[edk2-devel] [PATCH v10 10/32] OvmfPkg/SecMain: register GHCB gpa for the SEV-SNP guest
Brijesh Singh via groups.io
brijesh.singh=amd.com at groups.io
Tue Oct 19 19:39:12 UTC 2021
BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275
The SEV-SNP guest requires that GHCB GPA must be registered before using.
See the GHCB specification section 2.3.2 for more details.
Cc: Michael Roth <michael.roth at amd.com>
Cc: James Bottomley <jejb at linux.ibm.com>
Cc: Min Xu <min.m.xu at intel.com>
Cc: Jiewen Yao <jiewen.yao at intel.com>
Cc: Tom Lendacky <thomas.lendacky at amd.com>
Cc: Jordan Justen <jordan.l.justen at intel.com>
Cc: Ard Biesheuvel <ardb+tianocore at kernel.org>
Cc: Erdem Aktas <erdemaktas at google.com>
Cc: Gerd Hoffmann <kraxel at redhat.com>
Acked-by: Jiewen Yao <Jiewen.yao at intel.com>
Acked-by: Gerd Hoffmann <kraxel at redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh at amd.com>
---
OvmfPkg/Sec/AmdSev.c | 118 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 118 insertions(+)
diff --git a/OvmfPkg/Sec/AmdSev.c b/OvmfPkg/Sec/AmdSev.c
index 7f74e8bfe88e..9dd42b195785 100644
--- a/OvmfPkg/Sec/AmdSev.c
+++ b/OvmfPkg/Sec/AmdSev.c
@@ -48,6 +48,103 @@ SevEsProtocolFailure (
CpuDeadLoop ();
}
+/**
+ Determine if SEV-SNP is active.
+
+ @retval TRUE SEV-SNP is enabled
+ @retval FALSE SEV-SNP is not enabled
+
+**/
+STATIC
+BOOLEAN
+SevSnpIsEnabled (
+ VOID
+ )
+{
+ MSR_SEV_STATUS_REGISTER Msr;
+
+ //
+ // Read the SEV_STATUS MSR to determine whether SEV-SNP is active.
+ //
+ Msr.Uint32 = AsmReadMsr32 (MSR_SEV_STATUS);
+
+ //
+ // Check MSR_0xC0010131 Bit 2 (Sev-Snp Enabled)
+ //
+ if (Msr.Bits.SevSnpBit) {
+ return TRUE;
+ }
+
+ return FALSE;
+}
+
+/**
+ Register the GHCB GPA
+
+*/
+STATIC
+VOID
+SevSnpGhcbRegister (
+ UINTN Address
+ )
+{
+ MSR_SEV_ES_GHCB_REGISTER Msr;
+ EFI_PHYSICAL_ADDRESS GuestFrameNumber;
+
+ GuestFrameNumber = Address >> EFI_PAGE_SHIFT;
+
+ //
+ // Use the GHCB MSR Protocol to request to register the GPA.
+ //
+ Msr.GhcbPhysicalAddress = 0;
+ Msr.GhcbGpaRegister.Function = GHCB_INFO_GHCB_GPA_REGISTER_REQUEST;
+ Msr.GhcbGpaRegister.GuestFrameNumber = GuestFrameNumber;
+ AsmWriteMsr64 (MSR_SEV_ES_GHCB, Msr.GhcbPhysicalAddress);
+
+ AsmVmgExit ();
+
+ Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
+
+ //
+ // If hypervisor responded with a different GPA than requested then fail.
+ //
+ if ((Msr.GhcbGpaRegister.Function != GHCB_INFO_GHCB_GPA_REGISTER_RESPONSE) ||
+ (Msr.GhcbGpaRegister.GuestFrameNumber != GuestFrameNumber)) {
+ SevEsProtocolFailure (GHCB_TERMINATE_GHCB_GENERAL);
+ }
+}
+
+/**
+ Verify that Hypervisor supports the SNP feature.
+
+ */
+STATIC
+BOOLEAN
+HypervisorSnpFeatureCheck (
+ VOID
+ )
+{
+ MSR_SEV_ES_GHCB_REGISTER Msr;
+
+ //
+ // Use the GHCB MSR Protocol to query the hypervisor capabilities
+ //
+ Msr.GhcbPhysicalAddress = 0;
+ Msr.GhcbHypervisorFeatures.Function = GHCB_HYPERVISOR_FEATURES_REQUEST;
+ AsmWriteMsr64 (MSR_SEV_ES_GHCB, Msr.GhcbPhysicalAddress);
+
+ AsmVmgExit ();
+
+ Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
+
+ if ((Msr.GhcbHypervisorFeatures.Function != GHCB_HYPERVISOR_FEATURES_RESPONSE) ||
+ (!(Msr.GhcbHypervisorFeatures.Features & GHCB_HV_FEATURES_SNP))) {
+ return FALSE;
+ }
+
+ return TRUE;
+}
+
/**
Validate the SEV-ES/GHCB protocol level.
@@ -88,6 +185,27 @@ SevEsProtocolCheck (
SevEsProtocolFailure (GHCB_TERMINATE_GHCB_PROTOCOL);
}
+ //
+ // We cannot use the MemEncryptSevSnpIsEnabled () because the
+ // ProcessLibraryConstructorList () is not called yet.
+ //
+ if (SevSnpIsEnabled ()) {
+ //
+ // Check if hypervisor supports the SNP feature
+ //
+ if (!HypervisorSnpFeatureCheck ()) {
+ SevEsProtocolFailure (GHCB_TERMINATE_GHCB_PROTOCOL);
+ }
+
+ //
+ // Unlike the SEV-ES guest, the SNP requires that GHCB GPA must be
+ // registered with the Hypervisor before the use. This can be done
+ // using the new VMGEXIT defined in the GHCB v2. Register the GPA
+ // before it is used.
+ //
+ SevSnpGhcbRegister (FixedPcdGet32 (PcdOvmfSecGhcbBase));
+ }
+
//
// SEV-ES protocol checking succeeded, set the initial GHCB address
//
--
2.25.1
-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#82373): https://edk2.groups.io/g/devel/message/82373
Mute This Topic: https://groups.io/mt/86448808/1813853
Group Owner: devel+owner at edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/unsub [edk2-devel-archive at redhat.com]
-=-=-=-=-=-=-=-=-=-=-=-
More information about the edk2-devel-archive
mailing list