test: Reintroduce IA32_TSX_CTRL MSR exception

It is a known limitation where IA32_TSX_CTRL MSR cannot be restored,
although there is a room to dive deeper. Also, manage the exception list
separately for snapshot restore test unlike before.

Signed-off-by: Takahiro Itazuri <[email protected]>

Author: zulinx86

tests/integration_tests/functional/test_cpu_features_x86_64.py

@@ -251,6 +251,20 @@ def test_brand_string(uvm_plain_any):
 ]
 # fmt: on
 
+# A list of MSRs that are not saved into a snapshot, thus are not restored.
+# fmt: off
+MSR_SNAPSHOT_EXCEPTION_LIST = [
+    # It is a known limitation where MSR_IA32_TSX_CTRL cannot be restored.
+    # See https://github.com/firecracker-microvm/firecracker/pull/3182
+    #
+    # TODO: Dive deep into kernel behaviors around IA32_TSX_CTRL MSR.
+    # - https://github.com/torvalds/linux/commit/cbbaa2727aa3ae9e0a844803da7cef7fd3b94f2b
+    # - https://github.com/torvalds/linux/commit/7131636e7ea5b50ca910f8953f6365ef2d1f741c
+    # - https://github.com/torvalds/linux/commit/b9846a698c9aff4eb2214a06ac83638ad098f33f
+    "0x122",
+]
+# fmt: on
+
 
 MSR_SUPPORTED_TEMPLATES = ["T2A", "T2CL", "T2S"]
 
@@ -436,7 +450,7 @@ def test_cpu_wrmsr_snapshot(microvm_factory, guest_kernel, rootfs, cpu_template_
     snapshot.save_to(snapshot_artifacts_dir)
 
 
-def check_msrs_are_equal(before_recs, after_recs):
+def check_msrs_are_equal(before_recs, after_recs, snapshot=False):
     """
     Checks that reported MSRs and their values in the files are equal.
     """
@@ -448,6 +462,8 @@ def check_msrs_are_equal(before_recs, after_recs):
 
     changes = 0
     for msr in all_msrs:
+        if snapshot and msr in MSR_SNAPSHOT_EXCEPTION_LIST:
+            continue
         if msr in before and msr not in after:
             print(f"MSR removed {msr} before={before[msr]}")
             changes += 1
@@ -506,7 +522,7 @@ def test_cpu_wrmsr_restore(microvm_factory, cpu_template_any, guest_kernel):
     # Compare the two lists of MSR values and assert they are equal
     before_recs = read_msr_csv(msrs_before_fname.open())
     after_recs = read_msr_csv(msrs_after_fname.open())
-    check_msrs_are_equal(before_recs, after_recs)
+    check_msrs_are_equal(before_recs, after_recs, True)
 
 
 def dump_cpuid_to_file(dump_fname, ssh_conn):