[PATCH 7/8] target/i386: SEV: Add support for enabling Secure TSC SEV feature

[Naveen N Rao (AMD)]

Add support for enabling Secure TSC VMSA SEV feature in SEV-SNP guests
through a new "secure-tsc" boolean property on SEV-SNP guest objects. By
default, KVM uses the host TSC frequency for Secure TSC.

Sample command-line:
  -machine q35,confidential-guest-support=sev0 \
  -object sev-snp-guest,id=sev0,cbitpos=51,reduced-phys-bits=1,secure-tsc=on

Co-developed-by: Ketan Chaturvedi <ketan.chaturv...@amd.com>
Signed-off-by: Ketan Chaturvedi <ketan.chaturv...@amd.com>
Co-developed-by: Nikunj A Dadhania <nik...@amd.com>
Signed-off-by: Nikunj A Dadhania <nik...@amd.com>
Signed-off-by: Naveen N Rao (AMD) <nav...@kernel.org>
---
 target/i386/sev.h |  1 +
 target/i386/sev.c | 13 +++++++++++++
 qapi/qom.json     |  6 +++++-
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/target/i386/sev.h b/target/i386/sev.h
index 8e09b2ce1976..87e73034ad15 100644
--- a/target/i386/sev.h
+++ b/target/i386/sev.h
@@ -46,6 +46,7 @@ bool sev_snp_enabled(void);
 
 #define SVM_SEV_FEAT_SNP_ACTIVE     BIT(0)
 #define SVM_SEV_FEAT_DEBUG_SWAP     BIT(5)
+#define SVM_SEV_FEAT_SECURE_TSC     BIT(9)
 
 typedef struct SevKernelLoaderContext {
     char *setup_data;
diff --git a/target/i386/sev.c b/target/i386/sev.c
index 6b11359f06dd..679bedb63c3a 100644
--- a/target/i386/sev.c
+++ b/target/i386/sev.c
@@ -3117,6 +3117,16 @@ sev_snp_guest_set_host_data(Object *obj, const char 
*value, Error **errp)
     memcpy(finish->host_data, blob, len);
 }
 
+static bool sev_snp_guest_get_secure_tsc(Object *obj, Error **errp)
+{
+    return is_sev_feature_set(SEV_COMMON(obj), SVM_SEV_FEAT_SECURE_TSC);
+}
+
+static void sev_snp_guest_set_secure_tsc(Object *obj, bool value, Error **errp)
+{
+    sev_set_feature(SEV_COMMON(obj), SVM_SEV_FEAT_SECURE_TSC, value);
+}
+
 static void
 sev_snp_guest_class_init(ObjectClass *oc, const void *data)
 {
@@ -3152,6 +3162,9 @@ sev_snp_guest_class_init(ObjectClass *oc, const void 
*data)
     object_class_property_add_str(oc, "host-data",
                                   sev_snp_guest_get_host_data,
                                   sev_snp_guest_set_host_data);
+    object_class_property_add_bool(oc, "secure-tsc",
+                                  sev_snp_guest_get_secure_tsc,
+                                  sev_snp_guest_set_secure_tsc);
 }
 
 static void
diff --git a/qapi/qom.json b/qapi/qom.json
index df962d4a5215..52c23e85e349 100644
--- a/qapi/qom.json
+++ b/qapi/qom.json
@@ -1100,6 +1100,9 @@
 #     firmware.  Set this to true to disable the use of VCEK.
 #     (default: false) (since: 9.1)
 #
+# @secure-tsc: enable Secure TSC
+#     (default: false) (since 10.2)
+#
 # Since: 9.1
 ##
 { 'struct': 'SevSnpGuestProperties',
@@ -1111,7 +1114,8 @@
             '*id-auth': 'str',
             '*author-key-enabled': 'bool',
             '*host-data': 'str',
-            '*vcek-disabled': 'bool' } }
+            '*vcek-disabled': 'bool',
+            '*secure-tsc': 'bool' } }
 
 ##
 # @TdxGuestProperties:
-- 
2.51.0