[PATCH v8 52/55] i386/tdx: Don't treat SYSCALL as unavailable

[Xiaoyao Li <xiaoyao.li@intel.com>]

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
---
Changes in v7:
 - fix CPUID_EXT2_SYSCALL by adding it to actual;
---
 target/i386/kvm/tdx.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index 58797470ba7e..cd8e96d476b8 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -841,6 +841,19 @@ static int tdx_check_features(X86ConfidentialGuest *cg, CPUState *cs)
             continue;
         }
 
+        /* Fixup for special cases */
+        switch (w) {
+        case FEAT_8000_0001_EDX:
+            /*
+             * Intel enumerates SYSCALL bit as 1 only when processor in 64-bit
+             * mode and before vcpu running it's not in 64-bit mode.
+             */
+            actual |= CPUID_EXT2_SYSCALL;
+            break;
+        default:
+            break;
+        }
+
         requested = env->features[w];
         unavailable = requested & ~actual;
         mark_unavailable_features(cpu, w, unavailable, unav_prefix);
-- 
2.34.1