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| author | Brijesh Singh via groups.io <brijesh.singh=amd.com@groups.io> | 2021-12-09 11:27:43 +0800 |
|---|---|---|
| committer | mergify[bot] <37929162+mergify[bot]@users.noreply.github.com> | 2021-12-09 06:28:10 +0000 |
| commit | d706f8fec256585de76280d2a1e1aa9550cefe12 (patch) | |
| tree | 0c545b9df216c94d3981472e2ac2002e53ae8739 /OvmfPkg | |
| parent | ade62c18f4742301bbef474ac10518bde5972fba (diff) | |
| download | edk2-d706f8fec256585de76280d2a1e1aa9550cefe12.tar.gz edk2-d706f8fec256585de76280d2a1e1aa9550cefe12.tar.bz2 edk2-d706f8fec256585de76280d2a1e1aa9550cefe12.zip | |
OvmfPkg/MemEncryptSevLib: add function to check the VMPL0
BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275
Virtual Machine Privilege Level (VMPL) feature in the SEV-SNP
architecture allows a guest VM to divide its address space into four
levels. The level can be used to provide the hardware isolated
abstraction layers with a VM. The VMPL0 is the highest privilege, and
VMPL3 is the least privilege. Certain operations must be done by the
VMPL0 software, such as:
* Validate or invalidate memory range (PVALIDATE instruction)
* Allocate VMSA page (RMPADJUST instruction when VMSA=1)
The initial SEV-SNP support assumes that the guest is running on VMPL0.
Let's add function in the MemEncryptSevLib that can be used for checking
whether guest is booted under the VMPL0.
Cc: Michael Roth <michael.roth@amd.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Diffstat (limited to 'OvmfPkg')
3 files changed, 51 insertions, 1 deletions
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
|