pre-validate the system RAM when SEV-SNP is enabled in the guest VM. @@ -32,5 +69,14 @@ MemEncryptSevSnpPreValidateSystemRam ( return; } + // + // The page state change uses the PVALIDATE instruction. The instruction + // can be run on VMPL-0 only. If its not VMPL-0 guest then terminate + // the boot. + // + if (!SevSnpIsVmpl0 ()) { + SnpPageStateFailureTerminate (); + } + InternalSetPageState (BaseAddress, NumPages, SevSnpPagePrivate, TRUE); } diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChange.h b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChange.h index b396f0ffbd..43319cc9ed 100644 --- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChange.h +++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChange.h @@ -27,4 +27,9 @@ InternalSetPageState ( IN BOOLEAN UseLargeEntry ); +VOID +SnpPageStateFailureTerminate ( + VOID + ); + #endif diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChangeInternal.c b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChangeInternal.c index 9c552ef5c7..d11aafae84 100644 --- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChangeInternal.c +++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/SnpPageStateChangeInternal.c @@ -42,7 +42,6 @@ MemoryStateToGhcbOp ( return Cmd; } -STATIC VOID SnpPageStateFailureTerminate ( VOID