fix(test): Add invpcid_single to guest-host feature diff on ubuntu

Linux kernel v6.6+ drops the synthetic feature flag. While our ubuntu
host kernel is v6.8 that has the change, Amazon Linux kernels and our
guest kernel doesn't.

Fixes: 4e014a1 ("test(x86_64): add host vs guest cpu feature test")
Signed-off-by: Takahiro Itazuri <itazur@amazon.com>

tests/integration_tests/functional/test_cpu_features_x86_64.py

@@ -343,7 +343,7 @@ def test_host_vs_guest_cpu_features_x86_64(uvm_nano):
                 "umip",
             }
         case CpuModel.INTEL_CASCADELAKE:
-            expected = {
+            expected_host_minus_guest = {
                 "acpi",
                 "aperfmperf",
                 "arch_perfmon",
@@ -392,19 +392,32 @@ def test_host_vs_guest_cpu_features_x86_64(uvm_nano):
                 "vpid",
                 "xtpr",
             }
+            expected_guest_minus_host = {
+                "hypervisor",
+                "tsc_known_freq",
+                "umip",
+            }
+
             # Linux kernel v6.4+ passes through the CPUID bit for "flush_l1d" to guests.
             # https://github.com/torvalds/linux/commit/45cf86f26148e549c5ba4a8ab32a390e4bde216e
             #
             # Our test ubuntu host kernel is v6.8 and has the commit.
             if global_props.host_linux_version_tpl >= (6, 4):
-                expected -= {"flush_l1d"}
-            assert host_feats - guest_feats == expected
+                expected_host_minus_guest -= {"flush_l1d"}
 
-            assert guest_feats - host_feats == {
-                "hypervisor",
-                "tsc_known_freq",
-                "umip",
-            }
+            # Linux kernel v6.6+ drops the "invpcid_single" synthetic feature bit.
+            # https://github.com/torvalds/linux/commit/54e3d9434ef61b97fd3263c141b928dc5635e50d
+            #
+            # Our test ubuntu host kernel is v6.8 and has the commit.
+            host_has_invpcid_single = global_props.host_linux_version_tpl >= (6, 6)
+            guest_has_invpcid_single = vm.guest_kernel_version >= (6, 6)
+            if host_has_invpcid_single and not guest_has_invpcid_single:
+                expected_host_minus_guest |= {"invpcid_single"}
+            if not host_has_invpcid_single and guest_has_invpcid_single:
+                expected_guest_minus_host |= {"invpcid_single"}
+
+            assert host_feats - guest_feats == expected_host_minus_guest
+            assert guest_feats - host_feats == expected_guest_minus_host
         case CpuModel.INTEL_ICELAKE:
             host_guest_diff_5_10 = {
                 "dtes64",