fix(test): Remove ssbs from host-guest feature diff on ubuntu

Linux kernel should hide "ssbs" since Neoverse-N1 and Neoverse-V1 have
an errata whereby an MSR to the SSBS special-purpose register does not
affect subsequent speculative instructions, permitting speculative store
bypassing for a window of time. Not only our guest kernel but also host
ubuntu kernel (currently, v6.8.0-1016-aws) lack the change that hides it
while the Amazon Linux host kernels have it.

Fixes: 2babc80 ("test(aarch64): add host vs guest cpu feature test")
Signed-off-by: Takahiro Itazuri <[email protected]>

Author: zulinx86

tests/integration_tests/functional/test_cpu_features_aarch64.py

@@ -10,6 +10,7 @@
 
 import framework.utils_cpuid as cpuid_utils
 from framework import utils
+from framework.properties import global_props
 from framework.utils_cpuid import CPU_FEATURES_CMD, CpuModel
 
 PLATFORM = platform.machine()
@@ -82,11 +83,16 @@ def test_host_vs_guest_cpu_features_aarch64(uvm_nano):
     match cpu_model:
         case CpuModel.ARM_NEOVERSE_N1:
             assert host_feats - guest_feats == set()
-            # Kernel should hide this feature, but our guest kernel
-            # currently lacks the commit with this change.
-            # The commit that introduces the change:
-            # https://github.com/torvalds/linux/commit/7187bb7d0b5c7dfa18ca82e9e5c75e13861b1d88
-            assert guest_feats - host_feats == {"ssbs"}
+            # TODO: Remove "ssbs" once our guest kernel picks the following commit.
+            # https://github.com/torvalds/linux/commit/adeec61a4723fd3e39da68db4cc4d924e6d7f641
+            # See also https://github.com/firecracker-microvm/firecracker/issues/4898
+            expected = {"ssbs"}
+            # TODO: Delete "ssbs" removal once our host ubuntu kernel picks the following commit.
+            # https://github.com/torvalds/linux/commit/adeec61a4723fd3e39da68db4cc4d924e6d7f641
+            # See also https://github.com/firecracker-microvm/firecracker/issues/4898
+            if global_props.os.contains("Ubuntu"):
+                expected -= "ssbs"
+            assert guest_feats - host_feats == expected
         case CpuModel.ARM_NEOVERSE_V1:
             # KVM does not enable PAC or SVE features by default
             # and Firecracker does not enable them either.
@@ -97,9 +103,10 @@ def test_host_vs_guest_cpu_features_aarch64(uvm_nano):
                 "svebf16",
                 "svei8mm",
             }
-            # kernel should hide this feature, but our guest kernel
-            # is not recent enough for this.
-            assert guest_feats - host_feats == {"ssbs"}
+            # TODO: Remove "ssbs" once our guest kernel picks the following commit.
+            # https://github.com/torvalds/linux/commit/adeec61a4723fd3e39da68db4cc4d924e6d7f641
+            # See also https://github.com/firecracker-microvm/firecracker/issues/4898
+            expected = {"ssbs"}
         case _:
             if os.environ.get("BUILDKITE") is not None:
                 assert False, f"Cpu model {cpu_model} is not supported"