Align with IGVM files providing SEV features with
SVM_SEV_FEAT_SNP_ACTIVE set by setting the same when creating a
sev-snp-guest object.

Since KVM sets this feature itself, SVM_SEV_FEAT_SNP_ACTIVE is unset
before KVM_SEV_INIT2 ioctl is invoked. Move that out of IGVM-specific
section to common code.

While at it, convert the existing SVM_SEV_FEAT_SNP_ACTIVE definition to
use the BIT() macro for consistency with upcoming feature flags.

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Naveen N Rao (AMD) <naveen@kernel.org>
---
 target/i386/sev.h |  2 +-
 target/i386/sev.c | 24 +++++++++++++++++-------
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/target/i386/sev.h b/target/i386/sev.h
index 9db1a802f6bb..102546b112d6 100644
--- a/target/i386/sev.h
+++ b/target/i386/sev.h
@@ -44,7 +44,7 @@ bool sev_snp_enabled(void);
 #define SEV_SNP_POLICY_SMT      0x10000
 #define SEV_SNP_POLICY_DBG      0x80000
 
-#define SVM_SEV_FEAT_SNP_ACTIVE 1
+#define SVM_SEV_FEAT_SNP_ACTIVE     BIT(0)
 
 typedef struct SevKernelLoaderContext {
     char *setup_data;
diff --git a/target/i386/sev.c b/target/i386/sev.c
index 1057b8ab2c60..2fb1268ed788 100644
--- a/target/i386/sev.c
+++ b/target/i386/sev.c
@@ -319,6 +319,15 @@ sev_set_guest_state(SevCommonState *sev_common, SevState new_state)
     sev_common->state = new_state;
 }
 
+static void sev_set_feature(SevCommonState *sev_common, uint64_t feature, bool set)
+{
+    if (set) {
+        sev_common->sev_features |= feature;
+    } else {
+        sev_common->sev_features &= ~feature;
+    }
+}
+
 static void
 sev_ram_block_added(RAMBlockNotifier *n, void *host, size_t size,
                     size_t max_size)
@@ -1897,15 +1906,15 @@ static int sev_common_kvm_init(ConfidentialGuestSupport *cgs, Error **errp)
                 -1) {
                 return -1;
             }
-            /*
-             * KVM maintains a bitmask of allowed sev_features. This does not
-             * include SVM_SEV_FEAT_SNP_ACTIVE which is set accordingly by KVM
-             * itself. Therefore we need to clear this flag.
-             */
-            args.vmsa_features = sev_common->sev_features &
-                                 ~SVM_SEV_FEAT_SNP_ACTIVE;
         }
 
+        /*
+         * KVM maintains a bitmask of allowed sev_features. This does not
+         * include SVM_SEV_FEAT_SNP_ACTIVE which is set accordingly by KVM
+         * itself. Therefore we need to clear this flag.
+         */
+        args.vmsa_features = sev_common->sev_features & ~SVM_SEV_FEAT_SNP_ACTIVE;
+
         ret = sev_ioctl(sev_common->sev_fd, KVM_SEV_INIT2, &args, &fw_error);
         break;
     }
@@ -3127,6 +3136,7 @@ sev_snp_guest_instance_init(Object *obj)
 
     /* default init/start/finish params for kvm */
     sev_snp_guest->kvm_start_conf.policy = DEFAULT_SEV_SNP_POLICY;
+    sev_set_feature(SEV_COMMON(sev_snp_guest), SVM_SEV_FEAT_SNP_ACTIVE, true);
 }
 
 /* guest info specific to sev-snp */
-- 
2.51.0